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david craig
david craig, Auto Mechanic
Category: Volvo
Satisfied Customers: 901
Experience:  owner/mechanic at 3D Automotive
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Very strange.... it has erratic and dangerous idle

Customer Question

very strange.... it has erratic and dangerous idle situation. Stopped at a stop sign, foot on the brake and the idle jumps from 800 to 1500, but the car lurches forward.
JA: How many miles are on the car? What size is the engine?
Customer: 187,000, 2001, s40 with 1.9 turbo
JA: What year is your Turbo?
Customer: 2001
JA: Are you fixing your Turbo yourself? What have you tried so far?
Customer: I removed the fuel pressure regulator and found that the screen was damaged, so I bought a new regulator. I got a junk yard idle air control valve. I was able to mechanically test my valve and the JY one. Both seemed to do the same thing. several months back I cleaned the MAF and TB. I fugured I would do that again today.
JA: Anything else you want the mechanic to know before I connect you?
Customer: erratic idle that lurches the car forward. It also happens when coasting down a hill... the acceleration is fast enough for the tranz to change gears.
Submitted: 2 months ago.
Category: Volvo
Expert:  david craig replied 2 months ago.

Hi Im David, thanks for visiting the site. please allow me to look some information up on your vehicle. thanks

Expert:  david craig replied 2 months ago.

It appears to me to be an issue with the throttle position sensor or the accelerator pedal position sensor. to test the throttle position sensor, connect an volt meter to the sensors connector and manually operation the throttle plate. closed voltage should read around .4-.5 vdc and smoothly increase to 4.5-5.0vdc as you manually open the throttle plate.

Customer: replied 2 months ago.
Ok, I am having trouble disconnecting the TB sensor. But once I do, what position is the key in?
Expert:  david craig replied 2 months ago.

you can leave the key off for now

Customer: replied 2 months ago.
had to take the TB off to see how the connector attached. there are 3 connections.... which do I check....
Expert:  david craig replied 2 months ago.

the one on the right

Customer: replied 2 months ago.
Ok. I am checking the TB connections. Not the wire?
Customer: replied 2 months ago.
Red Voltmeter wire on the right male connection. Black VM to ground?
Expert:  david craig replied 2 months ago.

not the wire. how many pins are on the sensor?

Customer: replied 2 months ago.
How do i get voltage with the connector dis connected
Customer: replied 2 months ago.
3
Expert:  david craig replied 2 months ago.

i wanted you to disconnect the sensor to see if it was corroded inside. sorry i should have explained that. with the connector installed you need to back probe with the meter

Customer: replied 2 months ago.
Makes sense now. I'll work on that. I see no corrosion.
Customer: replied 2 months ago.
3 wires. Red, brown and green. Which ones?
Expert:  david craig replied 2 months ago.

standby please. let me get you a print

Expert:  david craig replied 2 months ago.

heres a video. a lot easier than explaining.

https://youtu.be/m_6dhZzWM54

Customer: replied 2 months ago.
Using my phone invthe driveway. Kinda tuff to waych a vid. Just need to know th 2 wire colors.
Expert:  david craig replied 2 months ago.

the 2 end wires

Customer: replied 2 months ago.
Ok. Key still off?
Expert:  david craig replied 2 months ago.

yes

Customer: replied 2 months ago.
1st try i got .04v closed(idle). Open the throttle and it went to 0v. Get no readings now. Re checked continuity but still get 0v
Expert:  david craig replied 2 months ago.

make sure you have the probes in far enough

Customer: replied 2 months ago.
I got continuity from the probe to the connector. Using the same back probe method, Should i get voltage on the center wire? Cause i don't.
Expert:  david craig replied 2 months ago.

no. thats the input from the ecm

Expert:  david craig replied 2 months ago.

you might get it with the key on

Customer: replied 2 months ago.
OK
Customer: replied 2 months ago.
5v with key on. Center wire
Expert:  david craig replied 2 months ago.

thats good

Customer: replied 2 months ago.
5v on other probes with key on and TB closed.
Customer: replied 2 months ago.
Up to 5v wot.
Expert:  david craig replied 2 months ago.

ok then my bad. the key should have been on. sorry bout that

Expert:  david craig replied 2 months ago.

so the tps is good.

