misfire/idle high

My 2002 sc1, 1.9L, sohc, always shows the same codes. Cylinder #1 misfire
and idle higher than should be. Any ideas?

 

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

 

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!