How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask CarQuestionGuy Your Own Question
CarQuestionGuy, Technician
Category: Car
Satisfied Customers: 1259
Experience:  ASE Master Auto Technician for 5 years, ASE Refrigerant Handler, ASA, iATN
Type Your Car Question Here...
CarQuestionGuy is online now
A new question is answered every 9 seconds

91 Hyundai Excel: 000 miles..a level rpm, it misses..cap..timing

This answer was rated:

I have a 91 Hyundai Excel that i recently aquired, this has 171,000 miles on it. The engine reves fine, but once it reaches a level rpm, it misses. When i first got it, the distributer cap eas missing the center pin and I found that the timing was off about 30 degrees. I since replaced the cap, rotor button, wires, plugs, done a spark gap test and the spark will jump a 1-1/2" gap, so thats good. also done a compression check and all cylinders were giving about 180lb of compression. I laso changed the fuel pressure regulator thinking it might be getting too much fuel, since the plugs were wet. seems to have solved the wet plugs, but not the miss. I find this one strange since when you accelerate or decelerate going down the road, it has no mis, but as soon as the rpms are stedy, it will miss. Since it has a 4 speed manual tranny, believe me, you can feel everything. Everytime it misses, you feel the car jurk. Please help, I am out of options.
Thanks for using Just Answer

The most likely cause of your problem in my opinion is probably an EGR related fault. The EGR valve opens when the car is at steady rpms but is closed when it is accelerating. There are many other things that might cause this type of problem (vacuum leak, etc.) but this would be my guess as to the most probable cause.
Customer: replied 8 years ago.
I checked the vacuum and got a reading of about 25 lbs and as i reved the motor, the vacuum actually went down a little. The EGR is moving freely, but no change to the moter when i push it open. The part is expensive and wont get here for a week, Is there any other cause or do you think that this is deffinately the problem? I sprayed ether around the mating servaces of the intake and throttle body, and the engine didn't pickup. I also checked for other vacuum leaks and couldn't find any.
OK well since the motor does not change with the egr valve open it is unlikely (but still possible) that it is the problem.

The next thing to do is get an inline spark tester. The make one that you hook between your spark plug and wire and it stick onto the windshield. Then test drive it and see which, if any, of the cylinders lose spark.
Customer: replied 8 years ago.

Is there a way to completely take the egr out of line and plug it off to see if its the problem? I dont know if this is feesable or not


Whenever I have to do that I take the valve off and make a plug out of like an old oil bottle and install it between the EGR mount and the valve. Then I bolt the valve back up and test drive it. It is better if you can use something other than plastic since it will melt if it gets really hot, but if not then just don't drive it for too long.
I don't know what your valve looks like right off hand, but on most cars this method will work.
Customer: replied 8 years ago.
I am going to attempt to bypass the egr valve tomorrow and see if the motor sounds any better. as to checking the spark, I done a spark gap test on all cylinders, Its firing fine. Im at a total loss on this one. I unplugged the vacuum line to the egr and plugged it off, but no change. If plugging off the egr doesn't work, what should i try next?
You should try the spark test that I told you about. You ignition system might not be working well under the load of the engine. Another thing to test is your fuel pressure while driving. You should get a fuel tester that has a long enough hose to tape onto the windshield when you test drive it, then just watch to see if it drops below what it should be.
Customer: replied 8 years ago.

I performed the spark test you described on all 4 cylinders and for the most part, the spark is blue. Occasionally though I will get yellow/orange spark. This is true on all 4 cylinders. Could this be what is doing it?


I cannot do a fuel test because there is no test port on the fuel system. I cannot seem to find the fitting that is required for this test. I suspect that if the fuel was at falt that the motor would not rev like it does. It has a great deal of power, but it misses.


Also I have noticed that the voltage going to the coil is over 12 volts. Its more like 13.5 or so volts, I dont know if this means anything or not, but i thought I would mention it anyway.

Customer: replied 8 years ago.
Also I failed to mention that i put a piece of aluminum can between the egr valve and intake and completely sealed it off, no change though. So that is ruled out.
The spark should be fine as long as it is sparking. We will assume that all the cylinders are getting the spark that they need.

To do a fuel pressure test if there is no test port you will have to tee into the system. Any good test kit will have the necessary adapters.

