fillupread

Hey guys and gals,,,, New here and need some help.

I have spend years working for GM as a Tech and my own truck has got me stumped! I could use some help.

2002 Silverado 2wd half ton with the 5.3. 150000 miles.

The engine spark knocks light to heavy, gets real heavy after 3000 rpm.. The knock retards the timing but I can feel the truck hunting for timing before the knock becomes severe. I have a huge loss of power when this happens. If I drive it light it isnt a problem but I can feel it. If I drive medium to heavy it knocks like mad causing the timing issue. I cannot tell if it is a timing issue causing the knock or knock causing the timing issue.

It isnt consistant either. Some times it will run up to 4000rpm and then start its problem. Some times it will start around 2000.

If I push it during the knock the CEL will flash but not set a hard code. I will find a P300 random cyl misfire soft code. It has not set anyother code. When it sets the misfire code, it sets 2 of them each time.

It only does this under load. I find nothing wrong at idle.

What I have done so far:

Last winter I installed a new intake gasket because the original was sucking air when cold. Typical problem. The engine ran fine before the intake gasket and fine for a year afterward.

For this problem I installed a new rear Knock Sensor. I found the Knock Sensor TSB and the description sounded similar to what I was having.

New fuel filter has been installed.

Fuel pressure is 50 psi at idle.

(update. I installed a new fuel pump and it still reads 50 psi. Guess I need to calibrate my fuel pressure gauge!)

Original plugs were replaced with factory replacements at 100,000k




HELP!

ZX1100F1

The first thing (most common) to check for is a pin that has backed out in the main engine wire harness connector, this is the large connector under the hood with the locking lever.