When you say the rough idle is back, do you mean the same symptoms you had before replacing the pick up coil, cap and rotor, or do you mean the idle issue you were referring to in post 27?

 

The same symptoms before replacing the cap, rotor, and sensor.

 

If it wasn't a Mopar sensor, that might be causing problems.


With that many miles on it, I would be tempted to check the ignition coil out for cracks and resistance numbers. That could be giving you random misfires too.

 

The sensor is not Mopar, but I'm not sure if that is it. The coil does not appear cracked, and the multimeter gave me good numbers, but I did notice it is missing a mounting bolt. I grabbed it and tried to move it, but it is on there solid.

The p0300 code is consistent, and the same three cyclinders (2, 3, and 4) have been coming up with that code too. Sometimes 5 comes up, and 8 came up a while ago but hasn't returned.

 

Okay, so last night whilst tinkering I decided to unplug the injector of cylinder 3 while it was running. Absolutely zero change. I repeated this for the other cylinders, and C2 was similar while C1 and C4 made a slight difference, but not as much as when I unplugged C7 which has never shot a code. Where should I start? Fuel or spark?

 

Spark is easier.....

 

So I verified it was getting spark, and I swapped the injector, and it still changed nothing.

 

Get a noid light from the parts store. Verify you are getting injector pulse.

 

I used a multimeter while it was running and tested the pins, and it read 12.7 volts.

 

Digital multimeter doesn't react fast enough. You NEED a noid light. Consider, the injector pulse with is measured in milli-seconds..... and the PCM controls the the ground side of the circuit. With the engine running, there should always be 12 volts on one side of the connector. (and putting the other probe to ground.) If you measure across the wires on the connector, you might be able to read pulse with an analog meter... (the needle should bounce when the injector is 'on'....) but, it's such a tiny interval.... You may see nothing at all, or what the meter would interpret as a 'constant' signal. The noid light will blink. That's what its designed for.