Any ideas on what to check? It's been a problem since I've owned the car. I've tried every different brand of gas I can find, all with the same result; pinging under heavy load, mostly at low rpm but sometimes even at mid-range rpm (3000 - 4000). On one occasion I can recall, I had 3 passengers in the car on the freeway and accelerating up an incline from about 55 mph it started pinging.

I've pulled the plugs and inspected the combustion chambers as best I could but did not see any abnormal or excessive carbon buildup that might cause preignition. I've also checked the timing with a strobe and it seems to be within spec. I did have to replace the Engine Control Module at one point because it died, but the problem was there both before and after replacing the ECM.

As I recall, it calls for either 92 or 93 octane fuel, so 91 might be enough to make it ping, especially with the reformulated Calif. gas.

Is there a possiblilty that the fuel mixture may be too lean? Is there an accurate DIY way to check it?

Gary