MJ Auto Tranny Issue - JeepForum.com
 
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post #1 of 12 Old 01-29-2005, 09:17 PM Thread Starter
97_4popper
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1990 MJ Comanche 
 
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MJ Auto Tranny Issue

Hey all.
My son has 90 Comanche that we are fixing up. 4.0 auto. AW4, I think.

The transmission intermittently shifts back and forth from 2nd, 3rd and OD when at a cruise speed. You'll be cruising down the highway in OD, then it will downshift to 3rd and then 2nd like you were flooring it. Then it will shift back to 3rd and OD. Back and forth. Sometimes it does it badly, sometimes works fine.
It seems that if it is doing it and you park somewhere, turn it off and then start back up, then the next time it won't be as bad.
New tranny needed... something simple?
Any ideas?

Help.

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post #2 of 12 Old 01-30-2005, 01:39 PM Thread Starter
97_4popper
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Somebody in another forum suggeted a TPS.
Anyone have any input?

Does the TPS have such control over the Auto?
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post #3 of 12 Old 01-30-2005, 02:26 PM
cj7xjmj
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It very well could be the TPS, or the computer in charge of the tranny. The AW4 is almost an indestructible tranny.



Patrick

90 Comanche thing. Exo-cage, tube bed, with a few other things done Here is a link to some pics of it
http://independent4x.com/generic67.html
http://community.webshots.com/user/cj7xjmj
If you have to ask why... Its a truggy thing and you wouldn't understand
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post #4 of 12 Old 01-30-2005, 05:46 PM
MSHarnett
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I agree that it can very well be the TPS or possible the MAP sensor. But, whatever it is, it deffinatly sounds like a sensor problem, the actually tranny should be fine.

I toasted my tranny with only 120k on the clock, so who knows

Matt
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post #5 of 12 Old 01-31-2005, 07:02 AM
cj7xjmj
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My mj Has well over 140 showing, and I have yet to have a tranny problem out of it(knocking on wood as I speak). So I don't think it is an internal problem on the tranny. TPS, Map, or maybe the Transmision control module, but not the tranny.



Patrick

90 Comanche thing. Exo-cage, tube bed, with a few other things done Here is a link to some pics of it
http://independent4x.com/generic67.html
http://community.webshots.com/user/cj7xjmj
If you have to ask why... Its a truggy thing and you wouldn't understand
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post #6 of 12 Old 01-31-2005, 05:40 PM
dadjlh
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I have indeed had the same problem, twice. First time it was the TPS. Second time the kick-down cable (called something else in book, can't recall) had slipped. Performed the simple abjustment called out in manual and it fixed the problem. Both times had same symptoms as yours.

1994 Grand Cherokee Limited (Silver)
4.0 I6 42RE
NP242
Dana30/Dana 35C 3:73

1988 Comanche Pioneer (Blue)
4.0 I6 AW-4 2WD
D35C Rear Axle
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post #7 of 12 Old 02-02-2005, 07:39 AM Thread Starter
97_4popper
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Thanks all.
I'll be looking into the TPS. . .
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post #8 of 12 Old 02-06-2005, 04:01 AM
badron
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Get some contact cleaner and spray the TPS wiring plug. As a mater of fact spay the plug to any sensor that is in question of being bad. Even gold ones. Then retest. A lot of good sensor have been replace because of a dirty plug.
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post #9 of 12 Old 02-06-2005, 08:35 PM Thread Starter
97_4popper
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Quote:
Originally Posted by badron
Get some contact cleaner and spray the TPS wiring plug. As a mater of fact spay the plug to any sensor that is in question of being bad. Even gold ones. Then retest. A lot of good sensor have been replace because of a dirty plug.
Folks,
Removed the throttle body that someone suggested.
Cleaned it and cleaned the contacts for the plugs.
2 days and so far so good.
My son is happy.

We'll see if that holds up. . .

Thanks to all!
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post #10 of 12 Old 02-14-2005, 09:50 AM
bockwho
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if yours also has the power comfort switch on the dash I have been told to keep it in power at all times by a guy that worked on them at a jeep dealer.

I was told this when I was explaing my wandering between gear problem with my MJ.

A tps can also be connected to a meter it should have smooth resistance ohm's

it will also be smooth to the touch you know when you dimmer gets old it breaks and you feel a little skip in it.

When you install a tps you should also get a value. at closed throttle on older 4.0 newer ones do not have a adjustment.

kelsey

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post #11 of 12 Old 02-14-2005, 10:10 PM
zcfd02
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Very similar symptoms

My 90 MJ 4x4 LB had developed a whistle, which only occured during coasting, and was shifting up and down between 30 and 55 MPH when cruising at a constant speed. No problem accelerating or decelerating.

Two mechanics and a tranny specialist were stumped - the advice, after draining my wallet somewhat - was to wait for it to get worse so maybe they could find it.

Heard about a shade tree tranny man - who lived and worked on cars at his home with a rep for honesty and "seen it all".

Started off by cleaning all the sensor contacts with CRC, that did not help but at 140,000+ was overdue anyway. Then he went leak hunting, because it was not one of the obvious vacuum hoses.

The whistle was a pinhole leak in the gas line at the fuel filter - which was filthy (hey - I just bought the truck, OK?). This caused some starting delays, fluctuations in the fuel mixture which was particularly noticeable at constant speeds.

Replaced the filter, fixed the leak in the fuel line, reset the TPS to the correct settings - apparently this had gotten out with the computer constantly trying to adjust for the fuel mixture. Set the transmission kick down to factory settings and the truck is purring. Bill? $111.73 and he installed my trailer light plug in one of the license plate light holes because the duct tape holding it to the bumper annoyed him.

Thanks to whoever posted the message about sensors because that started him off on the right direction.
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post #12 of 12 Old 02-14-2005, 10:17 PM
zcfd02
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Quote:
Originally Posted by bockwho
if yours also has the power comfort switch on the dash I have been told to keep it in power at all times by a guy that worked on them at a jeep dealer.

I was told this when I was explaing my wandering between gear problem with my MJ.

A tps can also be connected to a meter it should have smooth resistance ohm's

it will also be smooth to the touch you know when you dimmer gets old it breaks and you feel a little skip in it.

When you install a tps you should also get a value. at closed throttle on older 4.0 newer ones do not have a adjustment.

kelsey
I would not advise driving with the truck in power mode unless you are constantly up and downhill. Had my first MJ for many years, the only times I used that switch were offroad (always) and sometimes pulling something heavy, like a powerboat. For normal road driving it only wastes gas.

My old Toyota 4x4 P.U. needed that power switch on all the time because it was so underpowered - not so with 4.0!
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