Rough idle at start up (E36 M3)?

[ARCHER]

For the first time since I've owned it, the M3 balked a bit at first start up yesterday. It acted as though it was not firing on all cylinders for appx. 30 seconds and then all was well - no trouble the rest of the day or today for that matter. This car, even in temperatures bordering zero degrees, has never ran poorly or as TD puts it, sounded like farm equipment until warm. She's been as smooth as silk until yesterday.

Should I be thinking Vanos, Cam Position Sensor or none of the above? Could it be just a freak occurrence? :?

[zach]

For the first time since I've owned it, the M3 balked a bit at first start up yesterday. It acted as though it was not firing on all cylinders for appx. 30 seconds and then all was well - no trouble the rest of the day or today for that matter. This car, even in temperatures bordering zero degrees, has never ran poorly or as TD puts it, sounded like farm equipment until warm. She's been as smooth as silk until yesterday.

Should I be thinking Vanos, Cam Position Sensor or none of the above? Could it be just a freak occurrence? :?

Mine does this almost every time I start it.

It could be the cam sensor. If you have a code reader, run the codes and see if there's anything in there.

edit: my money's on freak occurance.

[ARCHER]

edit: my money's on freak occurance.

I'm inclined to agree with you. Let's hope we are both right.

[zach]

edit: my money's on freak occurance.

I'm inclined to agree with you. Let's hope we are both right.

and that I learn how to spell. :roll:

[TD]

The other thing it might be, which you didn't list, is that you might benefit from getting an ECU software update. When I was running especially rough in the AM, I recall doing a bunch of research online and the ECU software update was a often mentioned fix. I got it (I had to pay out of pocket for the labor) and things were much better afterwards.

Now, it still sounds a bit rough when stone cold on cold mornings (the "farm equipment" reference), but it doesn't stumble.

Also, make sure to check your oil level.

[JST]

For the first time since I've owned it, the M3 balked a bit at first start up yesterday. It acted as though it was not firing on all cylinders for appx. 30 seconds and then all was well - no trouble the rest of the day or today for that matter. This car, even in temperatures bordering zero degrees, has never ran poorly or as TD puts it, sounded like farm equipment until warm. She's been as smooth as silk until yesterday.

Should I be thinking Vanos, Cam Position Sensor or none of the above? Could it be just a freak occurrence? :?

Mine does this almost every time I start it.

It could be the cam sensor. If you have a code reader, run the codes and see if there's anything in there.

edit: my money's on freak occurance.

If it is the cam or crank sensor, it will trigger the check engine light.

[zach]

For the first time since I've owned it, the M3 balked a bit at first start up yesterday. It acted as though it was not firing on all cylinders for appx. 30 seconds and then all was well - no trouble the rest of the day or today for that matter. This car, even in temperatures bordering zero degrees, has never ran poorly or as TD puts it, sounded like farm equipment until warm. She's been as smooth as silk until yesterday.

Should I be thinking Vanos, Cam Position Sensor or none of the above? Could it be just a freak occurrence? :?

Mine does this almost every time I start it.

It could be the cam sensor. If you have a code reader, run the codes and see if there's anything in there.

edit: my money's on freak occurance.

If it is the cam or crank sensor, it will trigger the check engine light.

I was under the impression that the sensor can kind of gradually die, and only trigger the CEL after it finally dies.

[killerdeck]

Under no circumstances should you feel concerned. This has been an issue with all E36 and E46 BMW 3s as far as I can tell. I have personally experienced it frequently on a 98 323is, 00 323Ci, 02 325Ci, and now in my 04 330i. Funny this comes up right now as I have my car at the dealer investigating stuff, among which is this issue. I have been told by multiple dealerships and service techs that this is an issue BMW NA is working on a software update for. I keep getting told "Not much we can do at the local level until BMW NA updates the software." Hope this helps!

[JST]

For the first time since I've owned it, the M3 balked a bit at first start up yesterday. It acted as though it was not firing on all cylinders for appx. 30 seconds and then all was well - no trouble the rest of the day or today for that matter. This car, even in temperatures bordering zero degrees, has never ran poorly or as TD puts it, sounded like farm equipment until warm. She's been as smooth as silk until yesterday.

Should I be thinking Vanos, Cam Position Sensor or none of the above? Could it be just a freak occurrence? :?

Mine does this almost every time I start it.

It could be the cam sensor. If you have a code reader, run the codes and see if there's anything in there.

edit: my money's on freak occurance.

If it is the cam or crank sensor, it will trigger the check engine light.

I was under the impression that the sensor can kind of gradually die, and only trigger the CEL after it finally dies.

Not sure. When the cam position sensor on my E46 went, it went gradually, but whenever it gave a reading out of range, it would trigger the CEL. The symptom was thus an intermittent CEL. I don't know whether the crank position sensor would behave the same way, but I imagine it would.

[ARCHER]

Thanks for the responses, gang.

My oil level is good (try to check it every two weeks) but I will check into the ECU upgrade for certain.

I assumed that if the cam sensor was going, the check engine light wouldn't lie back for it but it sounds as though this could be up for debate as well.

Regardless, it is about time to put some money in the car. It needs brakes, a new ICV and perhaps an ECU upgrade.

[Rob]

How old are the plugs? It's not a likely cause, but you never know. They recommend changing them every inspection 2 for that car I think.