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Shifting is Acting Up...ECU? HELP?!?!

Old Jul 27, 2012 | 12:07 AM
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Default Shifting is Acting Up...ECU? HELP?!?!

Here's the deal. I was driving home (1996 Jeep Cherokee Sport 4.0) one day and all of a sudden as I was taking off my RPM's went up and I was barely moving. Checked all my gauges. Nothing outta wack. Had it floored. Maybe went 15 mph TOPS. Blew every stop sign and red light so I wouldn't have to stop. Almost took 2 mins just to get to 10-15 mph.

Pulled over. Popped the hood. Nothing seemed wrong. Drove it home. What normally is a 10 min drive took me 45-hr. Drove it to my pops, we got in. Cranked it. Drove beautifully. Like nothing happened.

Now I have to turn my jeep off and on quite often. Ill drive. Stop. Same problem. Wont go. Or, barely. Turn off and on. Drives fine. Took it to my mechanic and 2 tranny shops. No problems, codes. Nothing.

Is my computer going outs on me slowly? Suggestions? If it is, I wanna buy a new one. Not a junk yard. If its something else someone else has dealt with, anything would help. Seems like it is a computer seeing as how all I have to do is turn my jeep off and on and it runs like new.
Thx!
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Old Jul 27, 2012 | 12:15 AM
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Pull the connector for your TCU, shift it by hand and see if the problem's still there. Assuming you checked the Trans for proper fluid level and condition already...?
TCU is the Transmission Control Unit- the trans. has it's own computer. It's behind the lower passenger's side knee panel.

Last edited by Radi; Jul 27, 2012 at 12:22 AM.
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Old Jul 28, 2012 | 05:03 PM
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Yea, all fluids and filter are good. Can I disconnect the tcu and shift by hand in an automatic? Cause the problem doesn't always happen. But when it does, i have to turn the jeep on and off several times in a trip. Also, there no warning as to when it happens. Ill go to say pull out and it will barely move lol. Sucks!
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Old Aug 3, 2012 | 01:23 PM
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I been blindly trying to fix my problems also as it takes time to accelerate while increasing to uncommon RPM's.... Everyone is tell me its a clogged cat converter, TPS, Crank Sensor or ECU....then every auto shop is telling me they can't really diagnosis a 93' grand cherokee cause its a OBD. So I don't know what to fix since it could be multiple things
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Old Aug 3, 2012 | 04:05 PM
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Originally Posted by ChrisColey
Can I disconnect the tcu and shift by hand in an automatic?
Sure. it'll shift from 1st to 3rd (no second unless you really rev it up) and no torque converter lockup...but it's fine to drive that way for test purposes.
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Old Aug 3, 2012 | 04:47 PM
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Originally Posted by Radi
Sure. it'll shift from 1st to 3rd (no second unless you really rev it up) and no torque converter lockup...but it's fine to drive that way for test purposes.
And it's what you should do for troubleshooting purposes. If it shifts fine with the TCU disconnected, that means that the transmission is fine mechanically and that you have an "electrical" problem and that leaves you with primary suspects of the throttle position sensor and the TCU itself.
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Old Aug 3, 2012 | 04:56 PM
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Although may not be your issue it's alway wort trying and FREE which is best. Have you ever adjusted you kickdown cable. Yours should have the same setup either the D button on the cable or the white clip. The cable is on the TB

Last edited by sycoglitch; Aug 3, 2012 at 04:58 PM.
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Old Aug 3, 2012 | 08:03 PM
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The problem is it is not downshifting into 1-2 when you stop. Does this happen after its warmed up or always? If you continue to drive starting you will burn up the trans. It could be the TCU or shift solenoids or the wiring. If it does it after warming up Id say 1-2 solenoid. The TCU is cheap at a pick and pull for a quick try.
http://www.jeepforum.com/forum/f11/a...no-56k-717206/
Here is a link to testing the the solenoids. Test them at the TCU so you are checking the wiring also.The solenoids are about 225 from an outfit in Florida.
http://www.bulkpart.com/Merchant2/me...e=A340solenoid
The solenoids fit pre and post 96 Aw4s.
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