'91' XJ: fluctuating idle when at stop, in gear

The idle in my '91' XJ has been fluctuating by 500 RPM when I'm stopped in
gear (auto trans). If I put the truck in neutral the idle
fluctuation disappears. The auto-trans shifts fine and I recently (within
the last year) refilled the auto trans fluid 4 times (to get out as much of
the old fluid as possible) w/synthetic auto-trans fluid. Am I looking at
serious problems here?

--
Remove nospam to email

Doug did pass the time by typing:
> The idle in my '91' XJ has been fluctuating by 500 RPM when I'm stopped in
> gear (auto trans). If I put the truck in neutral the idle
> fluctuation disappears. The auto-trans shifts fine and I recently (within
> the last year) refilled the auto trans fluid 4 times (to get out as much of
> the old fluid as possible) w/synthetic auto-trans fluid. Am I looking at
> serious problems here?

Clean your throttle body.
http://members.cox.net/wilsond/tb/tb.html

A little fluctuation is normal, it's caused by either the alternator
or the AC compressor cycling.

--
DougW

Thanks Doug. I don't have to remove the throttle body to clean it do I?

--
Remove nospam to email
"DougW" > wrote in message
news:nwHYd.7252$ju.3812@okepread07...
> Doug did pass the time by typing:
>> The idle in my '91' XJ has been fluctuating by 500 RPM when I'm stopped
>> in
>> gear (auto trans). If I put the truck in neutral the idle
>> fluctuation disappears. The auto-trans shifts fine and I recently (within
>> the last year) refilled the auto trans fluid 4 times (to get out as much
>> of
>> the old fluid as possible) w/synthetic auto-trans fluid. Am I looking at
>> serious problems here?
>
> Clean your throttle body.
> http://members.cox.net/wilsond/tb/tb.html
>
> A little fluctuation is normal, it's caused by either the alternator
> or the AC compressor cycling.
>
> --
> DougW
>
>
>

Doug did pass the time by typing:
> Thanks Doug. I don't have to remove the throttle body to clean it do I?

Nope. Not unless the idle stepper motor is well and truly
clogged, then it's four torx screws to take the idle assembly off.

Just spray into the little slot and with the engine off, open
the butterfly all the way and scrub it and the sides of the TB
with a toothbrush and some cleaner.

All bolts/screws only go to a few inch.lbs so only use a driver
on them, never a ratchet, and only tighten snug, like your putting
a screw into soft metal (which you are).

Just remember if you do take the idle assembly off, do not pull
the pintle out, that's a "bad thing". Also don't run the engine
(or turn the engine on) with the stepper motor out and
connected, the pintle will go flying.


--
DougW

That sounds like a dirty connection on the TPS. It has a connection to
the tranny. The plug just gets dirty and can be cleaned with a spray
contact cleaner. WD40 will work.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Doug wrote:
>
> The idle in my '91' XJ has been fluctuating by 500 RPM when I'm stopped in
> gear (auto trans). If I put the truck in neutral the idle
> fluctuation disappears. The auto-trans shifts fine and I recently (within
> the last year) refilled the auto trans fluid 4 times (to get out as much of
> the old fluid as possible) w/synthetic auto-trans fluid. Am I looking at
> serious problems here?
>
> --
> Remove nospam to email