This is a very strange issue. 1997 3.4L SR5. It all started with a single #3 misfire. I found I had a failed head gasket at #3 cylinder. I pulled the heads and confirmed the gasket had rotted away. The engine has 100k on it so I changed the t belt and all that stuff at the same time along with both head gaskets. It seemed to run ok but still had a little rough idle at times. After a few days the temp started to climb and found out the radiator was plugged. New radiator and no more temp problems. Now I will get a random misfire code if I let it idle at warm up for a few minutes. All cylinders show up with misfires except #6. The engine runs great off idle, no misfires, surges or any issues and the fuel mileage is normal (20 mpg). I watch it all the time. The plugs are new and all injector seals were changed. I have checked for vacuum leaks but found none. The 02 sensors have been changed and fuel filter in the last year. After a run on the freeway I can pull up to a stop and it will run smooth for a few and than just start to idle a little rough. Hit the gas a she runs perfect. Is it possible to be off a tooth on 1 cam and still run this good? Everything seemed to be right. I pulled the plugs and they look like new. Can injectors cause this?
I have rechecked the timing marks and they look perfect. It will run for a week without a light coming on and only run a little rough at a stop light in gear. Rechecked for vacuum leaks. None found. No overheat issues at all even in hot weather with A/C on. Even if it was an ignition problem you would think it would be worse under load. Not the case.
Linear Mode
