Cold start unhappiness

[Jay 535i]

It's just recently got really cold here (~5degC and under), and sometimes (not always) when I start my car, it idles very unhappily for a few seconds. The revs rise and fall and the engine sounds like it might stall. If I press the gas while it's doing this, there's a delayed response before the engine revs a bit -- but not as much as the pedal movement should call for.

It sorts itself out after about 15 seconds, and doesn't happen with a warm start. I'm sure there's no harm being done, but it sounds bad and makes me look like an uncaring lout. Who, after all, would allow a BMW to fall into such abject disrepair?

I think it's most likely a vacuum leak somewhere that only becomes a problem when the materials contract a lot in the especially cold weather.

Any thoughts?

[Kalevera]

Just the DME going "oh **** it's cold!". You could cut out the IAT sensor and see what happens instead, but that'd probably not be a smart idea.

Revs probably shouldn't rise and fall -- it might run rough for a few seconds, though. Lots of mechanical things to get moving, cold oil, and a cold ambient temp in the engine do this kind of thing. No vacuum leak would disappear within ~ 15 seconds of starting the engine. Maybe air in the fuel line, but you'd have other issues then.

best, whit

[Jay 535i]

Just the DME going "oh **** it's cold!". You could cut out the IAT sensor and see what happens instead, but that'd probably not be a smart idea.

Revs probably shouldn't rise and fall -- it might run rough for a few seconds, though. Lots of mechanical things to get moving, cold oil, and a cold ambient temp in the engine do this kind of thing. No vacuum leak would disappear within ~ 15 seconds of starting the engine. Maybe air in the fuel line, but you'd have other issues then.

best, whit

Thanks, Whit. The revs don't rise and fall much. It seems like the computer is hunting for an idle speed that runs smoothly.

Oh, I should've added that when this happens the Check Engine light comes on, then goes out and everything is fine. I get stomp code 1222.

[632 Regal]

have you tried resetting the computer before the car is started cold?

Thanks, Whit. The revs don't rise and fall much. It seems like the computer is hunting for an idle speed that runs smoothly.

Oh, I should've added that when this happens the Check Engine light comes on, then goes out and everything is fine. I get stomp code 1222.

[Jay 535i]

have you tried resetting the computer before the car is started cold?

No. How do I do that?

[BMWDriver]

Could it be your E.A.T. chip that is not "used" to the cold ? (either programmed or designed for...)

[Alexlind123]

One of the first cold nights when my car was parked outside happened to be the same time i reset my computer. When i first started it it sputtered and coughed and made some nasty smoke, but then ran great and has never done it again, this was probably a month ago.

[Jay 535i]

One of the first cold nights when my car was parked outside happened to be the same time i reset my computer. When i first started it it sputtered and coughed and made some nasty smoke, but then ran great and has never done it again, this was probably a month ago.

Okay, so how does one go about resetting the computer? I can't find a CTRL, ALT or DEL key anywhere!

[ejhiggins]

disconect your battery cables and touch them together for (cables only not battery terminals) for 30 min,make sure if you have the oem radio to have the code handy you will need to re-enter it later on,you could keep the cables together with clamps or chanelock pliers, after 30 min reconect the battery start the car and let it idle for 10 minutes without touching the throtle, this will reset the computer.

[Jay 535i]

disconect your battery cables and touch them together for (cables only not battery terminals) for 30 min,make sure if you have the oem radio to have the code handy you will need to re-enter it later on,you could keep the cables together with clamps or chanelock pliers, after 30 min reconect the battery start the car and let it idle for 10 minutes without touching the throtle, this will reset the computer.

Thanks.

Now I gotta go dig up that radio code...