The coil should have battery voltage. If there was good spark then that will rule out the coil.

The next thing after the fuel pressure test is to start checking fuel injectors. The only good way to check them is to hook them up to a "scope". They are very expensive so you might need to take it to a repair shop for this test. It will basically show the waveform that the injectors are putting out which will show the condition of the coils inside the injectors.
Customer: replied 8 years ago.
would that cause the plugs to be sooty black? I forgot to mention that.
It could. If there is a leaky fuel injector it could cause the plugs to be wet and/or black from over fueling.
Be sure to check your air filter. If it is starving for air it can cause this too.
Customer: replied 8 years ago.

Well, fuel pressure will need to wait untill i can ubtain the parts to test it, but I am cureous, could i pull the fuel rail and let the injectors spray and tell if they are functioning correctly? Another thought is replacing them one at a time with a new one to see it thats the problem. These are only $32.00 a piece, so I could buy one and try it. or could i pull an injector from something elce and try it? I dont know if they are universal or not.


I was also wondering, what is the purpose of the power transister? If this isnt working properly could that cause the problem?

You might be able to pull the fuel rail and let them spray. This might tell you if any of them are leaking. There are other ways to do this, but you will probably not have the tools for it so that might work. It might be worth a try.
I do not recommend it as far a safety goes, but it might give you the answer you are looking for.
They are most likely not universal but you might be able to find a match laying around somewhere.

Can you tell me more about this power transistor?
Customer: replied 8 years ago.
ok, I pulled the fuel rail and the injectors look like they are spraying pretty good. they do not leak either. I was actually supprised because they all looked cleen on the tips and it looks like the fuel is atomizing fairly well. I guess i can ruel out the injectors.
The next thing then would be to check the fuel pressure while driving.
Customer: replied 8 years ago.

Im sorry, your probably really getting tired of me and this problem. I really appreciate you trying to help me on this. I will be sure I give you a tip on top of the $15.00 to make this worth your while.


Can I Tee into the fuel system on this? Also, is the return line supposed to be pressurized? I know there is pressure there on the supply side, because the hose stifens up a bit, I didnt think that the return line would be pressurized also.


Please advise on this befor i go any further. Thank you

Customer: replied 8 years ago.
I also wanted to ask, when I take the oil cap off, I can feel pulses of air comming out the fill hole, Is this normal? I really havnt noticed if any other motord done this or not.
It's no problem. This is a tough one and I just hope I can help you figure it out. It will be difficult since I can't be where the car is but I can tell you what I would do next if it were here.

Yes you can tee into the fuel system. On some cars that is the only way to test the pressure. The return line will be pressurized. It should not have nearly the amount of pressure that the pressure line has but it will have some.

As far as the pulses yes, this is normal. It is just the air that is moving around inside the engine because of the crankshaft rotating so fast. It's called "positive crankcase ventilation" You've probably heard of that.
Customer: replied 8 years ago.

Ok, I managed to rig up something to connect my fuel guage to and here is what I got.


Key on: Nothing

Start: fluctuates between 38-42lbs

Rev: Pressure increases slightly

regulator without vacuume: 48-50lbs


When I turn the motor off, the pressuer is at about 40 and verry slowly starts to drift off It takes about 20 min to get down to 15lbs.


Its got pressure, what could it be? I thout that the pump was supposed to come on when you turn on the key? Mabe not on this one.

Customer: replied 8 years ago.
Im cureous, What would happen if the timing belt was off one tooth?
If it was off by one tooth it can cause the type of problem that you are describing. That is one of the steps to this diagnosis and if you think it might be off then you should check it.
Customer: replied 8 years ago.

Reason I asked is that I know the timing belt was changed, but I wasn't the one that changed it. It may be possible its not right though. the distributer is ran off the overhead cam on this car.


Here is my threy, If the timing was off one tooth, and the distributer was not moved, this could explane why the timing eas way out before TDC, It wasnt even close to the timing scale. Correct me if im wrong, but I believe that the ignition pulses would be firing too far befor or after the injecton pulses. this may contribute to the black sooty plug and over fueling .


