mtm1516

ok, I have a 99 sport 4.0. it runs fine, plenty of power, etc. the issue is my idle, its sort of rough. ive done a complete tune up, cleaned the throttle body. at this point, im sort of at a loss. if anyone has ANY ideas, im all ears!!! thanks.

tjwalker

Did your complete tuneup consist of fresh plugs (NOT BOSCH), wires, cap, rotor?

mtm1516

wires, cap, and button . i used champions, gapped to .035.

ken72

How long have you owned the XJ. Explain a sort of rough idle. What are you comparing the idle to. The way it idled a week ago a year ago or what? Mine has a slightly rough idle but I have learned that these jeeps are rough in every way. They are older and you will feel the idle a little more than you would in a new vehicle. Parts are just older. You might want to start looking at sensors. I have replaced my TPS, MAP, and IAC plus I have an O2 in the garage I plan on installing this weekend. Those helped my idle issues some. It still has a little rough idle but it seems to be common. Try running some lucas or seafoam fuel cleaner and see if your injectors need a little cleaning. Speaking of injectors, check your fuel rail and manifold for any injector leaks. You will know when you see one becuase the manifold around the injectors will look a little wet. These jeeps need a little more than plugs and TB cleaning for a tune up.

mtm1516

well... ive had it for 2mos. the "rough" idle is sorta smooth, and at the last second..a hiccup. its really odd. injectors maybe?

ken72

mine has gotten better with the replacement of the sensors I mentioned above. also what kind of gas are you using. Have you tried a different quality of gas recently? I have found my engine only likes Shell 89 and runs much better on that. Some people will call BS on this one. But I have tested all three and the 89 was what it ran best on.

thegoat2000

im in the same boat iv done lugs wires cap button seafoam took the tb off and took it all apart and tryed diff gas and grades and still a little rough

mtm1516

oddly enough, after i left work tonight, i romped on the beast a little bit. it seems to have smoothed out (for now). i appreciate your advice!!

kbad

hey man.... ditto TJWalker..... if you haven't yet, check your iac - you can try cleaning it with some tb cleaner/seafoam and it may be good for a while, but it's not too expensive and you can swap it yourself .... while at it, make sure your battery is nice and strong, always good to rule out battery/electrical at the very beginning.... good luck!