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Check your Distributor, and check for the presence of spark with a timing light. I had an 88 C2500 with over 250K miles, that started shutting down intermittently when warm, but would run when it cooled. Watching the injector spray pattern, as the miss started kicking in & getting worse, the injectors would cut-out intermittently, leading me to think that was the cause of the misfire or no-fire problem. Changed fuel filter, pump, TBI harness, etc. Finally found someone who had experienced same. They said change the distributor! Couldn't hardly believe it, but got $50 boneyard dist, dropped it in, and problem solved. A racing mechanic with factory Chevy connections later told me the ECM has to detect an active spark pattern from the dist, or it cuts off TBI activity (for safety's sake - in case of accident, stalling, etc). He said the dist caps on those HEI's form little chunks of white crusty material on the inside terminals, due to the high voltage. This stuff is conductive, and if the cap is not changed periodically, those little white balls fall down into the lower dist body & create short circuits that can cause total dist failure, or random/intermittent spark failure, which then triggers the ECM to shut down the fuel injection system. Made sense to me, and perfectly explained what I had experienced. I change the dist caps on my trucks regularly (every 1-2 years/30-50K miles) nowadays.
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08-31-2004, 10:46 PM
