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JuanS, Ford Master Technician
Category: Ford
Satisfied Customers: 135
Experience:  Ford employed certified master tech 10yrs. ASE certifications, Think neighbor, Escape/Fusion Hybrid
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I have a 2003 Ford F150, 4.6L V6. What should the idle be

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I have a 2003 Ford F150, 4.6L V6.

What should the idle be when engine is warm? Mine shows 1000 rpm
What should the idle be when in drive? Mine shows 740 rpm

When in drive (vehicle not moving), I get a shutter. I replaced the IAC and cleaned the throttle body. Any idea on what this could be?
HelloCustomer Thanks for using

When your engine is warm and at idle in park or neutral, it will vary between 700-900rpm.

When you put it in gear the idle will drop a little to between 650-750 rpm maybe a little higher when A/C kicks on.

Common causes for a high idle would be a vacuum leak, it would also cause the engine to act funny when in gear, rolling idle or hesitation. You'll also hear a sucking noise.
The most common area for a vacuum leak was the pcv tube. If you find the pcv valve follow the tubing all the way to where it meets the intake. The rubber components will degrade over time causing a hole to form. This will create a vacuum leak. Look and listen for the leak.

The other common problem for high idle on 4.2L was intake gaskets leaking. The gaskets where the plastic intake meet the metal lower intake would leak. Also the bolts that would hold the 2 together would weaken causing a leak so you would replace the gaskets and the "isolator" bolts at the same time.
A way you can test for this is to buy some brake clean from the autoparts store (flammable). Get the engine to operating temp and then spray where the 2 intakes meet with brake clean. If the idle starts going up or down, you found your problem.
Be very careful not to spray it on the exhaust!!!

Hope this information helps you, if you need more please let me know!
If your satisfied with my answer then please click accept!

Customer: replied 7 years ago.

Have a follow up question.


If I disconnect the wire going to the IAC, what should the idle be? I noticed it dropped to about 840 rpm.


There is also an idle adjustment. I read on a forum, one must start the engine, remove the wiring to the IAC, then adjust the idle until 400-500 rpm is reached.


Can you comment on this also?



Hi ehaugn1, thanks for the question!

If you disconnect the IAC valve your idle should drop to around 400-550 rpm. Most cases it will even stall the motor.
If your idle is at 840rpm then you must have a vacuum leak.

The idle air control valve controls air getting into your motor. It is basically a valve that lets the air bypass the throttle body but is controlled. In fact they used to call the IAC a " idle air bypass valve."

So basically if you unplug it, it closes not allowing air thru. Since your idle is staying high (and not stalling), air has to be coming from someplace else. Like I said before, either the pcv tube or intake gaskets and bolts are the most common causes!

Yes you can adjust the throttle screw, and you might get the idle down a little more, but its not going to be right. Your basically putting a band aid on the cut, stopping the bleeding, but it will never heal. Also your this may have some adverse effects on the way your engine runs. Ford always tells us that should never have to mess with the throttle screw, if we do then you will start to have emission issues.

Yes that is the correct procedure to adjust the throttle screw. You should disconnect the IAC ( because you don't want the computer playing with the idle when your adjusting it). Turn the screw so the plate closes, till you get your desired rpm. Although with a vacuum leak you most likely will not get it that low!

Hope this information helps you, if you need more please let me know!
If your satisfied with my answer then please click accept!
JuanS and 2 other Ford Specialists are ready to help you
Customer: replied 7 years ago.

Hi Juan,


Could use your help again.


I looked all over and can not find the pvc tube. I also sprayed carb cleaner and did not notice any idle change.


The fan on the motor, I noticed it increased and decrease in speed. Is this normal or also related to my vacuum issue?


I recently purchased the vehicle. I removed the air cleaner element, looked fairly cleaned, but I blew it out with compressed air. Do you think this is related?


Also, I recently changed the transmission fluid. Drained anf filled via the fill tube. Just tought it's worth mentioning.



Hi ehaugn1

To find the pcv tube, just find the pcv valve located on the valve cover. Coming off of it will be a rubber tube running to the intake. Examine every rubber part of the tube.

Try disconnecting the idle air control valve like before, then spray the brake cleaner, where the upper part of the plastic intake meets the lower metal intake. Spray all the way around it and see if the idle changes.

Yes the fan speed can change, especially if the idle is going up and down.
Customer: replied 7 years ago.

I see one tube from each valve cover.


One tube goes to a large black tube, that goes to air filter.


The other tube connects close to the IAC.


I do not see a PCV valve. Is this vehicle suppose to have one?


Another question.


I have a service tachometer.


Want to make sure I have it on the correct setting

Which one is the correct setting?


1 Spark plug fires twice per revolution

2 Spare plug fires once per revolution

3 Spark plug fires every other revolution




If you look at the throttle body, to the left of it you should see something like this!graphic

I highlighted the tube that usually breaks, follow this tube back and see if you see any pieces ripped or broken.

You spark plug fires twice per revolution.

Is the check engine light on?

Thanks JuanS
Customer: replied 7 years ago.


Ok, I believe I know what tube this is. Has a bunch of foam/insullation around it.



Here is the Ford's service bulletin talking about replacing the intake gaskets, and bolts as I mentioned above. It is such a common problem there is a service bulletin and revised parts

TSB 05-22-06
Customer: replied 7 years ago.

I took a look at the PCV tube, removed it and thoroughly check it for cracks or breaks. Looks fine.


Thank you for the bulletin. I did spray and did not notice and idle change.


How can I accurately measure the RPM?


I have an inductive type of that wraps around one of the spark plug wires.



You should be able to clamp around any wire and run the tach to get an accurate reading.

Earlier you said you blew out the air filter, I'd like you to check a few other things,

1. Make sure the airfilter has no rips or tears in it, or the plastic nose cone is falling off.
2. When you have the air filter out look into the tube that goes towards the engine. In there you will see a peice sticking in to the tube. (maf sensor) Using a flashlight look at the sensor, you will see 2 little wires. See if there is anything stuck on the wires. Dirt, bugs etc... If there is, use some of the brake cleaner and spray the wires to clean them. make sure your truck is not on. When its clean wait for it to dry. Disconnect the neg battery terminal for a few minutes. When you start it again it will definately high idle for a few minutes untill it warms up. Once its warmed up the idle go to normal.
3.Check the wiring for the maf sensor where it leaves the tube. See if the rubber seal around the wires is still in place. It should seal the case so no air can get in thru the wiring area.

