Fluctuating revs when idle

[Daaaaan]

Hey guys

I turn to this community again regarding an issue because it's been very helpful and prompt each time...I've had this problem since i got the car 2 years ago, but never really bothered with it...until the issue started to occur more frequently:

Sometimes, maybe once a day, after i drive the car normally around town and stop at a red light with the car in neutral, the revs drop from 850 rot/min to 400-500 rot/min for a second, the car trembles as you would expect, them they go back up and everything is ok. I've noticed this happening more frequently if i stop on a slope...i think. Although it happens on perfectly level roads also.

On rare occasions, maybe once every 2 weeks, the engine comes to a complete stop, as if you were releasing the clutch without putting the car in neutral.

Anyone else had this annoying problem?

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[Daaaaan]

Pls delete one of the threads, i double posted and cannot delete from phone

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[Ricey01]

Left bollock wagered on the MAF sensor.

 

[Daaaaan]

Left bollock wagered on the MAF sensor.

Could you please explain? I don't understand...

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[Captainken]

Mass Air Flow sensor........I would have thought that the Engine Management light would have come on if this was at fault though?

 

[Swiftly]

Have you checked if there are any error codes stored?

 

[Daaaaan]

Mass Air Flow sensor........I would have thought that the Engine Management light would have come on if this was at fault though?

No lights on i'm afraid...

Have you checked if there are any error codes stored?

I'll try and get a reading done today. Last time BMW checked for errors there was one that said that the Vanos sometimes looses connection (with the ECU i suppose)...don't know if this is related...

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[bradmarsh1989]

This happened to me after not starting my car for over 9 months... it would sit idle blipping up and down between 450-800rpm on in waves... engine light came on and after revving to red line a little bit to clear out the crap in the engine it settled down and no longer does this.

 

[Daaaaan]

This happened to me after not starting my car for over 9 months... it would sit idle blipping up and down between 450-800rpm on in waves... engine light came on and after revving to red line a little bit to clear out the crap in the engine it settled down and no longer does this.

This is not the case for me, unfortunately...i use the car daily and reving it up does not solve the problem. I tried this and also tried using petrol from different stations. I also use only 99 or 100 octanic figures...

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[horseofwar]

Had this issue on my 2.0 a few months back http://www.z4-forum.com/forum/viewtopic.php?f=3&t=64194

Not sure which repair corrected the idle issue but here's the list of work that was carried out;

Timing chain replaced (chain tensioner had failed and chain had slackened, you could hear the chain rattling under the bonnet)
Coil packs (3 out of 4 were out with manufacturer limits. Likely to be your issue I think, someone with more knowledge will confirm)
Cracked manifold (not bad enough to put up error but you could hear that it was blown)

All three repaired and car now no longer does what you are describing.