88 xj rough idle

[fuzzy]

Jeep has rough idle bit runs fine going down the road .. any help will be appreciated

 

[milspecmechanic]

Spark plugs clean? fowled? properly gapped? pull each spark plug wire one at a time and see if it sounds better or worse. if it sounds worse, everything is good there. if you can't tell a difference, troubleshoot the cylinder from there. What engine do you have?

 

[fuzzy]

4.0 and thanks I'll try that this weekend

 

[88jeepster]

be glad to help man. that renix model can be annoying to diagnose. the tps is adjustable and can cause that, the ground circuit for the tps should be checked and add an extra ground wire to that circuit, as other guy said check your basics first but if that doesn't solve start looking at the two mentioned above. adjusting tps on Renix jeeps is huge importance and lots of connections have corrosion in that big black connector at the firewall above master cylinder which cause voltage drops and grounding issues for harness running to tps. theres a whole thread for that connector issues but take it out and clean it real good with brake parts cleaner and then electric spray along with the ground strap at the back of the head, and then check ground voltage on the ground wire to tps. very common problems on the 87-89 XJ renix which I've owned 9 of them so been there, done that with tons of hours of figuring and researching. hope this helps, let me know if you need more direction. happy wrenchin!

 

[xjtrailrider]

Check and clean all of your grounds. there is a strap from the rear of the head to the cowl and there are 3 grounds that attach to the stud at the dipstick tube hold down bolt.

If you are sure all of those are good then adjust the TPS according to the RENIX FI FSM. Also the small vacuum line going from the TB to the MAP needs to be in perfect condition. If there is any loss of vacuum going to the MAP it will not run right.

Cruiser54's RENIX troubleshooting thread from NAXJA;http://www.naxja.org/forum/showthread.php?t=1072534&highlight=cruiser