2003 toyota avalon 3.0 v6 166k miles backfiring though intake while running, rpm is surging from 500rpm to 1300rpm, and random misfire, live data stated 1 to 2 counts on cylinders 5 and 3 every 20seconds of idling, timing seems ok and in time, fuel injectors seem ok, and spark plugs were replaced, no codes, short term fuel trims were 5 %to 8% injectors were 4 to 5 milliseconds and o2 sensor upstream were around 0v to 2v, iac was replaced as well, all started after engine was revved high during traffic, timing belt was replaced and cam sensor was replaced, no air leaks,
Well if it was arrived too high, I'm assuming the damaged engine. Start by doing a compression test of all cylinders to see what shape the engine is in. I would also do my video how to tell if your head gasket is blown. Scotty. Start there
@scottykilmer performed a compression test and cylinder 1 was 200psi Cylinder 2 was 195psi Cylinder 3 was 165psi and adding oil brought it up to 195 Cylinder 4 was 195psi Cylinder 5 was 190psi And cylinder 6 was 180psi Manuel states tolerable compression difference will be 14psi and 2 cylinders were way more