97 SL320 running rough
 

I checked the codes and I'm getting P300 random misfire its idling rough I changed the spark plug wires and plugs its still running rough Is there a way to check the coils without replacing them all to see if one of them or more is bad? or is there another likely cause?

Thanks for any suggestions or insight

Steve in Reno, NV

No coil tests that I could find.

But your car has individual coil packs, correct? If a coil was the problem, you would (probably) get a 301 to 306 for the particular cylinder.

I would take a close look at the wiring harness' insulation, although this was supposed to be fixed by '97. I would check carefully for vacuum leaks. And see what the oxygen sensors' and adaption readings were saying.

Beyond that you would need the full diagnostic system to pinpoint the problem.

And you replaced the spark plug connectors?

Wire Harness?
 

Yes I changed the wires and the contectors on the coils I'm leaning towards the wire harrness although I dont see anything wrong with it. I did have my instrument panel go crazy before this stared my clock was going in circles and other gauges reading crazy.

Thanks
Steve

Here's a nice related article - http://www.obdii.com/articles/Engine_Misfire_UC.html