Idle stumbles when engine returns to idle

[Carl King]

Hi all,

I've got a 1.9ltr manual trans 97 Z3. 134k miles on it. About a month ago the engine would start stumbling for about a split second or so after returning to idle, then return to normal idle. Occasionally it'll do it while just sitting idling. RPMs drop to about 500 then it returns to about 800.

On other cars this might indicate a sluggish EGR valve but I read these cars don't have one.

Back in August I had trouble starting it so disconnected the MAF. It seems to run fine without it and I'll be replacing it soon.

Ideas?

 

[Stevo7682]

When you disconnect the Maf the problem didn't go away .
ECU went into a preset back up to keep the car running this could have now caused further issues running this that way for too long.
First change the Maf sensor check all hoses for air leaks reset fault codes see where you are from there.
Stephen.

 

[the Nefyn cat]

What he said, code reader is the best place to start. And moving to the "Z3 Roadster and Coupe" section will get more people seeing your question.

 

[ktnez99]

I’ve noticed the past few days that my car’s spluttering at start-up and is fluctuating between 5000rpm and 8000rpm very quickly. Then after a few minutes, the engine settles and is at 7000rpm.

Is this due to the cold?

I’m kinda thinking that the exhaust maybe blowing and am planning to take my car to have it checked as I had a half new middle to rear exhaust fitted about a year ago and it’s got a lifetime guarantee.

Any thoughts?

 

[t-tony]

5,000, 8,000 & 7,000. That’s some idle speed Dawn.

Tony.

 

[ktnez99]

5,000, 8,000 & 7,000. That’s some idle speed Dawn.

Tony.

too many zeros, thanks for pointing this out

It’s s serious question!!!

 

[the Nefyn cat]

So long as it settles down once it's warmed up don't worry too much. Probably worth plugging in a code reader just to make sure, but engines don't like being cold. Not the only ones.

 

[ktnez99]

So long as it settles down once it's warmed up don't worry too much. Probably worth plugging in a code reader just to make sure, but engines don't like being cold. Not the only ones.

I have a code reader so I’ll find time this weekend to see what it says.

 

[t-tony]

So long as it idles smoothly once thoroughly warm I wouldn't be too concerned.

Tony.

 

[ktnez99]

So long as it idles smoothly once thoroughly warm I wouldn't be too concerned.

Tony.

It idles smoothly, yes.
Sounds like me today!

 

[colb]

It wouldn't hurt to whip the idle control valve off and give it a clean with a spray of carb cleaner, they can get gummed up and stick, its easy to do it sits at the front of the engine, one connector and two bolts hold it in place. wash it out with the cleaner, allow to dry and refit.
Item No 9 on here https://www.realoem.com/bmw/enUS/showparts?id=CM12-EUR-12-1999-Z3-BMW-Z3_19&diagId=13_1733

 

[Carl King]

It wouldn't hurt to whip the idle control valve off and give it a clean with a spray of carb cleaner, they can get gummed up and stick, its easy to do it sits at the front of the engine, one connector and two bolts hold it in place. wash it out with the cleaner, allow to dry and refit.
Item No 9 on here https://www.realoem.com/bmw/enUS/showparts?id=CM12-EUR-12-1999-Z3-BMW-Z3_19&diagId=13_1733

Sounds good. I'll do that.

Thanks.

 

[Carl King]

What he said, code reader is the best place to start. And moving to the "Z3 Roadster and Coupe" section will get more people seeing your question.

The only code I saw was for the MAF, being disconnected. I shot some cleaner through it and reconnected it. The code went away after a few minutes driving time. I also cleaned the idle control valve with carb cleaner.

We'll see what happens now. I'll drive it for a few days and see if the issue recurs.