Car is running poorly at idle

[dude8383]

Morning!

Ok the problem started happening on friday..

I came back home from school and got in my car...ran it for like 2-3 min to let it warm up. This is the usual process when i park my car next to the train station.

Anyways I drive around to find a place to eat...as I'm pulling up to a red light in neutral, my car suddenly idles around 600 rpm. It stays steady at that rpm but sounds like it wants to stall..i checked the wires to make sure none popped out, checked the coil packs and even tried disconnecting the AFM but the same thing was happening.

Where else should i look??

Can it be the AFM? The spark plugs and wires are only like 3 months old...so I'm 100% sure it can't be that.

Oh, and the car runs fine otherwise...just the idle is terrible.


Any suggestions?

Denis

[Alpine003]

IACV

Are you getting any codes?

[dude8383]

i haven't tried the stomp test yet...

while on that, how do i do it? put the key in accessory and then stomp 5 times?

[bmwman91]

Yup. Accessory, stomp 5 times. Wait 2 2 seconds and the CEL will turn out, then back on in about a second. From there it will go out and then blink out the 4 digit code. It will do all stored codes, then go back to lit for 3 seconds, then repeat itself.

If you did not see a CEL turn on at idle there is probably nothing stored in there. It will only store a code if the CEL came on for whatever reason. Good luck! Sounds like the ICV!

[m42 fan]

I'll third the ICV. It's easy to clean it out with TB cleaner anyway, couldn't hurt.

Brian

[dude8383]

Yup. Accessory, stomp 5 times. Wait 2 2 seconds and the CEL will turn out, then back on in about a second. From there it will go out and then blink out the 4 digit code. It will do all stored codes, then go back to lit for 3 seconds, then repeat itself.

If you did not see a CEL turn on at idle there is probably nothing stored in there. It will only store a code if the CEL came on for whatever reason. Good luck! Sounds like the ICV!

yeh CEL was on at idle..

so the ICV can fail that suddenly?! I'll clean it out today..

thanks!

[bmwman91]

What code did the CEL blink out to you?

[dude8383]

What code did the CEL blink out to you?

haven't yet done the stomp test...ill take care of it when i get home, still at work.

ill keep you guys posted.

[dude8383]

ERROR CODE:

1216

Throttle Potentiometer...

I'm going to check fuses and make sure the sensor is clean. If nothing works after that I'm gonna have to order a new TPS sensor..

[doigal]

Try the idle bypass hoses, ICV and the throttle body - all worth investigating!

[Alpine003]

ERROR CODE:

1216

Throttle Potentiometer...

I'm going to check fuses and make sure the sensor is clean. If nothing works after that I'm gonna have to order a new TPS sensor..

Before you go and blow money, at least test the tps sensor with a multimeter. It might just need to be adjusted. I can't recall if the M42 motors come with tamper markings on the TPS screws or not. If it does, you might want to see if it's been messed with before.

[bmwman91]

That is the same code I get. I removed the TPS and disassembled it to see if the carbon track was shot, but all seemed fine, and it operated with no discontinuities. I still get the code every now & thenm and the idle sorta fluctuates...but I attributed that to the MAF.

Try resetting the ECU? If it somehow got adjusted then the ECU needs to re-learn the positions.

[dude8383]

Try the idle bypass hoses, ICV and the throttle body - all worth investigating!

where are the idle bypass hoses?

I checked the ICV and throttle body...

Will answer the whole thing below..

Before you go and blow money, at least test the tps sensor with a multimeter. It might just need to be adjusted. I can't recall if the M42 motors come with tamper markings on the TPS screws or not. If it does, you might want to see if it's been messed with before.

Didn't blow any money on that, i had a spare..

That is the same code I get. I removed the TPS and disassembled it to see if the carbon track was shot, but all seemed fine, and it operated with no discontinuities. I still get the code every now & thenm and the idle sorta fluctuates...but I attributed that to the MAF.

Try resetting the ECU? If it somehow got adjusted then the ECU needs to re-learn the positions.

I tried resetting the ECU..that didn't help


Here's what happened today...

I tried all of the things you guys mentioned.

I switched out the AFM and TPS...that didn't solve anything

This is what my friend and I tried:

Checked the spark plugs and wires...the car was misfiring so we thought that was a possibility..

Removed the AFM and swapped it with one that works...same deal, the car would start and stall almost immediately

We disconnected the AFM and ICV and the car ran BETTER...not great, but much better with both plugged in.

Then we tried plugging them in separately, once with AFM plugged in and ICV disconnected, and then vice versa...same deal.

We're thinking that it MAY be the ECU.. i think that the MarkD chip is sending wayyy too much fuel because the car is running extremely rich at low rpm.

I'm going to try swapping in the stock chip to see if that changes anything.

Otherwise, I'm pretty much out of ideas!

:confused:

What do you guys think?

[dude8383]

took out ECU...going to swap in stock chip when i get home from work.

[dude8383]

everyone stumped huh?

[bmwman91]

Yes sir. Seems the only possibility left is the ECU somehow.

[thumper3ld]

Yo, dont forget i got that spare ecu if you need it. just gimme a call.

[e9nine]

Error codes aren't always the golden indicator. Sometimes you can get false errors.

I have to say that the cold weather always seems to do a slight bit of "damage" to the idle behavior of some cars - ours included.

You seem to have done the basics. ICV - AFM - TPS -

Try clean your Throttle body if you haven't already done so - a key part of idle is the primary throttle body opening up and perhaps some gunk in there is causing some issues. Needless to say - check the vaccum hoses as well.

