Misfiring question

[25centguy]

My car has been having a rough idle on cold starts. When I start it the idle is at 1200 rpm and then its like the engine is misfiring because I can feel it shake and then the idle goes up to 1500rpm slowly idles down and then when it gets warm has a nice idle at around 750rpm. Someone said he was having the same problem and when putting back the stock ecu everything was ok. Any ideas?

[hackish]

Can you post a list of mods? In general I don't normally change the fuel or timing settings for the idle portion of the map.

-Michael

[25centguy]

List of mods: not much

AEM CAI
Full exhaust with OBX header
RRM UDP

[hackish]

Should be no real effect there. It is possible that your MAF or primary O2 sensor is starting to die. After a flash is done it's normal to have a little bit of rough idling while the ECU re-learns the idle throttle positions.

-Michael

[darewood]

Exactly what Michael said, but the idle goes up also because of the operating temperature so low. If you have the editor and the tune you can see at what temperature corresponds to what rpm the car will idle at. Once the car is warm it will go to the standard 750 I think it is. I have mine set at 1,000 just because I have a stiffer motor mount haha, so I don't really remember what stock idle sits at.