I dont know, its a long shot, but worth a try. I wouldnt think that the moter would have any power if this was the case though


Usually if the timing is off by one tooth the car won't even run or barely run, but on some cars it will run just fine.
This would possible explain why the timing was so far off.
It is definitely worth checking into.
Customer: replied 8 years ago.

I tread the task of getting into that, but at this point, I think we are running out of options. so far, we have ruled out emissions, ignition, fuel , and such. whats left is beond me. I will look into the timing and get back to you on that tomorrow. In the mean time, is there anything elce that I can check?



Sounds good.
You're right...we have ruled out many things. I think at this point the timing is the next best thing to check.
Keep your eyes open for anything else that might be amiss.
Customer: replied 8 years ago.

ok, I checked the timing and it was ok, however, I took my new plugs out to check them and they were wet. also I pulled the egr back off to clean and reattach and when I pulled the slug of stuff out of the bottom hole on the intake, water ran out.


OK, Mabe we are getting someware, How is water getting into the intake? If its trying to atomize with the fuel, that would most certanly make it miss. I took the throttle body off and the whole intake has a oil film on it, but what about the water? if there was a intake gasket leak, that would not make it go through all the cylinders would it? or the same with a head gasket?


What do you reccommend?

Customer: replied 8 years ago.


I changed the head gasket and the intake gaskets and no there is no smoak comming from the exaust anymore, also the plugs are no longer wet either. they are burning good and dry. so it appears that two problems got solved with that one.


Now that i have solved the smoaking and wet plugs, I still need to fgure out the miss.

Regardless of the gasket change, it continues to elude me. Any further suggestions?



You should see what your vacuum readings are. This might help lead us to the problem.
Customer: replied 8 years ago.

my vacuum is good, getting about 20 lb


I checked the computer for fault codes even though there wasn't a check engine light on and i got code 15 which refers to the Motor Position Sensor. Im not sure what they are refering to here, there is nothing on the block like a crank sensor or anything. I dont know if this is in the distributer or what. I do know that there is a hall effect in the distributer that has a metal wheel with cutouts on it, is this what they are referring to?

Please advise.

This is the description of what they are talking about. This could be the source of the problem, but it is not too likely as it would mainly be in use during idle:

The Motor Position Sensor (MPS) is a variable resistor type sensor, installed in the Idle Speed Control (ISC) servo. Its sliding pin is in contact with the plunger end and as the plunger moves, the internal resistance and output voltage of the MPS changes. The MPS senses ISC servo plunger position and sends the signal to the ECU. The ECU controls the valve opening, and consequently the idle speed by using the MPS signal, idle signal, engine coolant temperature signal, load signals (automatic transaxle and air conditioner) and vehicle speed signal.
Customer: replied 8 years ago.

can this be tested? I have called the auto parts store and they cannot seem locate this part. The hayns manual I have doesnt note anything about this sensor either.


How do i test it? I have noticed that when the key is on, but not started, there is a continuous clicking noise from the idal control valve like it cant seem to make up its mind what it wants to do.

  1. Connect an ohmmeter between terminals 1 and 4 of the motor position sensor connector. Terminal 1: Sensor power Terminal 4: Sensor ground
  2. Measure the resistance of the terminals. Standard Value ...4-6 Kohm
  3. Attach an ohmmeter between terminals 2 and 4 of the motor position sensor connector. Terminal 2: MPS output Terminal 4: Sensor ground
  4. Connect a 6V battery between terminals 1 and 2 of the ISC motor connector (to operate the ISC motor) and check to see that resistance of the MPS (step #3 hook-up) changes smoothly when the ISC motor is activated.
  5. If the standard value is not achieved, or if the change is not smooth, replace the ISC servo assembly.


This part is also called an idle switch.
Customer: replied 8 years ago.

ok, the mps ohmed out at 4.21 kohm and the servo range s from .639 - 3.901 Kohm.

the range is smoth, I dont see a problem with this sensor, why would the computer keep this code?


What next?

There could be a problem with the wiring to this switch. It could be a problem between the computer and the switch or another sensor that is causing this problem.
It is possible that there is a problem with one of the other sensors that tell the PCM what to set the idle at that is causing your miss. This is kind of a long shot, but it is possible. The other sensors are:
idle signal, engine coolant temperature signal, load signals (automatic transaxle and air conditioner) and vehicle speed signal.
You might want to check all wiring and connections to these sensors.
Customer: replied 8 years ago.

