EGR valve and pinging

[Hugemoth]

Over the last few weeks I've noticed my engine pinging more and more. I put the timing back to 5 degrees from 8 degrees where I had it set but the pinging didn't stop. Thought maybe I got some bad quality (low octane) gas but a fill up at a different station made no difference. Finally got fed up with it this morning so I went out and put vacuum directly to the EGR valve and could see the diaphragm move freely but it barely slowed the engine at idle. Looks like it's clogged again.

About 25,000 miles ago I cleaned the passages in the head, the manifolds, and the valve itself. It worked fine after that and would kill the engine at idle. Since then I had some of the valve seals go bad which caused some oil burning and smoke particularly while decelerating. I fixed that problem but am thinking that the oil burning caused the passageways to become clogged with soot.

Tonight or tomorrow morning I'll clean the EGR system and see if that takes care of the pinging problem. I'll report back.

Q

[RossT]

In the factory service manual, under pinging, you will see that "excess oil entering the combustion chamber" is one of the causes of pinging. I had a geo last year that drove me nuts with pinging. I did everything: egr port cleaning, timing adjust, piston soak, seafoam, and final water mist cleaning. Turned ot the pinging was from to much oil in the combustion chamber.

[Hugemoth]

Cleaning the EGR valve seems to have taken care of the pinging problem. The passages in the head and manifolds were OK, it was just the valve that was clogged. Only took a few minutes to fix. Amazing what a difference a clogged EGR valve makes.

Q