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99 High Idle

X

XJ Coyote

NAXJA Forum User
Location
Newport Beach, CA
99 xj sport, 4.0l, AX-15, NP231
My '99 has started to idle high, I have searched a ton and found a lot on this problem, but it seems most of the threads I find are associated with the earlier Renix engines. So I am just wondering if the common problems, ie. vacuum leak, dirty IAC, etc. is still applicable to my engine.:dunno: Thanks
Coyote
 
XJ Coyote said:
99 xj sport, 4.0l, AX-15, NP231
My '99 has started to idle high, I have searched a ton and found a lot on this problem, but it seems most of the threads I find are associated with the earlier Renix engines. So I am just wondering if the common problems, ie. vacuum leak, dirty IAC, etc. is still applicable to my engine.:dunno: Thanks
Coyote
Click to expand...

Does it consistantly idle high?

Vacuum hose, intake manifold, throttle body, leak is a major possibilty for any modern vehicle, not just jeeps, and not just renix jeeps. TPS is a possibility, and I think ground problems are still a possible issue even with the newer jeeps. And yes a sticking IAC is also possible.
 
It isnt really consistant, if it is idling high, i can turn the car off at a light and turn it back on and its fine, but sometimes it will come back after a few minutes. It has just started doing this. im gonna check all my bolts and gaskets and clean the t-body and iac today, thanks for the help
 
In that case it could be the TPS sensor going bad.
 
ok i just went to move the thing into the garage and it wont stay on. it starts and then as soon as it fires it dies. if i throttle it it will keep running, but putter out as soon as i let of, even if i let it down real slow to like 500 rpm, it dies.
I think ur right about the TPS....
 
Ecomike said:
In that case it could be the TPS sensor going bad.
Click to expand...

X2. My 99 also did the same high idle (idle was about 1000-1100 rpm) sporadicaly, it also would come in and out of OD while cruising down the highway. A new TPS solved both.
 
Just put it in. You can't adjust the TPS on a non renix 4.0. However on mine, there was a consistent high idle when it first cranked it up with the new TPS. I had to take it out and drive it a few miles, and shut it down and restart it a few times for it to smooth out. My guess is it was adjusting on its own.

How many miles are on your engine?
 
If it's still on the OEM TPS, it's time for one anyways.

While you've got atleast one sensor off, I would pull the throttle body out, and disconnect the rest of the sensors from it, and give it a good cleaning. Be careful not to get throttle body cleaner in the areas where your sensors get plugged in, as it probably will mess them up.
 
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