Hi all- I just bought this 91 jeep xj sport, 5 spd, with 131xxx miles. It's straight and runs great! However, in 1st gear, on rough road it bucks. I've debated whether it's me or not..but I'll share my experience, and you tell me.

When engaging the clutch and going into first gear, if there is a bump in the road, or coming out of a parking lot where the exit is rough or bumpy the jeep bucks. Quickly putting it in 2nd puts an end to it. Yesterday while at my favorite fishing hole, in 1st gear driving over bumpy rough terrain (gravel) it was bucking - it seems like the gas pedal is ultra sensitive.

I've searched this topic and from what I've read it could be the o2 sensor, or a bad fuel pump. Oh, and the check engine light is on.

The only difference I could find, or what I did not see others relate to bucking was rough terrain in 1st gear. So, I thought I'd add one more "bucking" thread.

Thanks in advance.

 

inspect the motor mounts

 

First thing you should do is see what codes are coming up. That would give you some place to start looking.

 

Okay, I pulled obdl (91 xj) codes twice, and they are...

12 - recent battery disconnect (within last 50 starts)
33 - air con clutch relay
35 - cooling fan relay

This jeep does not have air con, so why would I get a 33?

I don't know, but these don't sound related to the issues I'm having.

 

"This jeep does not have air con, so why would I get a 33?"
Probably because the a/c circuit is open.
Rough running sounds like an electrical (ground) issue.

 

I had a similar problem when hitting bumps on the road. It felt like the car wanted to shut off. Turns out I had a bad CPS. Once I changed it, it ran like a champ again.

 

Jeep runs great. Idle does have a little tremble though- only bucks in 1st gear.

 

check the ground for the injectors. mine was doing the same thing