So....as you all know I've been having many problems with my engine. When I cruise on the highway, only when the blower is on w/inside recirculate or A/C, my truck stumbles every know and then...like it misses a beat. I noticed that this was much worse with a 93 octane "hot tune" in there (increased timing?). Most people chalked it up to the A/C compressor coming on and off, but I just never remember it doing this, nor do I think GM would release a vehicle performing like that. Some posted though that this could be a sign of weak coils/bad coils. My coils are the original 2000 coils....which are the weaker ls1 type compared to the newer 6.0/ls2 coils. Plus they are old. Recent WOT logs I have shared with Blackbear (Justin), he seems to think I may have a misfire problem causing the huge KR issues at WOT. For some reason every time I go WOT I get a weird reading from the bank 1 o2 sensor...say it's at .900mV initially then it just randomly goes down to .750mV which corresponds to the huge spike in KR (up to 8 degrees). The thing is....I have never had 1 single misfire code. So, does it seem possible to my coils be weak or misfiring, with no code?

 

My buddy's truck misfired without codes. He had a small crack in one of his spark plugs.

 

I already bought 8 new TR55 plugs. I'm debating buying new coils as well. And maybe my MSD wires are defective?

 

misfires can be really annoying to track down. I'd swap in some oem wires and coils along with the new plugs. Also you might want to buy some new o2's, I know their expensive(i've gone through 3 sets) but they've helped every time.

 

Im only going to make 1 change at a time, that will help me determine exactly what is wrong.

 

im going threw the same problem and ive put in new plugs im running those msd wires 2 wonder if thats the problem i pulled one of my 02s and cleaned it and it seemed to deff help but im doing long tubes on monday so it will be all coming apart

 

maybe I need to look into new o2s? I dont see how that could be causing knock though.

 

my truck does this sometimes also, with the ac on

 

If the sensors were faulty then they would be giving the pcm faulty info therefore causing it to give bad mixtures.

I have some crazy issues that are similar but a tad more drastic. I haven't went inside yet, but I am pretty sure mine is a stretched timing chain or it skipped a tooth or something. Mine idles fine. You just can't give it too much gas (over 60%)

 

Is your AC bump spark on? I disabled mine as I was having a similar issue. Too much timing will cause your truck to "kick back" a bit. Try turning it off and report back