Hi, I just signed up and need some advice. I am borrowing a 98 YJ for awhile from a friend. ( Straight piped now because of bad muffler.) Ran better, so I changed cap and rotor this morning. Now it idles great, but in drive it sputters and backfires. This beast has 166k on clock, and most everything else functions. Any help is appreciated

 

First guess is mixed up plug wires.

 

Thanks for quick reply. I could have sworn they were all in proper spot. Will try again after work, glad I can walk to work. Have a great holiday weekend

 

Yup, plug wires would be my #1 guess too. If this backfire did not occur before the tuneup, it's related somehow to the tuneup parts you installed or how you installed them.

Good luck and keep us posted!

 

Good morning to all. I re-ran all the wires, and made sure none are grounding on block with separators. She idles just fine, revves up well in park and neutral. In drive, still get backfire over 20 mph. I did purchase standard cap and rotor instead of premium kit. May have to upgrade? Any other ideas? Thanks from La Vista, NE

 

2nd pair of hands and eyes helped!. Runs ok for about 15 minutes in normal traffic, then starts to pop and backfire. Will get scanned on Tuesday. Injector issue maybe?

 

Hi new Jeep friends! Sorry for late response, busy. "Olive" needed 2nd cap and rotor. Rotor contact came loose and chewed up cap, what a mess.
New issue! Found a front shaft so 4wd would work. Local shop had to cut and balance to fit. U-joints (3) all looked good and were not replaced. I feel vibration now up front, but diff. plug is stuck and haven't checked gear oil in diff. 80-90 if needed?
Could transfer case be an issue also, as old man winter is fast approaching the Nebraska area. Thanks for previous help, any new ideas?

 

I would still suspect the old u-joints. Since the shaft had to be resized, this means its previous application was operating at different position, however slight. The joints end up with a wear pattern for that application.
In the drive shafts new position, as the joints turn and encounter that wear, it will/can cause a vibration.

 

Thanks for the advice, once some extra $ roll in, I'll get new u-joints done. Have a great weekend, Carl