misfire/idle high

Do you mean P0300? P0300 - Engine Misfire Detected I don't see any error codes referring to misfire with cly 1-4. Is this the only error you get? Have you had any major work done, such as relaced the PCM or crankshaft? If the PCM or crankshaft is replaced, the the crankshaft must be relearnd. Have you tested the spark plug wires? resistance should be between 1.5k-15k ohms. try replacing spark plugs and wires, if error still occurs, try replacing coil packs Try checking for vacuum leaks, often causes a high idle.

Thats all i can think of now. hope that helps

Jeremiah

Thanks!..P301 and P507 possibly just the way my reader deciphers them and it's just a general misfire but the OBD P code chart says P301 is a number 1 cylinder misfire.........Changed the wires and plugs, even did the resistance test on the wires and all good. Looks like coils are next. For past few days the weather has been hot and muggy and the idle has been around 800 rpms. This morning it's very cool and dry and the idle was at

1500 rpms again.

800 RPM is ok, the spec is 750 +/- 50. Could be your IAC Valve (Idle Air Control Valve), This controls your throttle plate opening at idle. If you have a Haynes book it's page 4-11 section 15. So if you want to start cheap, i'm sure a iac valve is cheaper then 2 coil packs. Also, just a though, your plug wires are routed the same way as stock right? I know this will cause some strange problems if the wires arn't done right.

Hoped that helped Good Luck

Jeremiah

Yep the wire routing is the same. Guess I'll try the IAC valve. Thanks!

Mis-fires are detected by measuring the rate of change of the crankshaft speed. If the cranshaft doesn't speed up enough after the cylinder has supposedly fired, then the computer records this as a mis-fire. This means that you can't just look at ignition problems. A misfire can be caused by an the injector that isn't supplying enough fuel, or a leaky valve, or whatever reduces a particular cylinders performance relative to the other cylinders. I spent 3 months trying to clear a mis-fire condition on my SO's van. We changed plugs, plug wires, distributor caps, etc. Turned out the problem was a burned exhaust valve on the offending cylinder. The vehicle always seemed to run OK, but it would set a mis-fire code with days of clearing the code after a repair (even the local Chrysler dealer kept trying to blame the ignition system).

Regards,

Ed White

snuffy wrote:

I was wondering how it detects a misfire. There are no sensors on the wires for sure. Probably should do a compression test and see if number 1 cylinder is low. Oil consumption jumped all at once also. Though it shows no oil fouling on any plugs. Very good info! Thanks much!