P0300 code on a 1998 Cherokee Classic with a 4.0 I6

My sons 4.0 is throwing a P0300 code and spitting and sputtering like crazy. After looking it up I see that it means that it is a multiple cylinder misfire which is exactly what it feels like. The first ( and cheapest ) thing I thought of was maybe a cracked distributor cap because he said it happened right after hitting a pot hole ( That has happened to me before ), but the cap seems to be okay.

The next thing I thought was the coil. Thankfully this one doesn't have the long coil pack that the later 4.0's do, it is just the little square pack with the one coil wire coming off of it. It is cheap enough to replace, but I don't want to just start throwing parts at it either you know?

It's also throwing a transmission code that it has never thrown before, so I am assuming it has to do with the P0300 code and the engine not building enough pressure for the tranny.

So, I'm throwing this out there to the Jeep Guru's, what do you guys think?

Thanks in advance!
Thomas

 

Check out the video in this other thread: https://www.jeeps.net/threads/check-engine-light.142/#post-763

 

Thanks for the link to the video. The guy in the video is great! He gets right to the point and doesn't mess around like a lot of the other guys.

We did new plugs, wires and battery when we did the top end rebuild, but I pulled the cap and the tips are grooved, so I'm going to replace the cap and rotor.

A local Jeep Guru came by and looked at it and he said he had a guy that had the exact same thing happen to his Jeep and it was his throttle positioning sensor. That makes a lot of sense too being an electrical piece since we all know how electrical pieces are and it started after he hit a pot hole.

I'll pick them all up and replace the cap and rotor first, if it is still doing it, I'll go ahead and put the sensor in. if that doesn't fix it. I'll know it isn't the sensor and take that $50.00 part back! LOL


Thanks a lot!!