Customer: replied 2 months ago.
the key needs to be on.
Expert:  david craig replied 2 months ago.

it was the resistance check that the key was to be off

Customer: replied 2 months ago.
My thoughts too.
Expert:  david craig replied 2 months ago.

but thats not necessary since the voltage is good

Expert:  david craig replied 2 months ago.

do a wiggle test with the meter still hooked up.

Expert:  david craig replied 2 months ago.

see if vibration affects the reading

Customer: replied 2 months ago.
wigggle what?
Expert:  david craig replied 2 months ago.

the wiring harness that the sensors connector is in.

Customer: replied 2 months ago.
It did. But could that be my probe cpnnections?
Expert:  david craig replied 2 months ago.

sure could be. another way to check would be to start the vehicle and shake the harness. see if it affects the rpms

Customer: replied 2 months ago.
I do get some drop.
Customer: replied 2 months ago.
I can't reach the connector with everything attached.
Expert:  david craig replied 2 months ago.

do you have a scan tool?

Customer: replied 2 months ago.
Just grabbing the connector and wiggling gives no drop.
Customer: replied 2 months ago.
OBD? Yes
Expert:  david craig replied 2 months ago.

ok. wiring is probably ok

Expert:  david craig replied 2 months ago.

yes obd. does it read live data?

Customer: replied 2 months ago.
No just codes.
Expert:  david craig replied 2 months ago.

and the check engine light is not on correct?

Customer: replied 2 months ago.
Correct. I'll put it all back together and see if anything is pending.
Expert:  david craig replied 2 months ago.

ok. and i will pull a a test for the accelerator pedal position sensor if i can find one in my books

Customer: replied 2 months ago.
No codes, none pending.
Expert:  david craig replied 2 months ago.

ok the best way to test the accelerator pedal position sensor is to start the vehicle. let it get to operating temp. then slowly and steadily accelerate at from idle to 3000 rpms. the rpms should go up smoothly with out any dead spots or rapid rpm changes

Customer: replied 2 months ago.
Ok
Customer: replied 2 months ago.
5 or 6 tries. Most were smooth. 1 the rpm took off by itself to 4500. Now i am siting here typing and it dis it again.
Expert:  david craig replied 2 months ago.

replace the pedal position sensor.

Customer: replied 2 months ago.
again. Up to 4000. Hold for a sec then down to 800 and holds.
Customer: replied 2 months ago.
where is that?
Expert:  david craig replied 2 months ago.

it is attaches to the gas pedal assembly on top of it

Expert:  david craig replied 2 months ago.

i believe its all one piece

Customer: replied 2 months ago.
Ok. How do i keep you in the loop? I assume this is something i'll have to get on line. I can try a jy one.
Customer: replied 2 months ago.
Looks easy enough.
Expert:  david craig replied 2 months ago.

you can accept the answer, leave a 5 star rating and i will keep this open until we get her fixed.

Customer: replied 2 months ago.
Mine looks different. There is a rod connecting the pedal to the hinge. Pedal forward pushes down on a vacuum can. 2001 S40 b
Expert:  david craig replied 2 months ago.

ok, yea i saw that one too. let me pull something up

Customer: replied 2 months ago.
Not aure about the vacuum can. Does not seem to touch it. Hose on top, hose on bottom. It is just mounted on the same bracket as the pedal.
Expert:  david craig replied 2 months ago.

yea, the pic i sent is the only thing i can find

Customer: replied 2 months ago.
Do i have a pedal position sendor?
Expert:  david craig replied 2 months ago.

can you take a pic of the pedal assembly area

Expert:  david craig replied 2 months ago.

according to my manual you do...sorry the pic is so small

Customer: replied 2 months ago.
Found one on ebay.
Expert:  david craig replied 2 months ago.

there you go. good find

Expert:  david craig replied 2 months ago.

im confident that with that erratic behavior, especially while you were testing it, that will take care of your issue.

Customer: replied 2 months ago.
The whole thing? I just dont see a sensor. I can't read the part # in the picture.
Expert:  david craig replied 2 months ago.

i have to do some more research

Customer: replied 2 months ago.
Thanks for your help.
Expert:  david craig replied 2 months ago.

sorry, had to run out for a few, let me get the coffee started......