Also if you can give me your VIN# XXXXX can check to see if Ford has any service messages specific to your vehicle!
Customer: replied 7 years ago.

Hi Juan,


Here is the VIN, 1FTRF17203NB31651


Since I purchased the vehicle used, is there a way to find out if the service bulletin you sent me has been performed?


I could be mistaken here, but, prior to cleaning air filter, I do not recall having this issue, but I am not completely sure as I recently purchased this vehicle.



I searched your VIN and there is no messages regarding a high idle.

You truck has had no warranty work done to it. So unless it was done out of warranty or at an independent shop than it hasn't been done.

If it didn't happen till after you cleaned the air filter you might have done something to help cause this.
Check the things I mentioned above and make sure when you put the air filter housing back together that everything is sealed properly.

Customer: replied 7 years ago.
Should I purchase one of those diagnostic handheld computers?
You could, but your going to want one that reads data streams, which are usually pretty expensive,
You can go to places like Autozone, they usually will pull codes for free if there are any.
Customer: replied 7 years ago.



Couple more questions.


The IAC, if I turn on the ignition, engine not running, should I see the IAC pluger move?


Where is the OBD port located? Do OBD devices measure RPM?


Yes i believe it will move, quickly then stop.
The obd port is located right underneath the steering column.
It will look like thisgraphic

A good obd scanner will let you read live data, like rpm. but it is more expensive. Probably cheaper to take it to a shop!

Customer: replied 7 years ago.

Hi Juan,


Have a few more questions.


When the vehile is running, I reach into the engine compartment and manually pull on the accelerator. By doing this, I notice the engine runs high for a few seconds, then the idle drops back down. Is this normal or should it drop down immediately?


So, back to original issue. I noticed tonight, the vibration only occurs when the engine is warmed up (normal operating temperature), brake is applied and the vehicle is in drive.


Is does not occur when the vehicle is first started or within the first 5 minutes.


With this new information, do you have any other thoughts?




Customer: replied 7 years ago.
To add regarding the transmission, the oil was recently changed, only have 10 miles. Vehicle has 75K. Will the vibration lessen as the oil "breaks in"?
HiCustomerbr />
Yes the engine shouldn't come down real quickly, but it shouldn't hang up at a high idle for longer than a second. If its hanging up high then thats another sign of a vacuum leak.

As for the vibration, when you first start up the truck its going to high idle for a little to warm up, then the idle will drop to normal. The high idle might be covering up the vibration on startup till it dips to a normal idle.
You might want to see if you can find another 4.2L and sit in it to compare. The 4.2L does have kind of quirky idle, if your not used to it.

Also your trans fluid should have nothing to do with an engine vibration, so if its vibrating in park, or neutral, most likely its not gonna be an issue.

Customer: replied 7 years ago.

Thank you for all your updates.


It does not vibrate in neutral or park.

No problem, If it were me, and I had your truck in the shop right now, I'd probably try to compare it to another 4.2L to see if it feels the same. You might be trying to fix something thats a normal characteristic of the truck.
Also you still might have a problem with the Intake gaskets, its just too common of a problem to ignore! Even though the idle didn't change when you sprayed brake clean, there still could be an issue.

Customer: replied 7 years ago.

Ok, think I am going to order th gasket and replace it.


Where you located out of?

I'm in tampa Fl

Dont forget about the bolts!!

Edited by JuanS on 9/25/2009 at 3:02 PM EST
Customer: replied 7 years ago.

I will most likely replace the gasket and bolts sometime next week.


Last night, I cleaned the EGR. Did not look bad.


I also removed the throttle body and cleaned it again. Wanted to clean the flap and check the insides again. It is not thoroughly clean.


Did not have any change with the vibration in drive.


Good suggestion on the comparison. Hopefully I can find one to take a look at.


I am thinking about replacing the spark plugs and air filter today, since I really do not know the history. Anything else you recommend since it has 75k on it?



Spark plugs are supposed to last to 100,000m but I usually recommend to change them around 80,000m so if your close to that then change them. Air filter and fuel filter will be good idea. You will need a special tool to get the fuel filter off, if you wanted to do that. Its a fuel line quick release tool, they sell it at autozone.

Other than that the 4.2L is a pretty durable engine, just keep up on oil changes!

Thanks JuanS
Customer: replied 7 years ago.



Do you have a service/maintenance interval guide that you can send me?


Thank you for all your help. I will soon have this all figured out.


Would like to send you some more money since you have been most helpful.


What do you thnk is a fair price?


I appreciate the gesture and any amount you feel is appropiate, I will appreciate.

Do you have the service manual for your truck it should be in there, if not let me know, I might be able to get it for you!

Customer: replied 7 years ago.

The truck did not come with any manuals.


I found an electronic copy of a 2003 owners manual, but did not have any service guide.



Ok well here's Ford's maintenance schedule. It's supposed to be for the F150, it's pretty generic though. I think they put the same one in most cars and trucks.

Maintenance Schedule

That should be what you need.

Customer: replied 7 years ago.

Thank you.


Do you think I should replace the spark plug wires and cap?


I did not see anything for this in the schedule. Only the spark plugs.

There is no cap, your truck is distributorless, if the wires look old, cruddy then yes replace them, but make sure you do it one at a time!!!! If you don't and miswire the ignition your going to be worse off!

JuanS and 2 other Ford Specialists are ready to help you
Customer: replied 7 years ago.
Sent you some additional cash for your time and assistance.
Thank you very much!!
Customer: replied 7 years ago.

Hi Juan,


Here is an update.


I have replaced the spark plugs, gapped them to .054".


Replaced the air filter


Cleaned the MAF


Same issue.


