lean idle after warm up.

[atlpd3147]

I've been battling this issue for a while now and im still stumped.
I have a vpc/safcII combo with a plx R-500 wideband and I need help.my car starts ok, when I turn her on I get normal airfuel readings but after a few minutes when the car starts getting into warmer operating temps my airfuel readings on my wideband show lean and the car seems to have a noticable miss. What can that be. There might be something that is wacked out but I don't know what it is.

 

[isnms]

i had a lean idle. tracked it down to a hole in the intake manifold gasket.

 

[atlpd3147]

Isnms,
Can you elaborate on your reply? How did u find the leak? Any other info you want to share thanks

 

[isnms]

my zt2 was showing a lean idle. VF was sitting on 5 and a/f would rise to 15, 16, 18, 19 a/f. Then it would run terribly rich at wot, 9.9, 9.6, 9.5 a/f.
I tried checking all the vacuum hoses, accordion hose everything. Finally I took it to a local Goodyear shop to put it on the smoke machine. They found the hole in the intake manifold gasket.

 

[atlpd3147]

Another thing.
When the car is cold(started after sitting for over nite) I get a very rich mix. 10.1 or so.
That I have to lean out the fuel on the safcII at the 800 rpm range. But if I keep the safcII lean in that rpm range when the motor get to warmer temps I get a lean condition. Its as if I need to take fuel out when cold then add fuel in as the car warms up. This is all @ idle. Anyone have any suggestion?

 

[atlpd3147]

Ok man.. That sounds like what I have. I will get a check for any air leaks in my intake system asap

 

[isnms]

probably because it's cold, the hole is sealed up, wherever it is. and the fuel adjustment has been adjusted because it normally thinks it's lean at idle and is dumping in more fuel, thus rich on cold idle.
then as it warms up, the hole opens, sending you lean.

 

[atlpd3147]

Thanks man..