Customer: replied 2 months ago.
No rush. Had another car to fix. Beer and football is on the list for the night. Let me know the next thoughts and i'll be on it.…tomorrow ��
Expert:  david craig replied 2 months ago.

ok brother

Customer: replied 2 months ago.
I'll have some time to fiddle with the S40 after 4pm today. Did you come up with any more thoughts. I searched the internet for a 2001 Accelerator Pedal Position sensor and don't seem to find one. Do you have a part #?
Expert:  david craig replied 2 months ago.

im going to call the local volvo dealer

Expert:  david craig replied 2 months ago.

last 8 of you vin?

Customer: replied 2 months ago.
great. I thought I would drive the car to dinner Saturday. WOW>>> it used to rev to 1500 at a stop sign, now the 4000 rev is much more frequent. I turned around and changed cars. Not driving that one 'til we can calm it down a bit. This is my daughters car, she is surely not driving it.
Customer: replied 2 months ago.
4176 is the last 4. I have the whole thing if you need it.
Expert:  david craig replied 2 months ago.

the last 8

Customer: replied 2 months ago.
1F714176
Expert:  david craig replied 2 months ago.

let me have the whole thing...sorry

Expert:  david craig replied 2 months ago.

you dont have one on the vehicle.

Expert:  david craig replied 2 months ago.

it only work by the throttle cable which connects to the throttle linkage on the side of the throttle body. so i have to suspect the tps is bad/intermittent

Customer: replied 2 months ago.
If you still need it.TV1VS9501F714176
Customer: replied 2 months ago.
The yard that i got the IAC from has a TB. I'll see if he will trade. I think it is from a 2000. I'll look for a new one too.
Customer: replied 2 months ago.
Question for you...
1. the TB valve is mechanical and operated by my foot
2. Fuel injection cars are controlled with AIR intake. More air mixes with more fuel and the engine revs, right?
??? So how is more air randomly getting into the intake to rev my car to 4000 rpm? The TB plate is not opening. Even if the computer thought it was open there would not be more air.
Expert:  david craig replied 2 months ago.

vacuum leak

Expert:  david craig replied 2 months ago.

unmetered air entering the engine after the maf sensor

Customer: replied 2 months ago.
A new (different) TB would not solve a vacuum leak tho. the current TB gasket is new and whole.
Expert:  david craig replied 2 months ago.

you can have a vacuum leak anywhere. intake manifold base, ant vacuum hose, brake booster, etc....

Expert:  david craig replied 2 months ago.

get a can of throttle body cleaner and spray all around the engine at any all all sources of vavcuum. if the rpms rev. you have found a leak. but im putting my money on tps

Customer: replied 2 months ago.
i'll get the JY one on the way home. The guy is very nice and will refund my $ if it does not solve my issue. I have the IAC valve to return to him any way.... but I forgot to bring it today. I have tried the carb spray all around the TB, intake, MAF etc... I have never found a vacuum leak on any car.... I hate vacuum leaks. I may as well try it again tho.
Expert:  david craig replied 2 months ago.

ok my friend. keep me posted

Customer: replied 2 months ago.
I got the TB. Gonna need some cleaning. JY dude did not want me to remove the sensor but i might anyway. The thing is a mess.
Expert:  david craig replied 2 months ago.

do it

Customer: replied 2 months ago.
Totally worse now 5 minute test drive was good. At 6th minute crap hit the fan. High revs all the time. I made it home but now it won't start.
Expert:  david craig replied 2 months ago.

what codes you have?

Customer: replied 2 months ago.
No cel
Expert:  david craig replied 2 months ago.

what? ok. can you monitor live data?

