Howdy. Been having a problem with my 2002 SL2 SOHC, getting two error codes P0301 cylinder 1 misfire, and P0507 Idle Control system, RPM high. Doing the ignorant thing, I changed the sparkplugs, plug wires and the IAC valve. Didn't help. The engine idles at a minimum of 1500 rpm's cold and 2000-2500 rpm's warmed up. When approaching a stop, stepping on the clutch causes the rpm's to spike about 500 rpm's, and drops in about 5 seconds. While driving it I'm not noticing a loss of power or sluggishness. When at idle, I do notice a mild shaking in the engine, probably cylinder 1 still misfiring. There is an above normal temperature (on the dashboard) reading when not moving--but that's just probably the higher idle.


Any ideas on where to look next, smog check is this month. Edited by: sw2cam

This was a sucked in fiber gasket on the air intake manifold, causing both the IAC valve code and the cylinder 1 misfire.


Took it to a mechanic and it runs normal again. If you have an IAC error code: P0507 RPM too high, along with a cylinder misfire code(s), you may want to check out the gasket.
Edited by: sw2cam