misanthrope
Full Member
2004 Avalanche 5.3 ~130k miles.
Engine began to run a little rough in town at about 25mph. After about 10 minutes of driving engine light came on. Turned onto 30mph road to head home and light starts flashing. Slowed down under 30 and it was solid again, stepped on gas and light would come on at 2000 rpm even if under 30mph. No power.
Ran code, random misfire. Used IR heat gun to check Cats, driver side upstream 390F/downstream 500+, passenger side upstream 410F/downstream 289F. Replaced with new catalytic converter assembly, all 4 o2 sensors(never been changed). Fired truck up and idle was still not smooth, when I let off brake in gear, engine is pretty rough. Ran code, random misfire and cylinder 7 misfire. Swapped all spark plugs with oem, checked for spark on all coil packs and wires, found good. Engine ran same. Swapped cylinder 7s coil pack and spark plug wire with cylinder 5 but code stayed on cylinder 7. Returned coil pack and spark plug wire to original position. Had a shop run fuel system on their machine, same symptoms. Engine began shutting off on its own, cleaned out throttle body with cleaner and engine stopped shutting off after start up. Pulled injector 7, had build up inside. Replaced injector, truck ran like a champ with no codes.
4 days later, engine started running rough very gradually the more I drove, code flashing at 25mph or any speed for that matter...Random misfire code again. Swapped fuel rails and injectors with oem (got em all for $200 new, couldn't pass it up Drove around and it ran great, could feel engine still felt like it was missing but very slightly if that makes sense, no codes. Drove down highway and it ran great, stepped on gas and it felt like something gave and the engine power went away again with the engine light blinking.Checked plugs, wires, coil packs(swapped again) to make sure it was all hooked up properly, found original plug wires on plugs a bit loose so I swapped out to MSDs since they were they same price, still no change. Code still flashing when I drive but at 25 now instead of 30mph, rough idle, no power, engine feels like it's pulsating from the misfire when I drive. Have not pulled injector 7 to see if it was clogged again.
Thinking back to when the engine felt like it gave way and the power disappeared and the clogged injector from the first time around, is it possible for it to have been charcoal? I only ask because I keep seeing the evap canister tsb whenever I search for my misfire on cylinder 7. Don't think it's fuel contamination, I ONLY run 90 octane(highest I can get from the 1 gas station in town) and as to the quality, your guess is as good as mine. Oil gets farmed out of Alaska yet we pay more than all you guys in the lower 48, how does that make sense?
Anyways, I THINK I may hear a vacuum leak but I can't be sure. I haven't checked the vacuum or sprayed it around where I hear the noise(it could just be me imagining the belt sound making a vacuum noise).
Any ideas are welcome, this is getting silly. Fortunately I had the intention of changing things out one at a time so I don't feel so bad, this just all came at once a little sooner than I wished
Thanks in advance!
Engine began to run a little rough in town at about 25mph. After about 10 minutes of driving engine light came on. Turned onto 30mph road to head home and light starts flashing. Slowed down under 30 and it was solid again, stepped on gas and light would come on at 2000 rpm even if under 30mph. No power.
Ran code, random misfire. Used IR heat gun to check Cats, driver side upstream 390F/downstream 500+, passenger side upstream 410F/downstream 289F. Replaced with new catalytic converter assembly, all 4 o2 sensors(never been changed). Fired truck up and idle was still not smooth, when I let off brake in gear, engine is pretty rough. Ran code, random misfire and cylinder 7 misfire. Swapped all spark plugs with oem, checked for spark on all coil packs and wires, found good. Engine ran same. Swapped cylinder 7s coil pack and spark plug wire with cylinder 5 but code stayed on cylinder 7. Returned coil pack and spark plug wire to original position. Had a shop run fuel system on their machine, same symptoms. Engine began shutting off on its own, cleaned out throttle body with cleaner and engine stopped shutting off after start up. Pulled injector 7, had build up inside. Replaced injector, truck ran like a champ with no codes.
4 days later, engine started running rough very gradually the more I drove, code flashing at 25mph or any speed for that matter...Random misfire code again. Swapped fuel rails and injectors with oem (got em all for $200 new, couldn't pass it up Drove around and it ran great, could feel engine still felt like it was missing but very slightly if that makes sense, no codes. Drove down highway and it ran great, stepped on gas and it felt like something gave and the engine power went away again with the engine light blinking.Checked plugs, wires, coil packs(swapped again) to make sure it was all hooked up properly, found original plug wires on plugs a bit loose so I swapped out to MSDs since they were they same price, still no change. Code still flashing when I drive but at 25 now instead of 30mph, rough idle, no power, engine feels like it's pulsating from the misfire when I drive. Have not pulled injector 7 to see if it was clogged again.
Thinking back to when the engine felt like it gave way and the power disappeared and the clogged injector from the first time around, is it possible for it to have been charcoal? I only ask because I keep seeing the evap canister tsb whenever I search for my misfire on cylinder 7. Don't think it's fuel contamination, I ONLY run 90 octane(highest I can get from the 1 gas station in town) and as to the quality, your guess is as good as mine. Oil gets farmed out of Alaska yet we pay more than all you guys in the lower 48, how does that make sense?
Anyways, I THINK I may hear a vacuum leak but I can't be sure. I haven't checked the vacuum or sprayed it around where I hear the noise(it could just be me imagining the belt sound making a vacuum noise).
Any ideas are welcome, this is getting silly. Fortunately I had the intention of changing things out one at a time so I don't feel so bad, this just all came at once a little sooner than I wished
Thanks in advance!