Since I really have not driven the car much, I decided to take it out for an hour today. I noticed after about 10-15 miles, it did not happen.


I also noticed that if I turn off the vehicle after driving it for a while, then wait for a few mins, then start and drive vehicle, it would not happen.


I will eventually change the intake gasket, but wanted to privde you more information.


Any thoughts?


I have some vacuum gauges, any idea on what the vaccum should be at idle? Where would I plug the gauge into?



Makes me think the gaskets are bad, You see, when the plastic intake and metal intake contract and expand as the engine gets colder or hotter. When the engine is cold, the the plastic has contracted and metal intake has contracted, leaving openings for a vacuum leak, once the truck is hot the plastic intake and metal intake have expanded filling in the gaps and getting rid of the vacuum leak.
4.0 explorers were even worse.. when it was cold the leak would be so bad it had a hard time starting, but once it warmed up and everything sealed, you couldn't tell anything was wrong with it. Replace intake gaskets, problem solved.

Vacuum reading can be taken anywhere you have a vaccum. Readings should be around 17-19 in.

Hope that helps you
Customer: replied 7 years ago.

Hope to replace it this week then. I have been learing much about this vehicle, it has been a fun project.


While I have the manifold apart, anything else worth replacing or inspecting?


For the rear differential, they call for a 75w140 gear oil. Do you suggest I replace it?

First, there are going to be a couple of hard bolts to get to on the back of the manifold, near the firewall, just to give you a heads up. You'll know it when you get to them. Some people have removed that flame retardant material on the firewall to give them a little more room. While your in their examine the egr ports. Inside the intake passages you'll see a little port in each one. Make sure they are not clogged up. Use a pick or tiny screwdriver to poke the debris out, if there is any.
Here is a pic of the installation sequence of the bolts and torque specs, make sure you get the bolts. The part number is XXXXX the tsb i uploaded above.graphic

Yes that is the correct gear oil, with your current mileage it couldn't hurt!


Edited by JuanS on 9/28/2009 at 12:19 PM EST
Customer: replied 7 years ago.

Thank you.


Will pick up gasket and bolts this evening.


Any other gaskets worth replacing sine I have it apart?

You can get the top intake gasket, its 1 long rubber gasket that goes between the top of the intake and the middle. If you look at the bolt picture above, this gasket goes around the edge of that manifold.
Customer: replied 7 years ago.

Hi Juan,


Wanted to provide you an update.


Purchased 6 intake port gaskets, 8 bolts (green) and the upper intake gasket.


Removed the intake last night and replaced the 6 intake gaskets and 8 green bolts. The lower intake was dirty, especially by the front 2 ports. All the gaskets were dirty on both sides. I cleaned the entire housing and the ports.


I need to install the intake cover with the 10 (or 12) bolts. Do you know what the correct torque setting should be?


I also used a wooden skewer stick and cleaned out the 6 EGR ports.


Really hope this fixes the issue.

I usually just tighten those till they are snug, working from the middle outward.

I hope so too!
Customer: replied 7 years ago.

Hey Juan,


Here is an update.


Put it all back together, same issue.


What should I do next?


Back to the IAC. I checked and there is 11.79 volts at the connector, engine off, ignition ON.


I removed the IAC and did not see the plunger move when I plugged in power. Is it suppose to?



HiCustomerbr />
The IAC is commanded by the pcm (or main computer). It should move a little when you plug it in, depending on what the pcm is trying to do. A better test is to have the truck running and unplug it. If the idle drops or engine stalls, your IAC is working.

Did you disconnect the battery when you replaced the intake because the pcm is going to have to relearn strategy which means you might have a little high idle.

Are you still having a high idle problem, or is this just a vibration issue?
Customer: replied 7 years ago.

Hi Juan,


Battery was disconnected when I replaced the manifold gaskets.


I tried another new IAC and it had the same behavior.


I removed the IAC to see if the plunger moves when I turn on the ignition, and it does. It has the same behavior as the old and new. It moves about 1/8" open for 2-3 seconds, then closes. I hear a "click" noise in the IAC when this happens.


I did unplug it as the engine was running, the RPM stayed the same, no change.


Also, keep in mind, I am not driving the vehicle, I start it, wait for it get to normal temperature, then place the vehicle in drive or reverse.


Replacing the gaskets I believe did help, but the vibration still persists.

Does it still high idle, or just vibrate,
if it still high idles, I wonder if somebody messed with the throttle screw to boost the idle.
Sometimes when the IAC would stick it would cause a low idle or stalling, and people with some mechanical experience would open the throttle plate more to compenstate.

You might want to try moving the screw with the IAC unplugged until your idle drops to 550 or so.
Customer: replied 7 years ago.

I believe it is idling fine. But, I can not be sure what it is idling at? My gauge shows 620. But, not sure how accurate it is. Any idea on what I can use to accurately measure the idle?


Ok, I will try the idle screw this evening.


Back to the transmission fluid change. It was removed from the dipstick, filled, then engine was run and gears where changed. Then fluid was removed again, then filled.


My memory could be wrong, but I believe I noticed it after the fluid was changed.


Does the new fluid have to "break in" or something like that? I have read something to the affect, that trans fluid changes could cause issues. Maybe by putting the vehicle in drive, the torque converter is not engaging properly at low idle?


Grasping here.



No, trans fluid won't cause a vibration, new or old.

You could try taking the the serpentine belt off, to see if its one of the accessories that is causing the vibration, like a unbalanced alternator. Just don't run it to long without the belt on, cause it will overheat( no waterpump)

Other wise your gonna need to compare this to another and see if they are the same!

Customer: replied 7 years ago.

Do you think replacing the fuel filter would help?


Could this be a possible cause?

Not likely the cause, but if it hasn't been replaced then its a good thing to replace.
You will need a special tool to change it, Fuel Line Quick Release tool for Ford. Should have it at the auto parts store.
Customer: replied 7 years ago.

Hey Juan,


Could it be a bad fuel injector?


How can I check them?

