GMCtrk

iTrader: (27)

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?

dlt76028

iTrader: (13)

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

GMCtrk

iTrader: (27)

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

dlt76028

iTrader: (13)

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.

GMCtrk

iTrader: (27)

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

droppedchev

iTrader: (5)

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

GMCtrk

iTrader: (27)

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

JoeGibbSilverado

iTrader: (9)

my truck does this sometimes also, with the ac on

dewmanshu

iTrader: (4)

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%)

hirdlej

iTrader: (31)

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