Customer: replied 2 months ago.
No check engine light. Only have obd reader.
Expert:  david craig replied 2 months ago.

ok. let me go back over our notes..ill get back with ya

Customer: replied 2 months ago.
I may have found it. The brake booster has a hard plastic pipe that inserts between the TB and the intake. The end of the pipe has a smooth brass nipple that inserts into a wedge type fastener. That connection was wobbly and slid up and down easily. I was able to get it out. Inside the wedge connector is or was an o-ring. Mine is brittle and broken. I suppose as the engine warms up the metal expands and reveals the leak.Looking for an oring to try this afternoon.
Expert:  david craig replied 2 months ago.

nice find and will definitely cause a vac leak

Customer: replied 2 months ago.
I am trying to find a drawing of that area. I can find the hose, but it does not come with the press-to-lock connector or the O-ring.
Since my O-ring broke into pieces, I am not sure what the size specs are.Do you suppose a regular O-ring will be fine to use? I found several at work we use for hydraulics. Orielly's has O-rings for oil and a pack of O-rings made from Viton for gas. This area is near the fuel intake, but it is really only hot air near this O-ring.
Expert:  david craig replied 2 months ago.

if you want to be sure its not going to leak i suggest the dealer parts

Customer: replied 2 months ago.
the damn dealer does not answer the phone. they only communicate with customers at the desk, or online. I emailed them, but who knows how long or if they will ever reply.
Customer: replied 2 months ago.
I have to return these JY parts, so I think I will see if my Junk Yard guy will let me back in the yard. If for nothing else, I can get the press-to-lock and maybe a complete o-ring, but it will probably be brittle too.
Expert:  david craig replied 2 months ago.

how far away is it? drive on down there. walk into the parts department and tell the knucklehead what part you need. dont but jy...especially that

Customer: replied 2 months ago.
I was just thinking the JY for size. There are 2 dealers in town, one is 30 minutes away. They are the pricks. then there is Darrel Waltrip 45 to 50 minutes away. If I have found the right parts online, it won't be $13 for the connector and the o-ring. Just hate to drive that far and them not have it.I am gonna try to use these tonight. Get a good test drive in, maybe drive the car to work tomorrow (fingers crossed), then deal with the correct part.
Expert:  david craig replied 2 months ago.

okey dokey

Customer: replied 2 months ago.
Hey, I got an email reply. I asked him to lookup this part #(###) ###-#### and tell me if there is an oring inside the piece on the left. piece on the right is labeled a plug. I don't want to plug it.http://www.tascaparts.com/oe-volvo/9146615
Expert:  david craig replied 2 months ago.

so what are you gonna do?

Customer: replied 2 months ago.
Bout to go on a test drive.
Expert:  david craig replied 2 months ago.

HOPE ITS A GOOD ONE

Customer: replied 2 months ago.
I thought it was. Got greedy after10 minutes. Then it started over revving again. And like yesterday the car won't start. Guess it flooded when i shut down at 4500 rpm.
Customer: replied 2 months ago.
Problem is now. I am not to close to home.
Expert:  david craig replied 2 months ago.

dude that tps has got to be bad!!!!!!! that or the damn cables ae sticking or the bracket for the throttle cable is on wrong

Expert:  david craig replied 2 months ago.

hows it going?

Customer: replied 2 months ago.
I finally gave up. I found an independent shop that says they specialize in Volvo. The owner was a dealer mechanic. I figured they would have the diagnostic equipment to pin-point my problem. The place is 20 miles from my house, so I was leary about being able to make it. But I babied the car all the way there. When I pulled in and parked the revs hit 3000 and would not stop. I turned it off and put the key in the drop box.They called and told me the following, what do you think?: During their test drive the battery died and would not charge via the ALT, or with a charger. They took the battery out of the car and the charger charged the battery. Then they put the battery back and got wild voltage #s throughout the system.1. they determined that the ALT was shot (under warranty, so that part will be covered)
2. they tell me the + batt cable goes thru or under the intake manifold and has a short in it.
3. Intake mani. has to come off to get the cable out and will need a new gasket.I am having trouble believing that the +batt cable could be causing this, but I suppose with all the sensors and computers in cars these days it could be the problem.How would the car REV assuming there are no vacuum leaks and the Throttle valve is not opening? How is it able to rev? wouldn't MORE AIR have to be introduced to make it rev?Dumb founded.....
Expert:  david craig replied 2 months ago.

unless the cable being shorted causing all the sensors to go nuts..............

Customer: replied 2 months ago.
I asked them to show me the cable when they pull it.
Expert:  david craig replied 2 months ago.

unless they purposely damage it.