It could be a bad injector, they used to have a problem with them back around 2002, they would stick on start up, but once they were warmed up, they'd be ok.
I can't think of a safe way for you to test them. At the dealer our scanner will run a fuel injector flow test and help to determine a faulty injector.
You would have tom make sure they were tested cold too.
If I remember we were able to clean the injectors out using injector cleaner, you might want to try getting a bottle and running it thru the system. Get something decent to try.

Customer: replied 7 years ago.

Hi Juan,


Got a good injector cleaner, maybe this will fix it.


I played around with the throttle plate screw. Backed it all the way out, very slight change in RPM. Took it for a test drive, actually vibrated worse, so I put it back to where it was.


Question. I disconnected the tube going into the PCV valve. It has very good suction. By doing this, I noticed there was no change in RPM.


Another question. I noticed I get some water out of the exhaust. A few drop or more. Is this normal? I notice to collects at the end of the tail pipe.

Hi, ehaugn1

If you removed the tube, its a rather big tube, the vehicle should stall out. You just induced a huge vacuum leak. If it didn't then you might have something wrong with the mass air flow sensor. Have you tried running it with the mass air flow unplugged, to see if vibration changes? If not, then try it.

Yes it is very normal to get water out of the exhaust, water is a natural by-product of combustion.

Customer: replied 7 years ago.

Hi Juan,


Here is an update.


I disconnected the MAF. Started the engine, inital RPM is 850, then over the course of 1 minute, dropped to 620, car was in park.


I reconnected the MAF, started engine, inital RPM is 850, then over 1 minute, it dropped to 620 again, car was in park.


For both tests above, I disconnected and connected the MAF when engine was off, did not disconnect battery.


Any thoughts on this?

Well thats pretty normal, all Ford vehicles idle high for a minute or too, depending temp. Then go to a more normal idle. 620 might actually be a little low for it being in park, should be around 720 in park.. 650 or so in drive.

MAF may be an issue, but its not showing a problem with this test.

Maybe you can bump up the idle screw a little to see if it helps, but not too much. If you go to much the throttle positon sensor will think your stepping on the gas and it will automatically high idle.
Customer: replied 7 years ago.

I assume I do this with the engine running?


Could it be a problem with the PCM?


Is there a way to reset the ACM?

Yes, with engine running,

Yes could be, not very likely. There is no good way to test a pcm either. You basically test everything else, and if you find nothing wrong with everything else then the computer is probably at fault. Ford doesn't make a tester for the computer, or any easy way to test it.

If you mean reset the pcm, yes you can disconnect the battery for a few minutes and that will reset the keep alive memory in the pcm. ACM is audio control module, (radio)

Customer: replied 7 years ago.

Hey Juan,


Here is the latest. I turned up the throttle about 1 full turn. Idle is now 700.


When placing it in drive, it idles is now 550. Much better, vibration is pretty much gone. I do hear a ticking noise though, when I press the accelerator slightly, it goes away.


So, how can I be sure the idle screw is set correctly?

Usually i would look at my scanner while adjusting the screw to make sure the voltage is between .85-.95v at idle, careful to not go over.

If you do go over, then your idle will stay permanently high, over 1000rpm because the computer is thinking your applying the gas so it boosts up the idle a little using the IAC.

To be absolutely sure its set correctly you would need a scanner to set the tp voltage.

Customer: replied 7 years ago.

Hi Juan,


I am going to compare the vehicle idle to another one this weekend. In speaking with the person, sounds like the behavior is common.


If you don't mind, I have a steering question.


When driving I noticed I have to make slight adjustments, left and right, with the steering wheel to keep it driving staight. I have replaced the tires and the alignment is dead on.


I did not see any play in the tie rods or ball joints.


Any ideas on what it could be? Does the steering box have a worm gear that can be tighetened up?



Hello ehaugn1

If you don't have any play in the tierods or ball joints, I believe there is an adjustment for the steering gear. Unfortunately I'm not the guy to ask! I primarily work engine driveability, electrical systems, and electronics. You'll probably want to ask this question on the site to get the correct expert to respond.

Thanks again
Customer: replied 7 years ago.

Hi Juan,


Could use your help again.


Still playing with the vehicle.


I noticed I am getting water and black soot from the tail pipe and from other parts of the exhaust, cat converter and where some of the pipes join.


Is this normal? What causes this?


Also, I measured the TPS, at idle, it is 1.0 Volts at 700 RPM.


If I disconnect the IAC, there is no change in the RPM. I did the ohm test and it looks fine based on what Chiltons tell me it should be.

HiCustomerbr />
yes, the water and soot is going to be normal. Water is a natural byproduct of combustion. When the gas is burned the result you get is energy, CO2, CO, NOx, H2O (water) and others. You'll get some black stuff also.

The tp voltage should be a hair lower, I like it around the .9 to .95 range. 1.0v is getting kind of high.
Customer: replied 7 years ago.

Ok. I will take a look at the TP voltage. To adjust this, do I need to disconnect the IAC or it does not matter?


I think if I adjust this, the RPM may be too low, it is current at 700 RPM at idle.


Any thoughts?



No it doesn't matter.....If the idle is good and not high then you should leave it alone. If it seems to come to a high idle on its own or will stay at a high idle when you let off the gas then adjust the t.p down.
Customer: replied 7 years ago.

Hi Juan, Ok, here is the latest.


I set the TP sensor to exactly 0.95 volts.


I decided to look at the IAC again.


(Ignition on, engine not running) I removed the IAC with the harness still attached and back probed the connector. I noticed there is no voltage. I do get volatage if I disconnect the IAC, it is around 11.8 volts.



I then did the following:

Removed negative battery connector

IAC with harness attached and back probed into harness, volt meter attached

Attached negative battery connector

Checked voltage, jumped to 12 volts and I see the IAC plunger moved 1/8" for 2 seconds

Then voltage dropped to 0 volts and plunger closed


Is this information helpful?


Next I will check voltage with engine running.

Customer: replied 7 years ago.

Hey Juan,


Here is another update.


After changing the TPS to 0.95 volts, the idle in park is 600 RPM.


With the engine running, I removed the IAC wiring harness, it showed 14.4 volts. When I unplugged the wiring harness, there was no drop in RPM. When I plugged the harness back in, there also was no change in RPM.