Well, I checked the wiring, everything is tight on all the sensors. I dont get it, it misses at idle and at any other rpm. its almost as if a plug wire is off one of the cylinders, but we are getting spark to all of the plugs on all of the cylinders!


All the injectors are spraying a nice cone shape pattern of fuel and seem to be atomizing verry nicely. I checked this when the intake was off. I hooked the injectors up and cranked the engin and it looks really good. I dont think it is fuel related because I know it would mess with the idle, but the motor runs really good and has plenty of power other than that damn miss.


I fixed the water leak into the intake when I changed the head gasket and intake gasket. all the plugs are burning dry now and look normal. I dont get it at all. ???



Customer: replied 8 years ago.

Well, I checked the wiring, everything is tight on all the sensors. I dont get it, it misses at idle and at any other rpm. its almost as if a plug wire is off one of the cylinders, but we are getting spark to all of the plugs on all of the cylinders!


All the injectors are spraying a nice cone shape pattern of fuel and seem to be atomizing verry nicely. I checked this when the intake was off. I hooked the injectors up and cranked the engin and it looks really good. I dont think it is fuel related because I know it would mess with the idle, but the motor runs really good and has plenty of power other than that damn miss.


I fixed the water leak into the intake when I changed the head gasket and intake gasket. all the plugs are burning dry now and look normal. I dont get it at all. ???



What was the procedure you used for setting the timing and what was the final timing reading? What is it now?
Customer: replied 8 years ago.

Mechanical timing was easy, there is a timing mark on the grank that as lined up with the refrence on the block and there is a timing mark on the cam that was lined up with the refrence on the head. Belt was put on and tensioner was set and locked down. The crank was turned clockwise 2 times timing marks were realigned and double checked and belt was retensioned. Everything god to go.


Ignition timing is set by placing a jumper from the EST Adjust lead to negative ground of the battery, this disables the timing advance. next, making sure everything is off i.e. ac, blower and such, let it warm up to operating temp and place a timing light on number 1 plug wire which is closest to the belt side of the moter. looking down at the damper, with the light, the notch in the damper is alligned to 5 degrees before TDC by rotating the distributer.


Something to note, when timing is being set, everytime the motor misses, the timing mark jumps back and forth wich makes it dificult to set the timing correctly. I have played with this by retarding the timing and advancing the timing, but it doesnt make much difference, it still misses. Currently it is set at 5 degrees before TopDead Center which is what the lable under the hood says to set it at.



Do you know what the timing is at idle with the check connector reconnected?
Customer: replied 8 years ago.

like I said, even with the check connector to ground, the timing jumps around when it misses, but ir is more or less at 5 degreed befor TDC


What I'm asking is what the timing reading is at idle when the check connector is not connected to ground. I did not word it well in the previous post.
Customer: replied 8 years ago.

ok, I checked the timing and for some reason, the computer is setting timing about 5 degrees after TDC, that's not right. I checked it again with the check connector and it is 5 degrees befor tdc like it should be.


What is going on here?

It should be set at 10 degrees before tdc at idle with the check connector not grounded. So we have to start looking at things that the computer uses to set timing. Mainly the crankshaft sensor and camshaft sensor.
Customer: replied 8 years ago.

This car does not have a crank or cam sensor. I do know that the distributer has a type of hall effect in it, possibly this is what it uses, I don't know. I have looked all over the block for one of these sensors as they are normally either at the damper or the side of the block by the firewall.


Please advise

According to the service manual is has a combination cam/crank sensor. Here is a pic:


No.1 Cylinder TDC Signal :
Top dead center is detected by the signal obtained through the one inner slit of the disc. The ECU, based upon this signal, determines which of the four pulses from crank angle sensor is the signal for the #1 cylinder.
Crankshaft Angle Signal :
The four slits located at the outer circumference of the disc serve to detect the position of the crankshaft (and, therefore, the piston) relative to top dead center. The ECU, based on this signal, determines the fuel injection timing, and also calculates the amount of intake-air, the timing of the ignition signal, etc. for each revolution of the engine.
Customer: replied 8 years ago.

yes, this is what i am referring to as the hall effect, that is what i have been told is the name of it. sorry about that.


How do i determin if it is good or not?


