Hello everyone! I am writing from Hungary about an R53 facelift version. I have a problem at idle/fast throttle blip and at cold start when the car just suddenly starts to stutter/rpm goes low and after a few seconds clears itself up. There is also a slight vibration on the inside door panel and on the wheel, so the car vibrates, i guess due to the incorrect idle. My rpm is also moves a bit up and down but only so little that someone new to the car wouldnt even notice. I have CHANGED/OR TESTED EVERYTHING on the car EXCEPT THE WIRING AND CATALYTIC CONVERTER. I have also rebuilt the whole engine and cylinder head, the car without the belt runs fine and my compressions is spot on in every cylinder (10 bar each).

So everything is changed (MAP, TMAP, O2 SENSORS, CHECKED FOR VACUUM LEAKS, INJECTORS TESTED, FUEL PUMP, FILET etc., You name it) except the above.

Any help would be greatly appreciated as i have seen a few similar issues here, however no definite solutions. Thanks in advance.

 

do you have inpa ? You can check spefic things so your not throwing money in the dark.. try doing a throttle reset and resetting short and long term fueltrims..
throttle reset can be done without any tools or anything..
if you Google r53 throttle reset procedure you'll see it.
If you DONT hear your throttle blade making a humming noise , a few clicks and then one final click.. then its not correctly lining up and that could be the cause of your issues is your throttle blade angle is off from a failing or faulty throttlebody. But that's just my guess.

 

Thanks, I have tried resetting it and also thrown in a used throttle body....no change. This week i will try a new throttle body as well. I did reset the ECU - also changed it to a new one from a properly working car - no change. Thats what i meant when i said everything is new except the above. Luckily my mechanic can get second hand parts "free to try" so no issues in the money department.... yet :D

 

Sounds like a vacuum leak. Have you smoke tested it?

 

That honestly sounds pretty normal. My car has always had an occasional rough idle and slight changes in idle speed - maybe a delta of 30 rpm or so.

 

Sounds normal to me then too if no cel and its running correctly by butt dyno..
even my wife's 20k 2017 crv the idle fluctuates slightly at idle in park or neutral..it's pretty common on a 4cyl from my experience around engines. Only super smooth idles I see are strait 6s or Mercedes or other high-end cars like a jaguar. So long as it's not fluctuating more than 300rpm I'd think it's fine.

 

The problem is that it vibrates slightly (more than a normal 4 cylinder) and if i give a quick throttle (sounds like a misfire but i do not think it is as there is no code for it) blip the rpm goes under 800 rpm and starts to stutter for a few seconds then the rpm goes up by itself a bit (around 900 rpm) and clears itself out. So it is not normal.

 

It sounds like a vacuum leak.
Also, did you clean your throttle body lately? Mine was quite dirty when I restored my car.

 

Every hose checked, throttle body changed, tomorrow a third one will b tried on it. Was thinking of buying all the vacuum hoses, however my mechanic (thank god for his persistence btw :D ) told me that a few hoses are new and the old ones are tested and everything seems fine. Was thinking of harmonic balancer (however that one also checked and seems fine, but was not removed) or the DMF (brand new LUK, fitted this June).

 

Factory Cam?

 

Yes, factory. My engine and head is rebuilt, camshaft, rocker arms, lifter seems fine. However i forgot to mention that once you unplug both map sensors everything seems fine. Changed both maps sensor too (factory original from bmw), but no change at all.

 

Check the tmap plug for corrosion or breakage. Really common late in life. Could be anything really. I recently had a TB/AP sync issue myself that acted like this but I am not on a stock ecu. When you unplug them you go into open loop so its not taking feedback from any sensors other than AP at that point which could help you arrow down sub system issues.

 

Check the crank position sensor.

 

Thanks! Whats the TB/AP sync? TB i guess is the throttle body but never heard of the AP.

 

Accelerator pedal. drive by wire thing.

 

Replaced it already. I will try to replace the coolant temp sensor... it shows the right temp in live data, however u can never know and it affects air/fuel mixture

 

Ive been wrestling with a rough idle on my R50 for years. I’ve reset the idle, cleaned injectors, replaced all the motor mounts. Loosened and torqued every sub frame bolt.

My compression isn’t as even but my roughness occurs even on deceleration so I don’t think it is compression.

When it is cold, it is particularly bad.

Curiously, once warmed, the idle is 850 w/o A/C and 1050rpm with A/C. I don’t know why it climbs so high.

Also I don’t have every good vacuum and only a few degrees of ignition advance.

Peter