Rough Idle - S52

[De'Auntre]

Okay, this one's kinda vague, so I'm really looking for anything you got in the way of shared experience.

I've had the S52 for half a year or so, it's about to roll over 40k miles. I usually drive it only on weekends, so its habit is to sit for 4 or 5 days in the garage in between runs.

A week or two ago, I started it up and immediately the idle was so rough the car shook violently. I'd never experienced that before, so I was a bit unnerved. No CEL. I turned the car off, waited about 30 seconds, and rebooted. Same thing. I gave it a little gas and it smoothed out almost completely, but when I let off the pedal, it went right back to it. This time I let it run for 12 seconds or so, still no CEL, then shut it down again.

I gave it about a minute, then tried again. Still idling rough, still no CEL. I decided to try to work it out, so I took it for a gentle spin around the block. After a few minutes of driving, the roughness at idle had disappeared completely.

It hasn't happened since.

Now, I know the general causes of rough idle, like lack of compression; lack of proper spark (gap, timing, etc.); and lack of fuel. My initial guess, based on the way the problem fixed itself with the RPM increase, and the fact that the car hadn't been cranked in a week is that it is fuel related. If the rough idle returns, I'll go ahead and start the troubleshooting myself, but I'm presenting the situation here to see if any of you folks have experienced this same thing on your S52...

Thanks for any input.

[chip4]

Sounds like "cold start issue" -do a search, most likely solution: software upgrade

[crusher]

i've been doing that same thing lately running the coupe on weekends only and never had the cold-start problem yet. knock on wood.

[De'Auntre]

Sounds like "cold start issue" -do a search, most likely solution: software upgrade

Thanks for the response. I'm pretty familiar with others' comments regarding the "cold start" problem being certainly software related in S54s. As you probably know too, seems many folks with e36 Ms who believe they may have cold start problems are also told that it's software related by BMW. Seems most say that the OEM upgrade for S52 doesn't help. Many of the owners on this and the other 2 principal fora that believe they have the cold start problem on S52s seem to indicate that it's a recurring condition.

The fact that it's only happened once, gives me cause to seek more info.

[6i9]

My 99 M Coupe has had this cold-start issue only once since I've had her. This did scare me a little, but found out it was a common problem. It hasn't happened since then, and I have a Dinan chip. I dno't know if that makes a difference?

[Rook]

The S52 Secondary Air System is common to run in the mornings for appx 30 seconds when the car is first started, it will make the car idele rough but not to the extent that you're seeing. Thats odd, also odd your CEL didn't come on.

I suppose its possible that you have a leaky injector, although not very common on these cars. The leaky injector could be leaking fuel down into your cylinder, causing it to run like crap after you first start it. Although, that would probably also clear it self up quicker than 12 seconds.

Hmm.. I have a 99 M Coupe that sits for days at a time as well, even up to 2 weeks, never has it given me this type of problem.

[littlelee1]

I've got the 2.8 litre, and if I do not drive her for like a day and go to start her up (remember its always 85+ degrees in texas even in the mornings) and my car will shake pretty bad for about 15 seconds then all of sudden it will smooth out and everythings fine.

First time it happened I immediately opened the throttle a little bit thinking something was in need of getting "cleaned" out. It stopped for a sec then started again. So after time I have come to realize, let it sit for about 15 seconds and it should be done.

[De'Auntre]

Cool, thanks for all the info fellas.

Awful hot here where I am too... :sun

[littlelee1]

Cool, thanks for all the info fellas.

Awful hot here where I am too... :sun

TOO hot :