1988 automatic 4.0 transmission problem
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Year: 1988
Model: Cherokee (XJ)
Engine: 4.0
1988 automatic 4.0 transmission problem
I have a drivetrain stock 1988 cherokee 4.0 with the aw4 automatic and selec-trac 4x4. The transmission was rebuilt about 10,000 miles ago (currently at 232,500 miles) and has been maintained. The problem is, it shifts out of gears at 4,000 rpm, not 5,000, doesn’t downshift into first gear over 20mph, the torque converter doesn’t lock up properly, it will rev up and down continuously in third and fourth gear, sometimes won’t downshift from fourth, if it’s in the 1-2 gear selection if second gear isn’t being used at full throttle at any speed over 35 the car will downshift to first (once happened at 60 mph). I’ve checked the throttle valve “kickdown” cable, fluids, got a new throttle position sensor, and even put in a new ECM/ECU. Nothing has changed. If anyone knows how i could fix it or if i need a new trans, email me at thomashtont@gmail.com. This is also my daily driver so if anyone has any idea, please contact me. Thank you.
#2
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Location: Prescott, Az
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
ECU has nothing to do with trans shifting. TCU does.
How did you adjust the new TPS?
Here's something to do:CRUISER'S MOSTLY RENIX TIPS
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.
All the components listed below ground at the dipstick tube stud:
Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for its intended use and subject to corrosion and poor connections at each end.
I prefer to add a #4 gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18″ long with a 3/8″ lug on each end works great and you can get one at any parts store already made up. NAPA has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10″ long with 3/8″ terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. NAPA part number 781115.
For those of us with Comanches, it’s very important to remove the driver’s side tail lamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply also.https://i1.wp.com/cruiser54.com/wp-content/uploads/2015/10/Fuel-Pump-Ground-Comanche.jpg
If you want to upgrade your ground and battery cables with custom made parts, contact Neal at www.meanlemons.com
How did you adjust the new TPS?
Here's something to do:CRUISER'S MOSTLY RENIX TIPS
RENIX GROUND REFRESHING
OCTOBER 30, 2015 SALAD 38 COMMENTS EDITThe Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.
All the components listed below ground at the dipstick tube stud:
Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
- Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. If the whole stud turns, you can use a 7/32″ six point socket or wrench to hold it so the nut can be removed. Worst case, cut the wires and remove the stud and nut. Install new terminal eyelets on the wires when going back together. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Surfaces must be clean, shiny and free of any oil, grease, or paint.
- Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Apply a liberal coating of , which is available at Lowe’s and other stores. Reinstall all the wires to the stud and tighten thhttps://i0.wp.com/cruiser54.com/wp-content/uploads/2015/10/dipstick-stud.jpge nut down securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for its intended use and subject to corrosion and poor connections at each end.
- Remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Apply . Reattach securely.
- Remove the other end of the cable from the rear of the head using a 3’4″ socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely with a liberal coating of .
I prefer to add a #4 gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18″ long with a 3/8″ lug on each end works great and you can get one at any parts store already made up. NAPA has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10″ long with 3/8″ terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. NAPA part number 781115.
For those of us with Comanches, it’s very important to remove the driver’s side tail lamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply also.https://i1.wp.com/cruiser54.com/wp-content/uploads/2015/10/Fuel-Pump-Ground-Comanche.jpg
If you want to upgrade your ground and battery cables with custom made parts, contact Neal at www.meanlemons.com
#3
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Join Date: Aug 2011
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Here's another one.CRUISER'S MOSTLY RENIX TIPS
Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself
. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.
Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.
TRANSMISSION CONNECTOR REFRESHING
OCTOBER 30, 2015 SALAD 13 COMMENTS EDITOver near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself
. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.
Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.
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