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I have a friend that is working on a 2000 Silverado with 5.3. It has a misfire on 7 and 8. Has 7 and 8 misfire codes, had a knock sensor code, and an o2 sensor code. He has replaced the knock sensors, plugs, wires, number 7 injector and coil. Has good compression. Any Ideas? GG?
Anyone?
Did he replace the KS harness as well as the sensors? Does it make any audible noises? Possibly a mechanical problem causing the misfire. The rear injectors are known to catch sediment and rust from the rails. Make sure they're not clogged and if they are, flush the lines and rail. Check fuel pressure. Also might check exhaust backpressure with a gauge if equipped with cats.
I dont think the harness was changed. It does has good fuel pressure though. I will have him check on the cats today. It does has 160,000 miles
I meant the small KS harness, not the whole thing.
My 01 Z71 did the SAME thing. The rear injectors were clogged up, I did every thing I could to unclog them and nothing worked had to go get a couple from the local salvage yard, put them in and changed the clogged up fuel filter and she ran great, just my .02...if that
Replaced y pipe today with the one off of my truck and saw no improvement. It is giving a P0200 and a P0300 which deals with injectors and random misfire.
200 and not 201 202 203 etc?
Check the injector A and injector B fuses. The only things that can cause 201-08 are an open injector wire, open fuse, shorted injector wire, PCM, open injector, shorted injector. If it runs on all but 7 and 8 then there is no blown fuse. Sounds like someone has been poking the injector terminals with a tester. Splice in two new GM pigtails for those two and recheck.
P0300 is about as useful as the PCM telling you what color the truck is. In the old days the PCM would actually set 301 302 etc.
Yeah I just used a cheap scanner after we did the y pipe. Im going to put a good scanner on it tommoro.
Someone told him he needed a pcm and have it reprogramed. Heard of this?
Sure. Been around lightning? I mean the kind from the sky. Needs scanned.
He found a pcm for 50 bucks and the dealership said they would reprogram it for 41 bucks. I didnt think that was to bad. He said he could pull off all of the injector wires one by one and they would all make a difference except on 8. But today he did it and 7 wouldnt make a difference.
Then noid light those two and see if they blink. If not suspect either the PCM or the pigtail.
Gonna put the noid light on it in the morning. Thanks for your help Nate.