so another guy at the shop I'm at put in 6 Bosch reman injectors last week. customer took truck and said it ran great for 200kms then it started acting up, knocking, low power pulling a 5th wheel up hill and it was hard to start in the mornings, and a rough idle. my boss checked the cylinder contribution or cylinder performance test, 1,2,3 were at 101%, 4 was at 103, 5 was at 88 and 6 was 104. I took the valve cover off and checked the resistance of all the injectors and got 1.2ohms on each which is spec for new ones. I check the harness in the gasket all the wires were .7ohms. I checked spec it said .5ohms, but no problems on 1,2,3, so I figure it must be good. doing research of these symptoms I read that maybe one of them could be clogging up, and I thought this may be possible since the back 3 injectors are under the firewall and there is insulation hanging down over it with debris and dirt falling so I thought maybe something fell in an injector bore before the new injector was put in and it worked it self down. so in my reading it said check the fuel filter, change if necessary but put like a 1/4 litre of injector cleaner in the fuel filter housing then the rest in the fuel tank. changed fuel filter, found lid was loose, put injector cleaner in housing, let it run for a while then took it out on the highway and opened it up a bunch. came back and did another cylinder performance test. 1,2,3 still about 100%, 4 was 102%, 5 was 94% and 6 was still 104%. a bit better, but still a rough idle. no programmer in this tuck either. any one have any experience with this. if I can't figure something out quick, my boss wants me to swap around the back injectors to the front and see if anything changes. I'm not looking forward to the valves. I know the other guy that changed them did a complete valve adjustment after, the truck has 375000kms on it.
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2003 Chevrolet Silverado 4.8l w/4.56 gears
2002 Chevrolet Silverado 5.3l
2001 Chevrolet Silverado 6.0l eclb