1997 Geo Tracker 1.6L v16 engine p0300 multiple misfires confirmed

Question

97 gen tracker v16 at start up eng. misfires and sets eng service light. Accelerating will stop erratic misfire and eng. runs smooth. going back to idle and same very rough idle. New plugs. new wires. new dist. cap new rotor. checked egr. no carbon buildup, checked throttle plate no carbon. I don't believe it is in the crank shaft, position monitor or the cam shaft position monitor, because it runs smooth at 2500 and higher rpm. No loose wires at the computer, or in the engine compartment. Just will not idle for sour grapes. I even checked at the throttle positon monitor, but at higher rpm everything is running smooth. What is the next thing to look at. I put some sea foam in fuel tank, just for drill, knowing full well it wouldn't help and it didn't. WHAT IS THE NEXT THING TO CHECK????????

Answer 1

Hi there

Check for vacuum leaks at idle. With the engine running spray some carb cleaner along the intake manifold and all the vacuum lines. If the idle speed increases or smooths out, this means you have a vacuum leak. If there isn't any vacuum leak, then I would check the timing. If the timing is off slightly it could have issues with the engine misfiring at idle. Once you hit 2500 you are basically rolling past the misfires most likely. It's probably still there, you just can't feel it.