Rough and lean cold idle condition

rzimmerl

Registered User

• Jun 30, 2009

• #1

For the last 2 months about right after the Dayton spring meet my car runs extremely rough and stalls at cold idle. AFR is about 18-19 for about 2 mins then the idle settles out to 14.7. Throttle body is adjusted right, new TPS set to .95 volts, MAF is clean, all vac lines checked good, out of ideas???

 

S_Mazza

Registered User

• Jun 30, 2009

• #2

It almost sounds like your idle fuel settings are off and it doesn't level out until the closed-loop kicks in. Is the car tuned? What device are you using?

 

rzimmerl

Registered User

• Jun 30, 2009

• #3

Yes it is tuned by SCU a couple years ago, a few bolt on mods have been done since. Base fuel pressure is set at 44psi, to maintain 11.8 AFR under full throttle.

 

S_Mazza

Registered User

• Jun 30, 2009

• #4

Hmm, if you didn't change the tune, then maybe it's a sensor? Like the ECT?

 

rzimmerl

Registered User

• Jun 30, 2009

• #5

I've been thinking the ECT, its about 2 years old and not very many miles.

 

XR7 Dave

Registered User

• Jun 30, 2009

• #6

If it's something that wasn't there before and now is, then it's a vacuum leak.

 

rzimmerl

Registered User

• Jul 1, 2009

• #7

Well, this is going to be fun. All vac lines are new, attached and hose clamped, IC connections are tight. Guess the next step is pull the blower off and check the inlet to case seal.

 

S_Mazza

Registered User

• Jul 1, 2009

• #8

Hmm, did you check the crosstalk tube between inlet and return plenum? That can leak pretty badly without any visible cracks.

I was also thinking, you can check the MAF reading with a voltmeter and see if someone knowledgeable (*cough* dave *cough*) can tell you if that seems too low (vacuum leak).