S54 tech question
Discussion
Hello, owner of a 2006 S54 here, 206000km, slight cold start issue:
As long as the air-plus system is on (first 30-40sec) the engine vibrates somewhat, like a slight misfire.
Once it turns off, its smooth as silk, running normal.
This started about 10000km ago, gradually gotten worse.
Whats this?
Done compression test, leak-down test, cleaned all injectors, new sparkplugs, changed all coils, checked the function of the air-plus valve. Everything is good.
As long as the air-plus system is on (first 30-40sec) the engine vibrates somewhat, like a slight misfire.
Once it turns off, its smooth as silk, running normal.
This started about 10000km ago, gradually gotten worse.
Whats this?
Done compression test, leak-down test, cleaned all injectors, new sparkplugs, changed all coils, checked the function of the air-plus valve. Everything is good.
Edited by Pereldh on Sunday 26th February 19:43
My S54 does it too!
It seems it isn't unusual going by this:- https://forums.m3cutters.co.uk/threads/m3-e46-kang...
But while it seems pretty normal I'm not sure anyone has come up with a cure.
It seems it isn't unusual going by this:- https://forums.m3cutters.co.uk/threads/m3-e46-kang...
But while it seems pretty normal I'm not sure anyone has come up with a cure.
The car runs in open loop fuelling for the cold start sequence. It determines fuelling from the coolant temp sensor I believe. If you sensor is showing incorrect temperature then the car will over or under fuel which could be causing your misfire. Once out of cold start it uses the lambda sensor instead.
You need a diagnostic tool really to run some tests rather than throw parts at it. But from what you’ve said it sounds like the sensor the ECU uses for cold start is getting an inaccurate temp (probably hotter than it really is)
You need a diagnostic tool really to run some tests rather than throw parts at it. But from what you’ve said it sounds like the sensor the ECU uses for cold start is getting an inaccurate temp (probably hotter than it really is)
Mine (in a 2001 M Coupe) has done it forever and I only found out after about 10 years of ownership it’s due to an additional pump (air I think) that’s there to meet emissions or something. Once the car is warmed up it switches off so the car runs fine.
Redish do a delete mod which gets rid of it and the effect your talking about, but tbh I like the old school feel it gives the car.
Redish do a delete mod which gets rid of it and the effect your talking about, but tbh I like the old school feel it gives the car.
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