G.Luck :confused:

[dude8383]

cleaned out the throttle body pretty nicely actually...

im definitly going to look for vacuum leaks.

i need to have this car running by tomorrow!!!!

Thanks for all the help...keep it coming!

[e9nine]

As the car runs poorly - does tugging on the TPS wire and AFM wires make any difference? I once had a broken wire in the sheath that took me a while to figure out.

[dude8383]

hmmm i didn't try that.

ill give it a shot.

im going to swap the chip right now.

[dude8383]

Ok, here's the run down.

We tried disconnecting all of the items above same problem was happening.

I took out the Chilton manual (best one out there for m42's) and located the whole electrical diagram for how the TPS functions.

The manual says:

If either switch (in the TPS) fails, the control unit will use air meter signals to calculate idle and full load control and a fault code will be in memory.

Basically whats happening is:

The TPS is not reading proper ohm's at idle and WOT. It should be reading about .8 -1.2 ohms to 3.2 to 4.8 ohm's. We were getting reads of 1.3 at idle and about 4.9 at WOT.

I have adjusted the idle screw temporarily until i get my new TPS unit.

The wiring harness that connects to the TPS switch reads the correct figures.

Make any sense?

[doigal]

The hoses i was refering to are the ones that bypass the throttle body and go into the ICV - that was the culprit for my idle problems. Some are a little buried under the inlet and hard to see, if ones come loose thats the problem.

[Alpine003]

It should be reading about .8 -1.2 ohms to 3.2 to 4.8 ohm's. We were getting reads of 1.3 at idle and about 4.9 at WOT.

Depending on climate and the quality of your leads on your multimeter, it is easy to get .1-.3 variance in resistance just from the leads. You should take that into account when doing measurements. Just touch your leads together to see what your variance is for the resistance on the leads and subtract that from your readings to get an actual figure.

[dude8383]

Depending on climate and the quality of your leads on your multimeter, it is easy to get .1-.3 variance in resistance just from the leads. You should take that into account when doing measurements. Just touch your leads together to see what your variance is for the resistance on the leads and subtract that from your readings to get an actual figure.

i didn't that into account...ill check it out tonight!

[kowalski]

That is the same code I get. I removed the TPS and disassembled it to see if the carbon track was shot, but all seemed fine, and it operated with no discontinuities. I still get the code every now & thenm and the idle sorta fluctuates...but I attributed that to the MAF.

Try resetting the ECU? If it somehow got adjusted then the ECU needs to re-learn the positions.


i got the same code, bought a new TPS, now i have a spare... turns out it was a broken wire. check wiggle the wires on it and see if it your idle gets crappy.

[RED IS 91]

Ok, here's the run down.

We tried disconnecting all of the items above same problem was happening.

I took out the Chilton manual (best one out there for m42's) and located the whole electrical diagram for how the TPS functions.

The manual says:

If either switch (in the TPS) fails, the control unit will use air meter signals to calculate idle and full load control and a fault code will be in memory.

Basically whats happening is:

The TPS is not reading proper ohm's at idle and WOT. It should be reading about .8 -1.2 ohms to 3.2 to 4.8 ohm's. We were getting reads of 1.3 at idle and about 4.9 at WOT.

I have adjusted the idle screw temporarily until i get my new TPS unit.

The wiring harness that connects to the TPS switch reads the correct figures.

Make any sense?

Here is the procedure for checking the tps according to Bentley's manual .
How do you check ohms while the car is running ?? do you peel back the rubber boot at the tps ?
When done according to bentley the car is not running ..
I don't know which is better . I don't have a Chiltons manual .This might help.
Make sure you have the orientation right .I think the photo is upside down cause #1 terminal is actually on top not bottom.
I just checked my tps and everything was within specs . If I uplug it while it's idleing it will die immediately ...

http://i141.photobucket.com/albums/r73/bogeyman700/tps.jpg

[dude8383]

the car was not on during the tests.

the TPS is supposed to read .8 - 1.2ohm's in the idle position and the same for WOT.

sorry if i made the impression that the car was running.

according to the pic you attached, i did method 3.

im not sure, but i may have tried method 2 as well.

thanks for the info though!

my package with goodies including the new TPS sensor should be waiting for me at home... im just stuck here in school studying for finals...wooppeee!

[RED IS 91]

the car was not on during the tests.

the TPS is supposed to read .8 - 1.2ohm's in the idle position and the same for WOT.

sorry if i made the impression that the car was running.

according to the pic you attached, i did method 3.

im not sure, but i may have tried method 2 as well.

thanks for the info though!

my package with goodies including the new TPS sensor should be waiting for me at home... im just stuck here in school studying for finals...wooppeee!
Those are not methods ,those are the 3 test for your tps.Each one test a different part of the tps .

[dude8383]

interesting...well they look like trouble-shooting instructions to diagnoise the TPS.

i did all of those and found that, the harness itself was reading proper values, and it was in fact the TPS that wasn't.

[RED IS 91]

interesting...well they look like trouble-shooting instructions to diagnoise the TPS.

i did all of those and found that, the harness itself was reading proper values, and it was in fact the TPS that wasn't.

Be careful cause I found terminal one is actually the top one not the bottom as shown in the picture.The picture show the screws for the tps on the right ,
If you look at your tps from the drivers side the screws are on the left.

[dude8383]

oh no, i noticed that as well...it looks like it might be the TPS from the m20, or the pic may be just flipped upside down?

thanks for pointing it out nonetheless..

[kowalski]

check resistance on your crank sensor! takes 2 seconds.