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Discussion Starter · #1 ·
My e36 m3 3.0 is idling around 600rpm and is really rough. And when driving and low revs feels as though there is no power up to 3000revs but after that is fine. When you put your foot down in low revs it feels as if there is something holding it back but then when you reach 3k it just seems to be let lose and is fine?it does this when cold and when oil tempeture is up to temp!Any ideas much appreciated!
 

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sounds very much like either a problem with idle control valve, which is under the plenum and difficult to get to, they often have build up of carbon, spray with carby cleaner, also hoses tend to be split on them by this age.

other thing it could be is sticky vanos, or faulty throttle position sensor
 

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Firstly check for air leaks. Once all these have been checked out then it may be worth checking the coil packs.

Does it do it from cold? Does it do it all the time?
 

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sounds very much like either a problem with idle control valve, which is under the plenum and difficult to get to, they often have build up of carbon, spray with carby cleaner, also hoses tend to be split on them by this age.

other thing it could be is sticky vanos, or faulty throttle position sensor
I can get you a picture of the ICV as I have my inlet manifold off at the moment:thumbsup
 

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Discussion Starter · #5 ·
coil packs were changed 5 months ago. Its not a costant problem,it gets better and worse depending on how the car is feeling!lol Cant be an air leak if its fine when you boot it and its over 3k revs. Could it be a sensor problem?i know both cam sensors and the tdc sensor were changed 6 months ago. Could it be crank sensor?
 

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coil packs were changed 5 months ago. Its not a costant problem,it gets better and worse depending on how the car is feeling!lol Cant be an air leak if its fine when you boot it and its over 3k revs. Could it be a sensor problem?i know both cam sensors and the tdc sensor were changed 6 months ago. Could it be crank sensor?
In future please include all relevant information in your posts as we will offer advice on the information given. Also, just because parts have been replaced doesn't mean they can be instantly be ruled out:thumbsup

I see morerevsm3 has beaten me to the picture:rofl
 

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Have you found a solution to your problem? I have a similar problem with my 1995 3.0l M3.

I've changed cam sensors, swapped the ecu, cleaned the ICV, cleaned the MAF, checked for leaks by inspection and with a smoke test. Checked voltage to ecu and all voltages were ~ 13V except for the imobiliser voltage wich was between 8-10V but I'm not sure if this is normal or not.

I've tested every single wire going to sensors for continuity however this was while stopped with a cool engine and the engines characteristics do change quite regularly with this problem.

It also holds the revs up around 1.5K till the car is completely stopped and the TPS is not being depressed then the idle steps down to normal. It does this inbetween gear changes aswell (as the car is still moving even though the TPS is not depressed) which makes it hard to select gears.
 

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mine is lumpy when cold and even more so come close to service time, its fine when warm tho. I have just started to notice its holding back slightly at lower revs but I am putting this down to the service needing
 

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It also holds the revs up around 1.5K till the car is completely stopped and the TPS is not being depressed then the idle steps down to normal. It does this inbetween gear changes aswell (as the car is still moving even though the TPS is not depressed) which makes it hard to select gears.
All M3's do idle at 1500 rpm until a very short time after coming to a complete halt:thumbsup


mine is lumpy when cold and even more so come close to service time, its fine when warm tho. I have just started to notice its holding back slightly at lower revs but I am putting this down to the service needing
When mine is cold, if I boot it too early then it runs like a bag of **** for 5 mins but then clears itself. Think this may be O2 sensor related? If I let it warm up correctly then I don't experience this problem, even if I drive it like a complete lunatic (not that I do just saying, if I did:shifty::rofl)
 

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When mine is cold, if I boot it too early then it runs like a bag of **** for 5 mins but then clears itself. Think this may be O2 sensor related? If I let it warm up correctly then I don't experience this problem, even if I drive it like a complete lunatic (not that I do just saying, if I did:shifty::rofl)
The O2 sensor isn't used on warm up, only the engine temp sensor and the maf, when cold the O2 sensor is in OPEN LOOP, when warmed fully up it goes into CLOSED LOOP and starts taking readings from the 02 sensor.

Also you may like to know that the O2 sensor isn't used on full throttle either, just idle and part throttle, NOT WOT(Wide Open Throttle) :thumbsup

Also the Throttle position sensor is a service item on these cars IIRC, I seem to remember someone saying they are common for going bad.
 

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I will get him to have a drive and tell me what he thinks, cant be anything wrong with it as he test drives it everytime and is not shy to give it the beans
 

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One thing that always gets over looked on the 3 litre M3 are the 6 rubber vacuum caps that sit on the bodies.

They perish over time and leak. This can cause all kinds of problems. New ones are about 50p each
 

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Does the TPS need to be calibrated or something when you put a new one in? I changed mine some time ago and just took the old one off and put new one in and the idle has gone lower since then.
 

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One of my mate's M3s did this, and he said he did not feel the Vanos kick in.

While we were puzzling it my dad put his thumb on the Vanos wire and it ran fine.....
 

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get it checked out quick! Mine was behaving like that after I had a full service on it, 500 miles later and the same symptons as yourself I crawled off the car park at work and theres a horrible metalic grating sound and the car switches off completely - told 74k miles the engines seized. When you've got a 2.8l a corse shouldn't out accerlate you until you get to 3k rvp
 
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