Hi...I am teh super n00bs on the forum and am having a huge problem.

To start, I have a dropped 03' GMC sierra 1500 with a 4.8l vortec w/ about 55k miles on her. About a month ago I got a code for catalytic converter. Had it cleared and continued on for another couple days and then the code came back and started to have a rough idle and no power. I took a look and found a flat spot on the cat from it being hit. So I replaced the cat Y pipe, found it was clogged and all the "inards" poured out of the side that was hit. Bolted everything up and it was running better, but still a rough idle. Went back to autozone and checked the code. Got cat, random missfire, MAF, and o2 sensor codes. So I got a new o2 sensor, plugs, and plug wires to see if it will fix the problem and no dice. Went to fletchers auto to have them clear and recheck the code and its just a random missfire now. I had them run a diagnostic and they figured it was the intake manifold with a vacume leak. There's a TSB report out on the manifold gaskets and possible warpage of the manifold and when they ran their computer, it came up a missfire in cylinder 8 with 7 trying to comensate. So I went back to Autozone and picked up gaskets and replaced them...No dice. When I went back to autozone they said another thing could be the fuel injectors not sealing properly or the fuel injector itself. Cause I had a realization that I had 2 weeks prior put fuel injector cleaner in the tank. So I did the "screwdriver handle" test and listen to the injectors. They all seem to be running fine cause I hear each one click. So I pulled them and replaced the O rings on all 8 to be certain and still missfiring/vacum leak! I really dont want to replace the manifold cause thats $300 I dont have but I need it fixed. Is there ANYTHING else I havn't tried yet that can work???

Thanks,

Travis

 

Did you gap the plugs or leave them as tehy came out of the box when you installed them? I had a friend do a tune up on his Tahoe and regapped the plugs and bent the electrode accidently. Anyhow that is what was causing the same codes you are describing. Also did you buy a good set of wires or the cheap A$$ autozone wires? If you did get the cheap ones return them and upgrade to Bosch or AC Delco. And what plugs did you instal? If they are not Iridium then that could be a problem too. These motors like Iridium plugs unless it is a fully modified motor. Just my 2 cents. You could also try cleaning your MAF with MAF cleaner in the spray can.