The frist thing is to see if there is anything that looks abnormal. Some of these will crack and this will cause all kinds of problems. Other than that you pretty much have to look at the waveform using a scope to see what kind of waveform it is putting out.
Customer: replied 8 years ago.

So what your implying is that this may be malfunctioning? The disk looks good, however i should mention that the rotor button even though it is fully depressed on the shaft, will move back and forth a little bit, could this be throwing something off? I assumed it was supposed to be this way since the old button was the same way.



It is normal that there is some play in the button.
It is possible that the sensor is not working right. There has to be something that is causing the computer to set the timing incorrectly.
You should also make sure that the distributor shaft does not have any play and that the gears on the bottom of it are good and not worn. This could also cause similar problems.
Customer: replied 8 years ago.

The actual distributer is tight an feels good. there is hardly any play in the actual shaft. in the mean time other than this sensor, is there anything elce to check, as i dont own a scope?



I just noticed that there is a TSB for code 15 that might have something to do with our problem. I have not ruled out the distributor, but we should check this first. Apparently there have been some issues with the grounding on some of the wiring. Here is the TSB Info:

Some 1990 & 1991 Excel and 1991 Scoupe models may experience recurrent activation of the "Check Engine" light and setting of fault code 15 in the engine control module (ECM) memory. The vehicle may exhibit stalling at idle and an inoperative air conditioning compressor when this condition occurs.

These symptoms may be related to a poor throttle position (TP) sensor ground circuit in the ECM wiring harness. The field fix procedure for this condition varies according to the wiring harness manufacturer, but basically involves the soldering of a crimp connection.

The connection involved is located where four black ground wires (five in California specification cars) for the throttle position (TP) sensor, idle speed control (ISC) motor position sensor, volume airflow (VAF) sensor, and engine coolant temperature (ECT) sensor (plus the EGR temperature sensor on California spec. vehicles) are joined with two ground wires leading to the ECM. (See splice SCO8 on page 23-3 of the 1990-1992 Excel Electrical Troubleshooting Manual, or splice SCO3 on page 23-3 of the 1991-1992 Scoupe Electrical Troubleshooting Manual.)




1. Disconnect the battery ground cable.
2. Under the crash pad on the drivers side, disconnect the ECM wiring harness connectors and ground wires from the ECM. Disconnect the two main wiring harness connectors. Remove the tie strap from around the ECM wiring harness and main wiring harness.
3. In the engine compartment, disconnect the A/C low pressure switch connector, A/C compressor bullet connector (blue to red wire), distributor connector, purge control solenoid valve connector, EGR control solenoid valve connector (California spec. vehicles only), pre-excitation resistor connector, and the ground wires leading to the firewall (G07 for Excel, G06 for Scoupe). Remove the three bolts attaching the square ECM wiring loom cover to the intake manifold surge tank. Remove the tie strap holding the EGR/purge control solenoid valve wiring to the accelerator cable.
4. Carefully feed the ECM wiring harness under the crash pad and through the firewall grommet opening into the engine compartment. Pull the harness completely into the engine compartment.
5. The TP Sensor crimp connection splice is located approximately 8 inches from the firewall grommet on the ECM end of the harness.
6. Peel open the wiring harness cover to find the splice. Remove any electrical tape or shrink wrap tubing overthe splice.
7. Solder the crimp connector following the techniques listed under Soldering Techniques.
8. Retape the connection using black electrical tape. Rewrap the wiring bundle with the original cover.
9. Reinstall the wiring harness in its original position. Reattach the square ECM wiring loom cover to the intake manifold surge tank. Reconnect the electrical connectors that were disconnected in steps 2 and 3 and replace the tie straps that were removed. Reconnect the battery ground cable.
10. Verify that ail wiring harnesses are clear of moving parts or hot components.
11. Clean off throttle body carbon deposits per procedure given in fuel system section of the appropriate shop manual. Clean TP sensor connectors at throttle body by disconnecting and spraying with electrical contact cleaner.
12. Using the M.U.T., set the idle speed and TP sensor voltage according to the procedures given in the fuel system section of the appropriate shop manual.


TP Sensor = 480 - 520 mV
MP Sensor = 900 - 1000 mV
Customer: replied 8 years ago.

wow, that might pose a problem. sounds like a chore, Ill get back to you when i have completed this. in the mean time, let me know if you find anything elce.


