A quick backstory to my Jeep, I bought this from a person who stated the transmission was out, it couldn't go in gear, and it was not driveable. I had a buddy haul it back to the house and we started to mess with it and found that the T case was needing to be rebuilt. So, I rebuilt it and it is back to driving. The motor was always able to be started. The battery was weak because she let it sit but I have since fully charged it and it will start right up. It has always had a rough idle but never had codes. I found a thread where @Jerry Bransford said to check your transmission fluid level. I did, I was down 2 quarts and that really helped with the idling. I also replaced the plugs with NGK ZFR5N. I took it out for a test drive and the check engine light started flashing and it was a dog getting back up a long hill going home. That's when it showed P0300.
I installed all 4 O2 sensors with NGK sensors as per the O2 sensor thread on here by @Chris hoping it would help but I still have a rough idle.
My symptoms are:
Rough idle but smoother when in Park or Neutral
The throttle seems to be responsive and makes the rough idle go away
It looses power when I get up to speed on our county road
I can clear the code but it does come back when I'm up to speed on the county road
Specs:
2002, 4.0, auto 3 sp, 175k miles
I installed all 4 O2 sensors with NGK sensors as per the O2 sensor thread on here by @Chris hoping it would help but I still have a rough idle.
My symptoms are:
Rough idle but smoother when in Park or Neutral
The throttle seems to be responsive and makes the rough idle go away
It looses power when I get up to speed on our county road
I can clear the code but it does come back when I'm up to speed on the county road
Specs:
2002, 4.0, auto 3 sp, 175k miles