I then backprobed the wiring harness for the IAC. At 600 RPM, it showed 2.8 volts.


If I increased the idle to 2000-3000 RPM, the IAC voltage dropped to 1.8 volts.


Any of the information helpful?

Customer: replied 7 years ago.

Hi Juan,


Brought truck to shop today. They could not find anything wrong. Turns out, my tachometer was not correct.


At idle, based on the OBD port, it is 800. In drive, it is 620.


All the sensors checked out fine.


The noise may be coming for the exhaust or the engine mount.


Any thoughts on this?

HiCustomer I'm sorry I didn't see your other posts!
I'm glad your truck has a normal idle. The obd port or reading rpm straight from the computer is your most accurate reading.

It is not common for your truck to have failing motor mounts, but age will play a factor. It is possible to have a broken exhaust hangar causing a vibration or buzzing.

Customer: replied 7 years ago.

Hey Juan,


I spent some time under vehicle, engine running and in drive (had to trust the wife with this one). I did not see any broken engine mounts or broken exhaust hangers.


I did see the exhast muffler vibrate some. I could pull the exhaust either left or right, and it did make the vibration less.


Also, I noticed a pinging noise just below the right side exhaust manifold, near where the catalytic converter. Could I have a bad oxygen sensor?


Thankgs again



Hi erick,

If you were able to make the vibration change by moving the exhaust around then thats most likely the problem. If your positive the hangars are ok then I would "Neutralize the exhaust"

What you need to do is loosen the exhaust, don't take it apart, but loosen the clamps and attaching hardware after the manifold. Then start the truck and let it run for a min, move the gear shifter from p to r to n to d, then d, n , r, p. Do this again and end in N. Then tighten all the clamps. See if the vibration is gone.

I doubt you have a bod o2 sensor, maybe the internals on the cat are broken.
You would have to take the cat off and look.

Customer: replied 7 years ago.

Ok, hope to look in the next day or 2.


Any idea on why this would happen when vehicle is at normal temperature?



No, I am not sure why temp would change it.
Customer: replied 7 years ago.

Hey Juan,


I purchased a AutoLink OBDII reader. See below results, I am curious what you think.


TP (Absolute Throttle Position) % is 19.2

O2B1S1 (Oxygen Sensor, Bank 1, Sensor 1) fluctuates between .10 thru .745 volts

O2B1S2 (Oxygen Sensor, Bank 1, Sensor 2) .785 volts

O2B2S1 (Oxygen Sensor, Bank 2, Sensor 1) fluctuates between .08 thru .750 volts

O2B2S2 (Oxygen Sensor, Bank 2, Sensor 2) .675 volts

SHRTF1B1S1 (Short Term Fuel Trim Bank 1, Sensor 1) % fluctuates between -3.1 thru 2.3

SHRTF1B2S1 (Short Term Fuel Trim Bank 2, Sensor 1) % fluctuates between -3.9 thru 2.3

These readings are perfect. o2b1s1 (oxygen sensor bank 1 sensor 1) upstream
o2b2s1 (oxygen sensor bank 2 sensor 1) upstream should fluctuate between 0 and 1 volt. 0 means lean 1v means rich.

o2b1s2 bank 1sensor 2 downstream, o2b2s2 bank 2 sensor 2 downstream. These are your catatlytic converter monitors. The just tell you how your cats are performing. The should stay flat somewhere around .5v but can go higher or lower. The important thing is that they do not look like a fluctuating oxygen sensor. If they do then the cat performance has decreased.

Short fuel trims should be around 0% but will fluctuate. If the percentage gets above +- 13 then you might have problems with fuel control.

Your numbers look very good.

Customer: replied 7 years ago.

Hi Juan,


Took a break from the F150. Will get back to it this week. I will "neutralize" the exhaust, probably tomorrow night.


Just to confirm, do you believe 620-640 RPM in drive is correct?

It should be around that area 650 +-XXXXX
Customer: replied 7 years ago.

Hi Juan,


Took a look at a 2003 F150, V6, 4.2L, 118k miles today.


Have some updates for you. All the measurements I gave you match the vehicle I checked out today (throttle position sensor, O2 sensors, engine RPM in park and in drive are identical).


The vehicle with 118k, did not have any vibration that I am experiencing.


Here is the only difference.


If I unplug the IAC on the vehicle with 118k miles, the engine drops to 520-550 RPM.


If I unplug the IAC on my vehicle, there is no RPM droppage.


I am going to swap IAC and see how the truck reacts.


Any thoughts on this?





Customer: replied 7 years ago.

Hey Juan,


Here is another update.


I took my IAC and placed it into the vehicle with 118k miles. Appears my IAC is working fine. If I unplug it, then the idle dropped to 550 RPM in the vehicle with 118k miles.


I have peace of mind that my IAC is fine.


So, wondering why when I unpug the IAC on my vehicle, the engine RPM does not drop.



Customer: replied 7 years ago.

Hey Juan,


Have another question, could it be something with the transmission/torque converter at this point? Maybe the torque converter is engage at a lot RPM when it should not be?


Anyway to check this?

Hi erik,

So the your readings match the other truck, and your IAC works. Thats some good news. If you unplug your IAC and the vehicle doesn't drop Idle, then the only thing I can think of to keep the idle with out the IAC is a vaccuum leak. With your scanner can you check LONGFT1, LONGFT2 and IAC duty cycle? If so check them out. Your long fuel trim should be around 0% like the Shorts, If they are high like +15% or more than you have a vacuum leak. If your IAC duty cycle is low like 15% than the computer is trying to lower the idle and can't do it. IAC duty cycle should be around 30%.

Since the vehicle only does this with the truck in drive, then you may have a problem with the trans but it not likely, you mostly get a stall, or a dip in idle if the converter is doing something unintended. A higher idle is not likely.
Customer: replied 7 years ago.

Ok, I will take a look this evening. I do not believe I have a read out for IAC duty cycle.


Also, when checking, should I have the vehicle in park or drive?

Try it in D
Customer: replied 7 years ago.

