Ok, here it goes. I have an 01 G3500 van-auto trans 5.7L

The problem I am having is when there is a sufficient load on the engine and at about 1750-1800 RPM the engine sounds like it is pinging or out of time. I can turn the distributor counterclockwise(I think this advances it???) and the problem will resolve itself somewhat but not quite.

Does the cam sensor just tell when the number one cylinder is on compression or does it also serve as an input to tell the computer when RPM's are high and then computer tells the ignition module to advance itself? Is this how it works or am I completely off track? So I guess what I'm saying is that it sounds and runs as though it is not adancing.

Any help would be appreciated.

The computer gets its RPM signal from the distributor. In this case, based on the symptoms, you might want to verify EGR function.

Thanks for the help. Got it fixed. I replaced the cap and rotor. There was a huge amount of corrosion on both of them. After the fact I found a tsb relating to this. It says to remove the 2 vent screens in the distributor to keep this from happening again. I did this too, they were clogged and I guess moisture built up inside.

Thanks for posting the fix back.