Idling fine and then.....

[91TalonTSiCT]

Well I got my car started after doing an engine swap and it was idling fine for about 5 minutes-oil pressure good, A/F starting to warm up and then the engine starts to stumble and the A/F starts to back down way lean. I have an auto tranny 1g with 14b, 450s, MT cams, and EPROM ecu. Could it be bad fuel or O2 or something else?

 

[snoozin]

if its starting after your car is already warm it could be a leak. i had the same problem. it would idle fine at 1500 - 2k while cool then it would warm up and idle around 800 and it would start bouncing between 1500 and 400 and would eventually die, i did pressure test and found a leak in my hose that connects to the wg, was a little slit that only let air out under higher pressure and i didnt even find it until was went through all my hoses and rolled them around to see if they were cracked. well this one was. i cut the piece out and reconnected and it idles like a dream now. it solved my problem of running rich occaisonally as well. thats the first step i would try before dropping money anywhere else.

 

[91TalonTSiCT]

I should have mentioned before that Im using the Taboo vac setup, but I am getting a lean reading from my a/f when the car heats up. Any reason why this could be?