96 Sub chuggling problem
rbeechan
03-22-2006, 08:20 PM
I am having problems with my 96 K1500 Suburban. My mechanics and I have been scratching our heads trying to figure it out. It started about a year ago when I had my neglected trans rebuilt at 95k. Upgraded to a heavier duty T/C. On the way home from trans shop, get check engine light. Return to trans shop and they read code PO300, random misfire. Drive vehicle for a few weeks and on a trip, after exiting freeway, engine sounds like tennis shoes in the dryer. Broken crankshaft. Local shop installs new GM crate engine. Continue to get PO300 engine code. Local shop tries various fixes, plugs, cap, rotor, wires gas additives... No noticeable driveability issues, just the C/E light. Finally find the condition where it happens most, 2500 rpm at cruise, light throttle. Start to feel what seems to be engine miss during these conditions, chuggling (per GM manual). Becomes very evident, my wife can noticw it from the passenger seat. It will happen at anywhere from 1800rpm to 2800rpm. Not with foot off throttle and not during moderate to hard acceleration, just light cruise. Local shop can't figure out, take it to Chevy dealer. They read codes, replace o2 sensor, no help. They do injector flush, check cylinder head, check cylinder head again, performed repair on both cylinder heads per service bulletin. Replaced injector(s). Each thing on seperate visits. No help. Most work at dealer is performed under warranty. They now want to separate the engine and trans to inspect flex plate. I find it strange they are looking to the trans as a possible culprit, since coincidentally that is when the problems started.
Sorry for the lengthy post but I thought it important to describe as many details as possible. If anybody has a similar experience or idea, I would greatly appreciate it. Thanks
Sorry for the lengthy post but I thought it important to describe as many details as possible. If anybody has a similar experience or idea, I would greatly appreciate it. Thanks
bndfishing
03-22-2006, 11:25 PM
The way you are able to narrow down the rpm range makes me suspect it might be a TPS. These kind of problems can really make you loose your hair, the only way it can be worse is if it were a Ford.
NoEcm
03-23-2006, 12:52 AM
Have you looked as TSB 77-71-53:
"A computer reprogramming can get rid of persistent chuggle/surge on the highway in 1996-97 GM trucks with the 5.7-liter V8 and 4-speed automatic. Fuel economy will be affected. Technical service bulletin (TSB) No. 77-71-53."
"A computer reprogramming can get rid of persistent chuggle/surge on the highway in 1996-97 GM trucks with the 5.7-liter V8 and 4-speed automatic. Fuel economy will be affected. Technical service bulletin (TSB) No. 77-71-53."
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