Bad grounds are bad things.

Sounds good. Let me know what you find.
Customer: replied 8 years ago.

well, that was a job getting that out of there, I didnt find anything wrong with the slices, but i soldered them all anyway. I am going to put everything back together now.


Is there anything elce i should look for while im under the dash?


Not that I know of.
Customer: replied 8 years ago.
got the car back together last night, but no change, still misses.
Since you do not have a scope is there any way you can get ahold of a different distibutor to try. I don't like to just change parts, but since we cannot test it I don't know of any other way.
You could probably find a used one here:
Customer: replied 8 years ago.

I will have to get one.

ok, so to recap, the plugs are all black and sooty looking, but im getting a good spark on all cylinders. Fuel injectors are all good, have a good spray pattern also. Base timing is set at 5 degrees BTDC but when computer takes over, timing changed to 5 degrees ATDC.


if the crank angle sensor is intermittently shorting, which seems to be a problem with these motors as i have found out by serching the net, that would cause my miss and through my timing out of wack.


Could a coolent temp sensor do this also? I have a thought, possibly due to the advanced timing, the plugs are ignighting too late and causing an excessive amount of unburned fuel to be left in the combustion chamber. this in turn is causing my plugs to turn sooty black and foul. Thus causing the miss. Correct?


I will see about getting a distributer. I called all the local junk yards and all these cars that they have seem to be missing the distributers. ??? Sounds like a comon thing going wrong here. Mabe im just amagining it, or i want that to be it anyway. lol

It sounds like you have a good understanding of what MIGHT be causing this problem. It is possible that it is something that we have not thought of but this is the most likely cause of your problem.
The coolant temp sensor could cause similar problems because that is how the computer knows how cold the engine is and might change the timing because of it.
The advanced timing is probably the cause of the deposits on the plugs.

Did you try doing a search on the website I gave you for the part?
Customer: replied 8 years ago.

yes, looks like i can get one for $50.00


I dont know that the lead time will be on the shipping though. Will this forum stay active untill it gets here?


Yes it will. Usually they are very good at getting parts out asap.

Customer: replied 8 years ago.
ill get one on order then
Sounds good. I hope this is what the problem is after all of this! I hate to have you buy a part without knowing for sure that's what it is, but it's the most likely cause of your problem.
Good luck!
Customer: replied 8 years ago.

just cureous, what is the power transister for on this motor?

It basically is similar to an ignitor. The computer tells it when to fire the coil.
Customer: replied 8 years ago.

I got the distributer and installed it as well as a power transister, no change though. The timing seems to have streightened itself out though, it isnt jumping around when I set the base timing anymore. But something elce isnt right.


I have also noticed that the idle control valve just sits there and makes half revolutions back and forth, but doesnt really do anything. This is true when you turn the key on and when the engine is running.


This dont make any sence, what would be next?

What is the timing when you do not have the check connector grounded at idle?
Customer: replied 8 years ago.
about 10 degrees, mabe a little past that like 11 degrees or so.
OK so this is now where it should be. This is good.
This idle control valve seems suspicious simply because if it is letting too much air in when the enigine is running it might cause this type of problem.

I really thought the timing problem would have something to do with the problem, but since it is now working normally we need to think about anything else that could be causing this problem.

Is there any way you can block off the idle control vavle port on this engine?
Customer: replied 8 years ago.

it doesnt work that way, this is an assymbly that has the idel control moter and motor position sensor connected behind the throttle body. the plunger pushes on the throttle to open it.


I have tried unplugging this, no change. the motor just rotates back and forth without actually moving the plunger. I have tested this assymbly per instructions and I do know that it works. If i put a 6volt battery on the motor, it will fully extend the plunger and retract it, but the computer just pulses it back and forth.


the motor control sensor was tested also and it was also good. as the plunger moves back and forth, the resistence changes smothly as it should.


I dont understand why it bounces back and forth like it does, but this is regardless of wether the motor is running or not.

OK Gotcha. The only thing you might do is maybe unbolt it or something so it can't hold the throttle open and drive it to see if it helps any.
After the above test, the next thing we should do is try to isolate this missfire. With the engine idling pull off each spark plug one by one and see which one does not change the engine rpm. When you come to the one that is causing the problem you will notice no difference in how the engine runs with the spark plug cable off.

