Toyota-Lexus-Subaru-Honda Carbon Buildup in Combustion Chambers Carbon Buildup

A small amount of carbon build-up in the combustion chambers is a normal byproduct of burning hydrocarbon fuels.
Excessive amounts of carbon in the combustion chambers take up space and can increase the compression pressures to the point that the engine starts pinging under certain conditions-usually conditions involving fully a warm engine, hot weather, and some level of accelerating.

Excessive oil burning can lead to carbon buildup. Chronic low rpm driving can also lead to increased carbon buildup. We had a customer that had a truck that had a chronic pinging problem, despite the fact that his EGR (exhaust gas recirculation) system worked, his timing had been retarded to decrease the tendency to ping, decarboning treatment had been run through the engine, he didn’t burn oil, and he used the 92 octane fuel.

This guy pussyfooted around at low rpm’s, always upshifting into higher gears early. His girlfriend had an identical truck that she drove aggressively and had no pinging issues. This guy took a trip across the country that required his crossing the Rocky Mountains twice, with a lot of sustained wider throttle opening than was his normal practice. The sustained heavier demands on the engine had apparently burned out the carbon, because when he got back, we were able to put his timing back to full advance, and he was able to use regular 87 octane gas without any pinging.