Engine Performance problem
1999 Chevy Silverado V8 Four Wheel Drive Automatic 134000 miles
Well, bought this truck, running wonderfully with about 123k miles, decided to do a routine tune-up.
Installed ACDelco iridium plugs, gapped to.60 but later found out they were factory gapped to.40, so fixed that. Installed new air filter, fuel filter, autolite wires.
Roughly a week later my engine light came on, and went off, then a week more and it stays on. First it was bank 1, then both days later. Same 2 codes every time 171, 174 lean both banks.
Since the code has appeared, we have inspected vacuum lines, ran fuel pressure checks, 54-55psi key on, 55-60 under load, drops momentarily below 54 from dead throttle drop. Cleaned and inspected most sensors, installed a new intake gasket torqued per GM specs, inspected FPR, clean, Pulled EGR, cleaned surfaces, inspected operation, replaced gasket. Replaced MAF with rebuilt. Scantools show the MAF and O2's working correctly.
I can clear the codes, and the pendings pop up roughly 3 minutes into an idle, with the light comming on soon after.
Not long after the codes stuck, I started noticing a miss under load, usually after the truck was warm and driving steady around 30 minutes. Pulled plugs, found a crack in the upper porcelain of cylinder 2, replaced with old plug I removed, week later it cracked also. Crack begins about 1/16" down from the top of insulator and stops about 1/4" from the bottom. The old plug I re-installed cracked twice, same spot, about a mm away from the 1st crack.
It's no doubt that this crack is what's causing the miss, but what's causing it to crack?
Also, any ideas on where I can go with the lean codes. I want to take it to a dealer, but if I can try something myself that I haven't already, I will.
I am driving myself crazy working on this thing. It's still new to me, so I have to get it back to working correctly. Any suggestions are appreciated!
Friday, January 22nd, 2010 AT 10:32 PM