Jeepster She Runs

[dgoodenow]

Thanks. It has the Zenith PN 647572. It runs at idle but misses sometimes (coughs) but there is no backfire. I tried to adjust the idle mixture screw and it will only cause the engine to falter when almost completely turned in. Turning it out does not affect the engine at all, or at least very little.

[bmorgil]

The idle mixture screw does not make dramatic changes when turned out. If it is making a difference it's working. If it will stall it out when turned in it is definitely working. To adjust the idle mixture turn the screw in until the engine RPM's start to drop or the engine starts to stumble, then turn the screw out until it reaches the highest RPM and stop there. You are trying to find the spot where it runs the best at the highest RPM, screwed in as far as you can.

Misfires while idling are almost always traced back to some type of ignition issue or a burnt and/or out of adjustment valve. Fouling plugs, wires, dirty points or weak coil among a few things. If it is running well down the road at a light load, I would look into the ignition components. Igniting the mixture at idle and under load requires a good spark.