toomanytoy

My wife's 05RX has just turned 74k miles on it and recently I've noticed the motor has detonation at light throttle. If I press a little harder on the gas it goes away. Ive tried getting gas from different stations with no change. Anyone else have this problem? The car isn't running rough or missing and there aren't any fault codes. A little help here would be great

fastnoypi

detonation would typically give misfire CEL codes. Is it making a noise? If so can you isolate it to an area of the engine? You didn't specify what octane you are running. Can you replicate the "detonation" with 91 or higher?

racer24

Are you sure it is "detonation?" I would expect the knocking and pinging would get worse with more throttle and more load; like going up a hill. With today's computers and knock sensors, detonation is pretty rare. Are you burning any oil? Do you get a puff of blue smoke in the morning when you first start it up? That could be an indication of worn valve stem seals which could cause some spark plug fouling and effectively lowers octane. I would look for a new "rattle" in the engine compartment.

toomanytoy

It doesn't burn or leak any oil and it is definitely detonation. My wife always uses 87 octane regular.

fastnoypi

try a tank of 91 and see if it eliminates it. Detonation shouldnt happen at low loads. The car's ecu will compensate up to a certain amount by pulling timing to avoid knock. You can also disconnect your battery temporarily to reset the ecu's learned knock.