Deman686

Was wondering if anyone would no why my 90 jeep Cherokee die when I put it in gear? It seems like the fuel pump shuts off when I shift it into revers or drive. any help would be great. Oh and what would be a good locker for a 8.8 ford rear end?

dougfrompa

Some more info would be nice. Auto or man.? engine type? Is it all stock? What other modifications have you made?

BotakBeng

First thing i would do is check your tranny fluid condition and level, might want to consider replacing the tranny filter.

Locker for 8.8? I would get the Jeep to be road worthy before even think about locker or 8.8 swap (assuming you having got one yet).

CPLSeraphim

I'm going to assume automatic here since he says reverse or drive.

Does it clunk when you shift? try revving right when you shift, or maybe going down to first. Also, it is dying as soon as you shift or when you try to move? Please be as specific as possible so we know where to aim.

tjwalker

1. Clean both your throttle body and your idle air control. See below.

2. Test AND adjust your throttle position sensor. See below.

Good luck and keep us posted!
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RENIX (87-90) TPS ADJUSTMENT

Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.

IMPORTANT NOTE: Using one lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the other lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.

MANUAL TRANSMISSION:

RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.

Wire "A" is positive.
Wire "B" is ground.

Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.

Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.

AUTOMATIC TRANSMISSION:

RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.

However, the automatic TPS also has a four-wire connector clearly embossed with the letters
A,B,C, and D.. For the automatic transmission equipped vehicles the four-wire connector
provides data to the TCU.

Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.

Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.

So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.

For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

DFlintstone

Agreed with the above^^. Is the Jeep new to you? There is a solenoid that locks the torque converter. With it locked, it's like being in gear with the clutch out. There is a modification where a switch can be added to lock it. A long-shot, but do you have any "misery" switches?

Also the wires to your TCU right there below the glove compartment are in a place where they could have been messed with/up. You might take a quick look and see if they look OK.

Also if the problem is "in that department", can he try unplugging the tranny wires behind the dipstick tube?

Also take a look at the engine-to bell-housing bolts.

Deman686

Thank you all for the info. It ended up being a hacked wiring.. The guy I bought it from was a hack. Ended up running the fuel pump on a switch and it works great. Drive great and can't wait to put more into my jeep.

tjwalker

Thanks for checking back. Glad you found it. Now get your checkbook out and start modifying your Jeep. The tough economy needs your cash infusion!

CPLSeraphim

^LOL. that is hilarious. I'm an econ major in college, and my professor would tell me the exact thing. SPEND MORE MONEY!!! lol.

@OP, this is a great place to get ideas for your jeep, but it also has a tendency of putting a lot on your to do list at one time. Trust me, i know but yeah, and the ideas here are great.

I am glad you found the problem. Don't you love hackers? lol. They don't know what they are doing and just cut away. lol