I have a 93 Formula with an LT4 short block, ported & polished heads, LT4 hot cam, Holley 52mm TB, Moates piggy back chip, long tube headers w/ Borla exhaust, no cats. When I start it for the first time, it runs fine. Once it heats up, it "missfires" (not sure if it's a miss or something in the fuel) really bad. It wont even stay running. Restarting it normally takes about 15 mins of constant trying. I sent it to the shop and they said it was switching in and out of closed loop. I did a search and found similar problems. Those were tracked down to the o2 sensors, but no one said that it wont stay running. So, first question; Will a bad o2 cause the engine to stall and not restart? Second question; any other idea of what it could be?
BTW I replaced the computer but that didn't help. Also, pretty much everything on the engine is new within the last 30k (opti, injectors, etc...)

 

Ok, I went back to the shop to talk to the mech. He said it's not the O2 sensors. He thought it was the computer too. Now, he is leaning toward the module in the opti. That sounds right, but I dont want to have to take of the front of the engine to find out that its not. Any ideas would be greatly appreciated.

 

do you have MSD box or something like it?

 

I'd start by checking the MAP sensor.

 

No. The ignition system is stock except for the msd plug wires.
Is there any way to check that without sending it back to the shop?

 

Easy to check with a scanner or a volt meter.

 

Well, I feel kinda dumb. The module is mounted to the coil, not inside the opti. That's going in today. I'll let you know how it goes.