Have you looked into the Idle Air Control (also known as the Idle Speed
Control). Its a device that regulates the air flow at idle to control the
idle speed. My '92 Dodge Caravan with the 3.0.l V6 has had similar symptoms
that were due to a sticking IAC. The IAC controls air flow around the
primary throttle and on this engine the dirt builds up inside the passages
such that the IAC valve sticks on ridge of hard dirt buildup. When it
sticks, the valve can't open properly as the engine goes to idle and the
engine dies as you pull to a stop. It will restart and will run if you keep
your foot on the throttle enough to keep some air flowing. The fix is to
remove the throttle body and the IAC assembly and clean the ridge from
inside. A faulty, rather than dirty, IAC would give the same symptoms.
On the 3.0l V-6s of this vintage, this is a well-known problem and a good
source of revenue for many Chrysler dealerships. It happens about every
30,000 miles on my minivan. If you're not familiar with the problem, it can
be very difficult to diagnose as there are no fault codes generated. A
friend had the fuel pump replaced and several visits to the mechanic before
they figured out what was going on. I found out by visiting a Chrysler
newsgroup.
Obviously this is a different engine, but you might look into the IAC/ISC
device on the 5.2 versus continuing to replace the TPS. If you are going to
buy TPSs you might start getting them at an aftermarket source. They're
generally much less than $100.
Vibration can cause rapid failure of TPSs. We had this problem on engines
we build for a big three customer when the TPS was mounted out on the end of
an unsupported arm. The vibration caused the TPSs to fail quickly, so you
might look into that as well.
Ben Zwissler
zwissler@hsonline.net
Columbus IN
----- Original Message -----
From: <Jeeptoys@aol.com>
To: <shop-talk@autox.team.net>
Sent: Sunday, November 26, 2000 3:09 PM
Subject: 93 Jeep GC idle problem
>
> I have a 93 Jeep Grand Cherokee 5.2 liter. I have had nothing but idle
> problems since purchasing it new. It has been to the dealer a number of
> times with little or no improvement. The engine will stumble and die at
low
> RPM, most often after initial start up when the engine if less than fully
> warmed up. Coming up to stops, the engine will die. Repeated starts will
> follow. I can nurse the throttle to keep the RPMs up above 500 - 600 and
the
> vehicle is drivable. When the vehicle slows (engine load decreases) the
RPMs
> drop and the engine stops.
>
> I have replaced the throttle position switch yearly since purchasing the
> vehicle. Most of the time the switch replacement will temporarily fix the
> problem for 6-12 months, then the idle problem returns. Testing the
suspect
> switches with a multimeter reveals few clues. Using contact cleaner on
the
> switch has no effect.
>
> Is anyone aware of this problem on other JGCs? I have a hard time
believing
> that the nearly $100 TPS from my friendly neighborhood Jeep dealer is of
such
> poor quality that it needs to be replaced every 6 - 12 months.
>
> How about it fellow listers, have any thoughts on the subject? Am I only
> treating the symptom of some other underlying problem? Any thoughts on
what
> may be causing the premature failure of the switch?
>
> Regards, Kevin
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