Hey Juan,


Both Long Term Fuel Trim Bank 1 and Bank 2 had the same readings. It started out at 0.0 and stayed there for about 5 minutes, then moved to 1.6, then to 3.1 at operating temp. If I press on the accelerator, it would decrease to 1.6 then 0.0, then back up to 3.1. I did this in both park and drive, same results.


I do not have a reading for IAC duty cycle.


I did unplug the IAC again, no drop in RPM at all. I thought about removing the IAC and blocking both ports in the manifold and see if it makes a difference. Any thoughts?


Inside the engine compartment, if I press the accelerator with my hand, I hear a big sucking sound, I think this is normal since the engine RPM is increasing and it demands more air. Although, the engine tends to "run-on" for a few seconds.

Customer: replied 7 years ago.

Hi Juan,


Here is another update.


I decided to measure the vacuum. It is 19 in HG, dead on, no fluctuation. According to Hayes manual, should be between 17-22 in HG.


I snapped the throttle open and closed quickly, vacuum dropped to 0, the jumped to 23, then after 4 seconds, back to 19. So, I think the vacuum should be fine.


Here is something interesting though. When I placed the vehicle in drive, the vacuum dropped to 17. Is this correct?


Thanks, XXXXX XXXXX a nice Thanksgiving.

Vacuum readings are correct. I'd like to know what happens when you block of the IAC. Your truck shouldn't run, or run low idle.

Hope your thanksgiving was well!

Customer: replied 7 years ago.

Hi Juan,


I blocked the IAC port, started the vehicle and it idled at 800-830 rpm. I did not press on the accelerator.


Hope this information is helpful.


I am at a complete loss on what to do next.



That is weird, you have to be getting air from some place else. Try blocking off vacuum lines going to the intake. Try the pcv valve first. Pull it out and block it off. If it doesn't change it, then try the other lines and block them off to see if any change the idle. Do it with the IAC unplugged. That should aid in discovery of which component is allowing air to get in.
Customer: replied 7 years ago.

Thanks Juan, will check it out on Friday and post my findings.


Sorry this is taking soo long to resolve.


Do you have a cell phone? If so, who is your service with? I work for AT&T, let me know if you need anything.



Thanks I appreciate that, but I'm with sprint.. just got the htc hero, its a cool phone!

Customer: replied 7 years ago.

Hi Juan,


Here is the latest.


I plugged the PCV (PCV still attached as there is a coolant that runs thru it), plugged the brake port and the port in front of the brake port, IAC wire disconected, still ran at 800 RPM.


While running, I removed the air filter snorkel going to the throttle body, it ran rough for a second then died.


Here is what I also noticed, with the IAC wire attached, I would start the vehicle, then immediately removed the IAC wire, the idle would drop. If I attached the wire, it would ramp up. After about 2 mins, unplugging or plugging in the wire for the IAC has no affect. This is the same regardless if the vechile is warm or cold.


Any of this information helpful?

Customer: replied 7 years ago.

Hey Juan,


I took the day off today. Anything else I can check today on the vehicle?

Can you try turning down the screw on your throttleplate a little. Do it with the IAC unplugged. Make sure your turning it in the direction so that your plate closes. Tp voltage shouldn't be higher than a volt. Also when your done adjusting it, disconnect the battery for a few minutes to reset the computer. See if this will bring your idle down. A scanner that can read tp voltage and Iac duty cycle would be a help!
Customer: replied 7 years ago.

I have a voltmeter and can pin probe the TP harness. Will this work? It is currently set to .95 volts.


The ODBII device can read absolute throttle position as a %, currently set to 19.2.



yeah you can back probe the tp. .95 is within spec but you can lower it. Take it down and see if you can get the engine to almost stall with Iac unplugged.
Customer: replied 7 years ago.

Hi Juan,


Here is the latest


Vehicle cold.


Engine off, I loosened the screw where it did not touch plate, lowest reading is 0.89 volts, would not go any lower. I then turned in screw until I reached 0.90 volts.


I then removed negative battery terminal for 15 minutes.


Intalled battery terminal and started vehicle, once warm, idled at 830, same as before.


I then removed the IAC harness, idle dropped 100 RPM, approximately 700-730. I then installed wiring harness and it jumped to 1000+ RPM, then settled back to 800-830 RPM.


I then placed vehicle in Drive, got a lot of vibration.


Where do I go from here?



Customer: replied 7 years ago.

Hey Juan,


Have another update. I think we are close to getting this figured out.


Took vehicle for test drive, once it warmed up, there was much vibration in the engine, where I felt it in the vehicle, the original problem I am trying to solve.


I then turned off igntion, started it immediately back up, placed it in drive (break applied, vehicle not moving), no vibration until 60 seconds later. I have done this 3 times and the pattern is the same.


Does this information help?

After 60 seconds I believe is when the truck switches to closed loop operation, which means its looking at the o2 sensors and adjusting according to their input as opposed to running in open loop, which is preprogrammed values.

Try to increase the throttle just to the point where the vib goes away. Then disconnect battery again to reset computer.
JuanS and 2 other Ford Specialists are ready to help you
Customer: replied 7 years ago.

Hey Juan,


Here is an update. So, I bumped up the throttle just enough where the vibration goes away and reset computer.


Huge difference. In park, idle is 880-830, in drive idle is 680-730.


The absolute throttle position is 19.8 %. The throttle position voltage is 0.98


Any thoughts based on these readings?


Want to spend you some more money for all the time you spent on this.


Have another question. I believe I have a slight oil leak on the oil pan rear seal. Is this a common problem? I have the 2WD, do I need to remove the support to remove the oil pan?



Customer: replied 7 years ago.

Hey Juan,


Just sent you a few more bucks. Please take a look at my questions from the other day.


Thank you

Sorry for taking so long, been hectic at work. The readings you have look really good. As long as your fuel trims are still ok then your right where you need to be.

Give me a few minutes and I will check the procedure for replacing the oil pan gasket.


Here is the procedure. It tells you to pull the motor, but if you have a soft rubber gasket. Then you can just drop the pan and cut the old gasket out and kinda stretch the new gasket around the oil pan to get it where you need it.


