Bad cold idle?

[STEEDA85GT]

Just had the car switched from speed density to mass air and am happy overall with the improvement but the idle is still kinda rough when the car is cold. Not to the point where it's undriveable but it stumbles first thing in the morning consistently when I leave for work. Engine mods are CAI, e-cam, cobra intake, offroad H and cat-back. Previous owner had indicated it may have one bad O2 sensor and I never got around to replacing it - do they play a large role in the mass air system?

Also seems to idle really rough if I've been driving for a while, shut it down (for gas or whatever) and then start it back up. Not sure if the two issues are related...maybe vapor lock on this one?

Somewhat tough to diagnose over the computer but any help would be much appreciated.

Thanks

 

[jrichker]

See "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

Pay special attention to the CAI section in the Surging Idle Checklist. There may be a clue to your problem.

 

[93lxdm78]

I would reset the computer so your car can learn the mod. Also are you getting backfiring ?

 

[4G-KDMP]

have you checked to make sure all your vacuum lines are connected properly?

 

[STEEDA85GT]

I would reset the computer so your car can learn the mod. Also are you getting backfiring ?

Not terribly but it has backfired a couple times - how would I go about resetting the computer? Not sure if this was done on the install or not but it can't hurt to try...

 

[93lxdm78]

try raising your fuel pressure. the new mass might make it run to lean on cold start up raise it 2 to 3 psi see if that helps. I am assuming here the back firing is coming from the from not out the back.