2002 Avalanche 5.3 O! M! G!

Hi, my name is Rich… and boy do I have a nightmare truck. First I had misfire problems P0300. I’ve replaced the fuel pump 3 times before I got one to run at the right pressures. You get what you pay for is all I’ll say on those pumps. I had to replace a few gas lines and changed the fuel filter while I was at it. On the 3/8″ line it kinked a little a 90 bend and hoped it wasn’t too bad of a restriction. I have good fuel pressure now, 50 psi idle 59 psi revving… had replaced the MAF and MAP sensors. Was getting misfires all over the place but mostly on the even number bank side. Replaced the fuel injectors with rebuilt upgrades. They have 4 holes instead of 2 and have less of an opening pressure (28 psi)… whereas the old injectors were like 50-55 psi range. Had also replaced all the coils, plugs and wires as a basic tune-up because my daughter just bought me this truck out of no where… but it had a lot of problems we weren’t aware of. The new injectors took care of 90% of the misfires.

Now I no longer get the P0300 but get P0174 and P0171 now. Done smoke tests, nothing. Then I bought a used GM Tech 2 and saw my fuel trims were really out of range after watching your videos to learn how to use it. I thought it was a vacuum leak again being illiterate and tested again for a leak with the smoker, nothing again. Then had written to you off of one of your videos and giving you misinformation I led you to think my MAF was bad. I had replaced it before but defective parts happen so I exchanged it for another new one.

The first day I drove it my LTFT was at 16 and 14 and my STFT were bouncing back and forth around 0. I thought it was running better and that maybe I just had a remaining vacuum leak.

Well today in driving the fuel trims were back to their normal tricks: LTFT both sides pegged at 25 and the STFT jumping around between 10 to 16%. Driving it further fuel trims bank 1 was the same but bank 2 had a LTFT of 25 and a STFT of 54… Then I look again and both fuel trims on bank 2 went to 0 as well as O2S1 sensor was 0 and I did have a infrequent heater code for that O2 sensor. So I’m hoping that changing that O2 sensor will solve a lot of problems on bank 2. But I don’t it will specifically will take care of the P0171 and P0174 problems… or will it? Thanks… I hope I’m doing this in the right place for I have paid for a membership and am kind of lost still… lol.

Added info: I do have a frequent misfire on #6. Compression is 135 and changed the coil and plug again. Never changed the wire though because I had already changed it. But, since changing the fuel injectors if that engine is going to misfire, it does it mostly of #6. Depending on the weather I’ll run out tomorrow and swap wires to see if it follows.

5.3’s are noted for intake leaks… I did the water test and brake cleaner but I think I looked at the scanner wrong one time and didn’t have the scanner the first time I did it. I was watching for the engine to run rough but really never did… and I’m still illiterate about all this. Lol, thanks again