Lumpy idle only after hot start

[Phoenix///M3]

Always had this issue but never chased it down or knew where to start. On cold start it cranks, fires and idles smooth. Drive 10 miles, shut it off and refire and the idle jumps 500 rpm up and down for 1-2 minutes then settles down. Repeats on restart until cold again. Plugs, coil packs and TPS underhood all new. If it were the ICV why only when hot for 2 min?


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[sapote]

Always had this issue but never chased it down or knew where to start. On cold start it cranks, fires and idles smooth. Drive 10 miles, shut it off and refire and the idle jumps 500 rpm up and down for 1-2 minutes then settles down. Repeats on restart until cold again. Plugs, coil packs and TPS underhood all new. If it were the ICV why only when hot for 2 min?


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Record a log file (rpm, coolant temp, MAF, intake air temp, STFT and LTFT, precat O2) at warm idle for couple minutes using OBDFusion, then we can see the intake air temp, MAF, O2 sensors and fuel trim.

[gheorghe]

Any resolution to this issue? My car does this as well and but the surges are not quite 500 RPM but same symptoms, only does it on hot restart. A buddy rode with me this weekend and has an '04 SMG and said his car does the exact same thing. Could it be the ICV?
I have no other running issues and no DTCs.

[PSUEng]

I've had this issue on occasion as well--but a handful of times. No codes. Otherwise idles super smooth, runs perfectly. I noticed it more in the brief time I was on a stock tune with full SSV1; post-HTE, no problem (knock on wood).

[SpaceJockey]

I've experienced this with all three of my E46 M3s. I remember seeing a thread about this on the old forum and a LOT of people said the same, including some original owners who bought their car new. I believe it was determined it was normal for the S54, but I could be wrong.

[Phoenix///M3]

Thx for the bump. Still no resolution but interestingly enough, in hot/humid weather, it will also do it on cold start. When I'm backing out of the garage just letting the clutch out it sounds like I'm in an F1 pit trying to keep the revs high enough, lol


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[ChapterM3]

I noticed something similar in my car tonight, except mine came with a cyl 4 and 5 misfire (CEL came on) - car would idle at 1k after being started hot, and only settle back to its normal 500rpm after being driven a bit. Misfires are audible during the hot start and not present at all during the 500 rpm regular cycle. This is a new one, but one that I logged in my service excel sheet 400 miles ago as potentially hearing a misfire. Any other news from anyone in this thread?