--UPDATE--

Just got a call from the machine shop.
After examining the heads the following was found.
NO CRACKS!
Valves pitted badly.
Cylinder 4 exhaust valve bent from striking piston after rocker broke.
Solution,
Replace all valves.
Replace valve seats with new spiral seats.
Replace springs.
Grand total,
$375.00 total for both heads.

Outcome: HAPPY!

 

Well problem solved.... This is what caused my headaches... Along with the stupid rocker and bad spider.
I think the injector may have caused all this damage.
Now I have to wait a week for my new roller rockers to come in!

 

Ok, so after 2 months of being down she is alive, New spider, new coil, new plugs new wires, "new" entire top end, new cats, and new O2 sensors!
New PROBLEM!!!!!!!!!!! An outright blatant misfire of cylinder 2!!!!!!!!
I am now at my wits end.... Anyone who can help... please help! I am going insane here!

 

ok new symptom... popping through the upper air intake aka plenum.....
I may have gotten ahold of a bad spider injector?

 

Ok problem solved! Bad injector at cyl 2


Now why am I running lean?
LT FT Bank 1 and 2 at idle well within the -10% to +10%
Under load = 14% + and up on both banks.
O2 bank 1 = .1-.4 volts O2 bank 2 = .1-.4 volts....

Will be checking vacuum for leaks tonight. Do not think it will do any good as I have replaced all Vacuum lines when top end of engine was being rebuilt.

 

Finally after nearly 3 months!
It is alive!
Went from 12 MPG to 16 MPG...
Now it passes everything on the road.... well except the gas stations....
Now if only I would be able to tweak it to 18-20 MPG!

 

Man you hae had quite a run to get this thing on the road again. I have mine sitting at the moment. Havent driven it a mile since I got it. 2 codes on it. Random misfire and tranny slipping. Hopefully it won't be as drawn out as yours, but at least I know where to look if the tune up doesn't work. I'm glad to hear you are on the road again. Congrats.

 

my 02 envoy did the same thing. the plastic filler tube cracked at the tank and had to replace the tank. when it rains it pours!