My problem is a recent development. Last week my engine started missing every once in a while when I had the engine under load and the idle is a little rough. I checked it out that night and could see electricity around my spark plug wires on the 1 3 5 side. I got them replaced, along with the dist cap, rotor, plugs, and pcv valve. The miss is totally gone now, and so is the rough idle when the engine is cold. After the engine is at normal operating temperatures the idle gets rough, and the dollar bill test on the exhaust reveals that one cylinder isn't sealing fully. After the engine has cooled, even mostly, the rough idle is gone, and the 4runner passes the $ bill test. Sound like a burnt valve or is it timing issue?

Is there anything that I can do to prevent this from happening? Seafoam or equivalent? I don't have the time or money to tear down the head right now.

Any help, advice, or positive, constructive comments are greatly appreciated.

92 4runner, 3.0L, 5 speed, almost 202,000 miles

 

Had a simular problem several years ago (not on a Toyota) and it turned out to be a hairline crack in the valve face that would only open up and cause the rough idle when it was warmed up. Another thing to check would be the coil.

 

The coil wouldn't make the dollar bill suck back onto the exhaust pipe though. Thanks for the reply though. I hope it at least will last a while. Doesn't seem to be a loss of power. Only the rough idle.