Oil pan procedure<-----click



Customer: replied 7 years ago.

I will send you all the reading I get off the OBDII device in the next day. Can you take a look and let me know what you think?


For the readings, should I give them to you while vehicle is in Park or Drive?


If you have an email, I can send you the spreadsheet I am putting together.



I do have an email, but we are not allowed to exchange that on this site.

readings in drive would be better!

Customer: replied 7 years ago.

Ok, here are the readings with vehicle in Drive, vehicle not moving.


Let me know what you think or have any concern.


TP (Absolute Throttle Position) %19.60%
O2B1S1 (Oxygen Sensor, Bank 1, Sensor 1)0.080 - 0.750 V
O2B1S2 (Oxygen Sensor, Bank 1, Sensor 2)0.450 - 0.625 V
O2B2S1 (Oxygen Sensor, Bank 2, Sensor 1)0.080 - 0.750 V
O2B2S2 (Oxygen Sensor, Bank 2, Sensor 2)0.565 V
SHRTF1B1S1 (Short Term Fuel Trim Bank 1, Sensor 1) %-3.1% - 3.9%
SHRTF1B2S1 (Short Term Fuel Trim Bank 2, Sensor 1) %-3.1% - 3.9%
LONGFT1 (Long Term Fuel Trim Bank 1) %3.10%
LONGFT2 (Long Term Fuel Trim Bank 2) %4.70%
Spark Advance o12o
ETC (Engine Coolant Temperature) oF194o
Load PCT (Calculated Load Value) %10.60%
MAF (Mass Air Flow Sensor) Lb/Min0.75 Lb/Min

The values you are showing, look really good.

O2b1s1, o2b2s1 should be switching between 0- 1v
o2b1s2, o2b2s2 should be sitting steady around .5v
Shrtft should be around 0% if they start getting to +- 12% thats when you start to have a problem, usually the checkengine light will come on.
Lngft is the same as short. Yours looks really good.

I can't see any kind of issue with your vehicle looking at this data. If it were in my shop, I would tell you everything checks ok!

Customer: replied 7 years ago.

Ok, I will keep it as is and just keep an eye on it.


Thanks for all your help.



No problem, anytime!
Customer: replied 7 years ago.

I will be in Orlando next week.


Thought about bringing vehicle to you to check out if you have an interest.


Any thoughts?

I wouldn't mind lookin at it, if you were swingin towards tampa.
Customer: replied 7 years ago.

Ok, that would be great.


Do I need to setup an appt with you?


Pls send me address or dealership name to I can map it out.


thank again.

Just call the Dealership and ask for me. The dealership is in my profile. Just click on my name below and that should bring you to see my profile.

Customer: replied 7 years ago.

Hey Juan,


I will be driving to Orlando on Monday to see my parents. I would be willing to stop by your dealership if you have time to do some further troubleshooting. You mentioned there are other tests that could be run, like duty cycle for IAC. I am sure your dealership has more advanced diagnostics tools than I?


I would drive down to Tampa on Tuesday morning, Dec 15th if that would work for you. Let me know as I would make this trip if you are available.


Thanks again.

I am available but, I won't be able to spend lots of time with it, hour at the most, but I can definitely look at it. Tuesday is the busy day of the week.

You can just show up to the dealer sercice department and ask for me.

Customer: replied 7 years ago.

That would be great.


Send me a time and I will plan accordingly.

any time is fine. except 12-1pm thats my lunch
Customer: replied 7 years ago.

Hey Juan,


Hope you had a nice weekend.


I am still on schedule for tomorrow. Should be there around 9:30 or 10.

Sounds good!
Customer: replied 7 years ago.
Hi Juan,

Nice meeting with you on Tuesday.

I looked up the warranty and called Ford also. You are correct, 8 years or 80k for the PCM.

Can I ask you a favor. Can you write up a few paragraphs on our findings and leading up to possibly being a PCM issue? I want to be accurate when presenting this to my dealership in Atlanta. I plan on bringing it in on Monday and want to be prepared.

Thanks again.
Sure thing,

First, IAC duty cycle is way too low. The PCM is unable to control idle using the IAC valve. This is further confirmed by unplugging the IAC and the rpm does not change, either does the IAC duty cycle.

With the throttle plate fully closed and fuel trims normal then the vehicle would have to have an internal vacuum leak. When you disconnect the vacuum line from the Vapor management valve to the intake and block it off, the computer is able to control idle again and adjusts accordingly. This shows that the leak is coming from the Vapor Management Valve. When monitoring the valves duty cycle, it is being commanded to over 90% at idle in park or in gear. This command is what causing the internal vacuum leak. When you unplug the Evap Vapor Management Valve the problem goes away.
In my opinion the PCM is erroneously commanding the Vapor Management valve on causing the idle and vibration concern.

Hope that helps you, if you need more let me know...

Customer: replied 7 years ago.
Hi Juan,

I wrote up a letter and will provide it to Ford dealership on Monday. Are you comfortable with me providing your name and contact number? Not sure they will call. If you are, what is your last name and best contact number.

Thanks again for all your help.
Sure, you can call my work any time during the day 8am-5pm on monday. Just ask for service, and Juan. Im the only Juan here.
Customer: replied 7 years ago.
Hi Juan,

Have an update for you. I decided to test the vapor management valve. It appears the valve is working properly. With no voltage applied, the valve is closed. With voltage applied, the valve opens.

After running these tests and disconnecting the negative terminal, I decided to disconnect the IAC, sure enough, the RPM dropped, and raised when I plugged it in. I performed this a number of times, and had the same results.

The end result, I still have the vibration.

I still plan on taking it to the dealership on Monday.
Customer: replied 7 years ago.
Dropped off truck at Peachtree ford. Hope they get this resolved. If the pcm needs to be replaced, is any calibration or adjustments need to happen? They also mentioned each pcm is unique to the vin. Is this true?
The vehicle gets programmed at the dealer when they put the new PCM in. The PCM does need to be programmed to the vehicle which will make it unique to the vin when its programmed. The PCM is not unique when you first get it out of the box. Many trucks have the same PCM its the programming that sets it apart.
Customer: replied 7 years ago.

