RPM Surging

[oldzilla]

I need some advise, or just maybe piece of mind, I have noticed a few times my RPM surging in the morning, it does not do it a start up, and I do not let it idle to warm up. It happens when I stop at the traffic light, it will go from 700 to 500 and back, and you can feel it stutter like it wants to stall. I have taken it in and had the inspection 2 done, mentioned it to my Indy and he said it was normal etc.

This is my first BMW and honestly I am a bit over protective and may be reading to much into it. It only does it a couple of times and never when the outside temp is above 50.

[Oli77]

I cleaned my ICV a couple of times and that helped a bit. Mine would dip a little low when coming to a stop (manual).

What helped the most so far was a third of a bottle of seafoam in the tank.

How many miles?

[oldzilla]

Coming up to 60k, manual tranny. I have only noticed it in the AM so I am thinking it is normal warm up..

[gmurphy]

Normalish...


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[oldzilla]

Thank you all...

[Torxuvin]

Sounds like it could be a minor vacuum leak to me if anything. Check your rubber intake boots. (between the engine and the intake box) Should be an easy check and inexpensive fix if they do need replacement. Mine were completely shot around 95k miles. Eventually they will get bad enough to throw misfire codes and a check engine light. Either way it's not a big deal.

[NorCalZman]

yeah that is strange. I have never noticed my rpms drop down at a stop past where they are supposed to. They just come down to idle and stay there nice and buttery smooth. I will pay more attention on my road trip to Tahoe this weekend just to be sure.

[stephenkirsh]

That's not normal at all. Mine did this and had the exact same symptoms you have, including only doing it in the morning.

It was from a vacuum leak on my DISA valve.

If you can't find a solution, get a smoke test done. My Indy said it was a pretty obvious leak.

I got a new DISA valve and the problem was solved.

[stephenkirsh]

yeah that is strange. I have never noticed my rpms drop down at a stop past where they are supposed to. They just come down to idle and stay there nice and buttery smooth. I will pay more attention on my road trip to Tahoe this weekend just to be sure.

Exactly. No healthy M54 is bouncing around 200 rpm a idle. That's a variation of 33% (200/600=.3333).

[gmurphy]

Should have read more into this before I posted. Your RPMs will fluctuate but not by that much. Check your MAF, intake boots, and DISA.


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[oldzilla]

Will do all thanks for all the advise and help, will let you all know.

[Fender215]

Do insist on starting with a smoke test vs having them say replace the maf which is pricey


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[Avetiso]

O2 sensors and a DME fixed it for me.

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