I have a 99 Cherokee its been giving me issues for some time now. It idles really rough and when driving it will randomly miss hard even back fire at times. I have replaced everything I can think of other then pcm, all oem jeep/Chrysler parts iac, tps, map, crank shaft position sensor, pick up coil, fuel pump, ect. I'm sure I'm missing something, I've gone through all the vacuum lines one by one, pulled the injectors checked all O rings... Checked all electrical connectors. I keep getting the same codes for crank shaft position sensor and iac. I took the rig to a shop had a computer put on it and and the computer says the same thing both are brand new oem parts. Is it possible the pcm could cause this problem and create these codes because they are getting a bad reading from the pcm? Please any info or help... I'm at the end of my rope and the bottom of my wallet.

 

Check related wire harnesses for wear. Coil on plug I think - maybe one of the coils is shot.

 

Single coil, spark plugs are new, wires maybe 6 months old, wiring harness and connectors have all been gone through...

 

I would check a sensor bro. Backfire I would probably check the 02 sensors. And\or the exhaust. Definitely either a sensor or possibly a fuel issue?

 

Double check spark plug wire resistance w Ohm meter - even new wires can be bad. And confirm routing of course.

 

O2 sensors also just been replaced... Could a plugged cat cause the issue?

 

I have not put an ohm meter on the plug wires I will try that, thank you

 

Compression check? How many miles on this engine?

 

I have not done a compression test, 102k miles

 

What are the exact codes?

 

That's not many miles for a bad cylinder. I was thinking it may be mechanical since you've replaced nearly everything else.
I had a '90 Mitsubishi that had similar problem. I replaced a lot of electrical parts but it was finally solved with a new computer. There were some capacitors that were leaking.