Originally Posted by scwerks
my brother has a '02 4cyl. that developed the same symptoms. he keep on driving it while trying to diagnose the problems. the misfire would jump from cyl. 1 to 4 randomly and the engine shaking got worse over time.
at the time the motor had like 245k miles so our last assumption was that it had a burnt valve. finally he had a mechanic friend look at it and he came to the same conclusion. at this point, instead of just replacing the valve, my brother decided to just rebuild the motor so the heads went off to the machine shop.
it purrs like a kitten now and it seems to have more pep. hopefully, your situation isn't like his. you can start with replacing the plugs. swap the coils around and see if the misfiring moves to another cyl.
If it is misfires too long, you'll burn a valve and bend it.
and lose compression
old motor read like
Easy check is swap coilpacks around, clear code, drive it.
Scan codes, if it jumps a cylinder, it's 100% a coilpack.
Also, look into flowing your injectors..mine old 2RZ was missing because of coilpack plus also injectors weren't flowing correctly...there like $15-30 each to have them rebuilt with new baskets, o-rings and flowed.