Random Revving 1M

[etr2016]

About 3 months ago I had a CEL for a DMTL issue. I replaced it myself (and thought I might also need to replace the charcoal canister, but I've driven the car 300 miles since and the CEL hasn't come back on). Anyway, so it's been about 3 months since I've driven the 1M, and when I turned it on today, it had this really random revving at idle. I thought the battery was going to die because that is how low the rpm got. I drove it over to the dealer who said it wasn't the injectors because it would throw a CEL if it was, and they suspected that there may have been an issue with the charcoal canister still. They recommended I drive it to "burn it off." After driving it about 40 more miles the problem went away. I have a feeling this won't be the last time I see this issue. Any ideas? HPFP? Here is a video:

[MDORPHN]

I'd try throttle adaptation reset procedure.

Push Engine button ON (once; do not start engine)
Step on the throttle pedal down (all the way down)
Hold it there for 30-40 seconds
With throttle still down, push Engine button OFF
Release throttle
Wait 2 minutes
Start car normally.


Neil

[etr2016]

thanks, Neil! I'll definitely try that.

[nachob]

When my fuel pump went out it was more violent than that. It sounded like the car was running on 1 cylinder and trying run on two. There are probably different symptoms but that that was different than mine. My HPFP went out at 10k miles on my first 1M.

[etr2016]

Does anyone think this could have been condensation in the fuel tank? The temps here were between 35 and 70 degrees for the time it was stored (in a garage of course).

[nachob]

Originally Posted by etr2016

Does anyone think this could have been condensation in the fuel tank? The temps here were between 35 and 70 degrees for the time it was stored (in a garage of course).

I don't think it would be condensation in the tank. Condensation in the engine is more common . My car idles a little rough after sitting a few weeks. Then if you drive it a day on a long drive it purrs after that. Condensation can build in the engine but once you burn it off the car will settle down. Yours seems more dramatic than condensation in the engine. You would be surprised how sensitive these engines are to changes in the engine pressure. For example if you forget to put the oil cap back on the car will run very rough even for a bit after you put it back on. If your car sits it is very likely to develop intermittent things like this from condensation in engine and even oil. If it happens again and the car is sluggish to accelerate then it could be the HPFP. If it accelerates normally from this funky idle then it's something else. My car runs perfectly if I don't let it sit more than a couple of weeks. If it sits a long time the idle will have a slight miss but it goes away completely after a long drive and won't happen again until I let it sit a long time. I'm pretty sure it's just a little condensation in the engine burning off.

Has it come back again for you?

[etr2016]

No, it hasn't come back - but all I've done is started it a few times. When I first started it after sitting for 3 months it was immediately evident!

I'm taking it for a long drive tomorrow.

The car seems to have enough power. Oddly, I swear that the traction control is way more sensitive. The car was actually slow through first great because the traction control was limiting the power. It could have been the road as there was a storm that came through putting a bunch of dust and crap on the road. Once I was in second gear it pulled normally. It seemed slower pulling from 80mph, but again, I haven't driven it in so long I sort of forgot how fast it is at 80mph. I guess I'll know more tomorrow.

[etr2016]

Just finished a 100 mile mountainous drive without issue. The joys of German cars...