Hey Juan,


Just spoke with the dealership. So far, they claim that the vibration is from the motor mounts. They are still investigating.


But, if I turn off the vehicle, start it right up, no vibration until 2 minutes later, so, do not think this is the motor mounts.


They also claim they are not seeing a high duty cycle. Any thoughts on this? Anything specifically I need to tell them to look for?

Ask them why then does the idle drop when the VMV is unplugged, and why is the duty cycle at 90+% at idle in gear. If they can't see the high duty cycle then they are not looking. If you want, go there and have them pull up the Senosor readings in front of you like I did. Tell them you want to see the Evapvmv pid. This should never be at 90% or more. And the IAC pid should be at 30% -40%, not 13%.

About the motor mounts, I said they might be weak too, but that doesn't explain the IAC duty cycle at 13%.
Tell them to look harder, its obvious they are not trying, or even hooked up a scan tool.
Customer: replied 7 years ago.

Hey Juan,


Here is the latest. They could not definitely determine what the issue is, PCM or not. The are keeping the vehicle over night and will take another look tomorrow morning. They want their foreman to take a look tomorrow as he is off on Mondays.


They also said, Ford will not let them replace the PCM unless they have hard evidence that this is what the issue is.


Hate being caught in the middle.


Anything else you can suggest I could push forward with? This is why I hate bringing vehicles to the dealership.



Good let them take a long look at it, and hopefully the foreman has some training. As for needing "hard evidence" thats bs. They just aren't sure whats goin on. The sad part is that there is no specific test to diagnose a PCM, You test everything else and if it checks out then you replace the PCM and see if it fixes it.

Not much else I can tell you, just keep pushing them and ask why evapvmv is so high and IAC duty cycle is so low. When you unplug VMV then IAC returns to normal! The computer is commanding it and it shouldn't be.

I hope the foreman helps you better tomorrow.

Customer: replied 7 years ago.

Well, picked up vehicle, they could not determine the cause and stated a engine mount and something else causing the vibration, they felt still not enough info to determine it is a PCM issue. I did not speak to the service tech or foreman as they were out on lunch. May give them a call. I do not believe they spent much time on this.


I am going to take it to another Ford dealership next week.


Very frustrating.

Another Ford dealer sounds like a better idea. Try to take it to a big dealer, not a little one. You'll probably have better luck.

I'm sorry its frustrating, sounds like your dealing with some not to smart individuals.

Customer: replied 7 years ago.

Hi Juan,


Hope you had a nice Holiday.


I am taking truck over to Gwinnett Place Ford in Duluth today.


I have been speaking with the service manager about the vehicle.


Lets see what hapens.

I had a great holiday, thank you.

Hope yours was well.

Speaking with the manager is great, it might help the technicians look into the problem a little harder.
I am hoping for the best!
Customer: replied 7 years ago.

Hey Juan,


Wanted to provide you an update.


Johnson Jackson is the service manager at Gwinnett Place Ford, just in case he calls you, but I do not hink he will. Spoke to him a couple of times. He is ordering a PCM. Will probably be installed early next week. So, I picked up vehicle until they have the PCM.


He made a couple of comments and felt it may not resolved the issue, but he is willing to give it a try. He said he would carefully unwrap the PCM and install it, worst case he would send it back.


So, my question is, if this does not fix the issue, any thoughts where I go from here? Sell it? Junk yard? :)



Well I'm glad to see that the part is getting ordered, but it still kind of sounds fishy because once you open the box for the pcm it is unable to be returned. You might want to watch the new one get put in, or even see both of them together, just in case.

As for if it doesn't fix it, lets just see what happens with the new pcm first.

Customer: replied 7 years ago.

Probably a good idea, not sure I will have time next week to do this.


Can I mark the PCM or do something to ensure the old was removed? Maybe mark a cable or screw/nut with paint or chalk to ensure they removed it?

I guess you could but I am not sure where, i showed you where the pcm is, behind the battery, If you can think of something to do there, than try it. It can't hurt.
Customer: replied 7 years ago.

Hey Juan,


Hope you had a nice New Years.


Ford called and the PCM has arrived. Will be dropping off vehicle to have them install it. Unfortunately, I do not have the time to spend with them.


Hope this fixes the issue.

I had a good new years, I hope yours was well.

As for your truck, I got my fingers crossed! lol

Customer: replied 7 years ago.

Here is the latest. Dropped off vehicle last night just before they closed.


They called me the morning, said they installed new PCM and it is all fixed. Will pick it up this evening and let you know.


Sounds too good to be true.



lol, i hope so. Please keep me posted

Customer: replied 7 years ago.

Hey Juan,


Looks like it is all fixed.


Would like to send you a copy of the invoice and see what you think.


One items states:



Does the above statement indicate a fuel injector problem? Not really sure how to read the invoice.



Customer: replied 7 years ago.

Here is what I copied from the invoice.



97241 WF

(12A650/12B565) - L
97241 WF

97241 WF

97241 WF

97241 WF

97241 WF

FC: E29 42
PART#: 2L3Z*12A650*ADC


97241 WF

Im glad that its fixed. All the stuff they wrote on the invoice are just tests that were performed. It doesn't mean there was a problem with the injection system. It just means they tested the system. Under warranty, the more tests you do the more you get paid. So it is very common to see all those tests, when you have a warranty repair.
Im glad its fixed, I knew it would be!


Edited by JuanS on 1/9/2010 at 3:08 AM EST
Customer: replied 7 years ago.

Well, I guess I am done with this project for now.


I want to thank you again for all your help and sticking with me on this one.


How can I post a recommendation for you?


Give me a shout if you are ever in the Atlanta area.



No problem,

If you want to leave feedback for me you can, I'd appreciate it.

If i'm ever in Atlanta i will let you know!

Customer: replied 7 years ago.

Hi Juan,


It has been a week, and have 250 miles since the new PCM has been installed. The issued has surfaced again as of last night.