Let me know what you find.
Customer: replied 8 years ago.

well, i done the test you mentioned, and all the cylinders changed the rpm of the engine.

You could definately hear that there was a plug off.


Another thing, I put brand new plugs in and within 5 minutes, took them out and they are all saturated and black. Its like its getting too much fuel or something.


also, what would make the idle motor act up like it does?


would it be possible that the ecm is going bad?

If this procedure does not show which cylinder has a misfire then it must be something that is in common with all of them.

The ECM is probably not bad, but it is possible. The black soot on the plugs probably indicates that there is probably a fuel issue.

Have you done checkes for a vacuum leak?
Customer: replied 8 years ago.
yes, over and over again. No leaks, i sealed everuthing and checked around the engine with a stethiscope hose. absolutely no hissing sounds anyware.
Have you tried cleaning the airflow meter?
Customer: replied 8 years ago.
I have sprayed it with throttle body cleaner yes, that was one of the first things i did besides change the filter.
Did you remove it and clean it? If not you might want to do that as it gets it a lot cleaner if you get it out of the air duct.
Customer: replied 8 years ago.
yes, I took it out and also cleaned the throttle body and plentum as well
The next thing we need to do is have the emissions analyzed. If it is over fueling or under fueling it can cause your problem. It would help to know which it is doing.
It should not cost too much to have done if you can find a shop that does it.
Customer: replied 8 years ago.
The problem is getting it there, the thing about gives you whip lash when you drive it. I am going to say possibly overfueling due to the wet plugs
I thought you said the plugs were completely dry after you replaced the head gasket? Are they getting really wet again?

One of the other experts here thinks that it could be a computer issue, so the might be something to consider more.
Customer: replied 8 years ago.
yes, didnt notice it untill i changed the plugs out with new ones tonight.
You should also check your motor mounts. This is where this engine grounds. If they are bad it could cause your problem.
Customer: replied 8 years ago.

motor mounts are good, I also tried running a ground to the body from the motor, but no change. I also cleaned all the cables from the body and battery. no change.



So then the next thing would be to see if you could get it in to somewhere that can check emissions.
Customer: replied 8 years ago.

I fixed the car, I got a ECM from the junk yard and the missing went away and the IACV is now working like it should. I took the brain apart and there are several capaciters that are charred.


I am cureous if the guy that had this mabe put the bad distributer cap on and when it started acting up, mabe started prodding around on certain sensors and trickeled some stray voltage into the computer and fried it.


Oh well, its fixed now anyway.

This definitely could have caused it. Computers are very sensitive and any stary voltage or voltage spikes can cause this type of problem.

I'm very glad that it is fixed. The more we went the more I was leaning toward the ECM but since it is very rare for them to go out I wanted to be sure.

CarQuestionGuy and 6 other Car Specialists are ready to help you
Customer: replied 8 years ago.

I want to thank you for all the help that you gave me, I appreciate it verry much.


Thank you

It's no problem. I wish I could have gotten you through the steps faster, but it's fixed and that was the goal. You did well with the diagnostics that I asked you to do...that makes things much easier for me!

Thanks for accepting, the feedback and using Just Answer

Customer: replied 8 years ago.

ok, I have a new problem, and cant seem to figuer this out. Car has been running fine for some time now, but recently It has been trying to flood when attempting to start it in the mornings or when it has been sitting and cools down.


Something is causing it to dump excessive fuel. also it wants to drop the idle down to 500 rpm or so. I have to keep it revved up untill it warms up in order to keep it started. The exaust smells strong like gas also.


I changed the coolent temp sensor, O2 sensor, checked fuel regulator, etc and cant seem to figure out the problem.


When it warms up, it runs fine, except for a little ritch mabe. Pulling the plus after running it, look to be whitish soty looking. replaced plugs.


Any idea what is going on here?

Customer: replied 7 years ago.
found out that it was the ECM again, replaced it, and all was fine for about 2 weeks. It took i out again. that is 3 ECM's. How do I find out what is taking these out?

Since we have talked last, I have aqured a scope. it is a 30Mhz duel trace. FYI.

Please help me.