Thread: 1991 Chevy 454 backfires, runs good, backfires, sometimes cycles
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Old 03-31-2009, 07:42 PM
pjksr1955 pjksr1955 is offline
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Re: 1991 Chevy 454 backfires, runs good, backfires, sometimes cycles
Shortbus, When I jumped the ALDL... A and B terminals nonthing happens. I have to check for a broken wire. Even when I disconnect battery for a couple days, the service engine light will not clear. It stays on...Thanks, Pjksr1955
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Originally Posted by Shortbus View Post
I'm going to move this thread to the C/K forum.

Onto your problem. If it always runs smooth on a cold start then your pcm must be working ok since its operates off of predetermined information stored in the pcm. That is rather than taking data from sensors on and around the engine it is running in closed loop until the engine coolant reaches a specified temperature. Thus the engine should be mechanically sound and there is a faulty sensor sending bad information to the pcm once the system goes into open loop and begins to use information from sensors to adjust fuel ratio, timing ect.

There are lots of things it could be. A dirty IAC valve, this is mounted to the TBI with two torx screws with a little pintle that controls airflow in the TBI. It could be injectors with a bad spray pattern.

When you jumped the ALDL did the ses flash a code 13 and then some other codes?
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