Mr

[Digger857]

I have a 2000 Silverado 5.3.  I am having “service engine” light chaos. The truck has 300000 miles and runs like a sewing machine. I’ve had it since new. The light comes on when idling. Sometimes the code is “multiple random cylinder misfire”. Sometimes it’s “system too lean bank 1”. I have replaced the plugs twice, the wires twice, the coils twice and the injectors once. If I continue to idle, the light starts flashing. I turn the light off and drive as far as I want, problem free. Until I idle for any length of time. I have taken it to two garages and the dealership. Nobody knows.  Help!

[davester]

check the exhaust manifolds for broken off bolts (this can cause an exhaust leak where it sucks clean air into the exhaust, making the O2 sensors read lean).

 

How did the plugs look that you took out?

[mjm-1957]

I would replace the intake gaskets and while your in there replace both knock sensors and the wiring harness.

[riverbanks]

Has a cat converters back pressure test been performed?timing chain slop test?swap 02's side to side,see if bank 1,turns into bank 2 lean? crankshaft relearn procedure been done?