New Trans, No start

I have an 88 Cherokee buggy thing. It has the original 88 motor in it, but I just swapped in an auto trans from a 98. It had an auto before, but it was worn out.

I have the original CPS hooked up, but neither plug from the transmission is plugged in. I have the starter hooked to a push button. The fuel pump also hooked up to its own switch.

I will be using a stand alone shifter from RADesigns. Is there anything on the trans that I need to hook up? Does the TPS run through the trans? My motor will crank, but not start. Any other reason it wont start? Help!

Did you change the flexplate when you changed the transmission?

No, stock flex plate.

I installed a new CPS and now I am getting spark, but the engine is running like absolute crap. It wont idle, it will only stay running if I mash the gas pedal. It is back firing and missing like crazy. Any thoughts? It ran just fine before this transmission swap....

-pinch a fuel line during the swap?
-engine sag on it's mounts and pull the ground straps off?
-engine sag on it's mounts and pull MAP sensor vacuum hose off?

You need to figure out the trans wiring, and yes, the auto TPS is through the TCU.

joe_peters said:

You need to figure out the trans wiring, and yes, the auto TPS is through the TCU.

Click to expand...

A beam of hope in a miserable situation. Does anyone have a wiring diagram for the trans? The TCU is still hooked up under the dash, but nothing plugs into the trans...

The motor is running awful. Sounds like the timing is way off. Its backfiring out the exhaust. Sounds like computer is trying to take control and rev the engine sometimes and it kinda evens out (even tho it is still running bad, just not nearly as terrible.) Other than the tcu, any chance it could be the computer?

joe_peters said:

You need to figure out the trans wiring, and yes, the auto TPS is through the TCU.

Click to expand...

Huh? The 88 TPS has dual outputs, one of which goes to the engine and the other to the Trans computer. Not having the tranny connections plugged in won't make any difference. Now using a 98 tranny with the 88 Trans computer is a whole nuther ball of complicated wax.

lawsoncl said:

Huh? The 88 TPS has dual outputs, one of which goes to the engine and the other to the Trans computer. Not having the tranny connections plugged in won't make any difference. Now using a 98 tranny with the 88 Trans computer is a whole nuther ball of complicated wax.

Click to expand...

Huh? The 88 automatic TPS is adjusted based on the reference voltage provided BY the TCU. No reference voltage, no adjustment, ECU is probably very confused. :wave:

Well it ran just fine when I didnt have TCU in it all last year. I only recently put the TCU back in with the old trans. As of now, the TCU is plugged in, but the two plugs that go to the transmission wiring are not plugged in. The plugs are between the transmission dipstick and oil dipstick...

Those plugs also handle the rear O2 sensor (if it exists on RENIX, I forget) so you may need them to be plugged in.

kastein said:

Those plugs also handle the rear O2 sensor (if it exists on RENIX, I forget) so you may need them to be plugged in.

Click to expand...

only 1 o2 sensor on a renix and its on the exhaust manifold.


88xjscott,

what year cps did you install? needs to be an 87-90 renix cps.

is the cps setted proporly? pinched cps wiring?

Its an 87-90 CPS, i will check to make sure it is sitting properly tonight, no pinch, i double checked cause thats the reason I replaced the one that was in there.

Check to see if you are getting reference voltage to the 4-wire connector on the TPS.

So if anyone can help me out, they might be my life saver:

Here's waht I have for the wiring situation with the trans... I have isolated off the NSS wiring (which I am assuming I no longer need because of my bypass switch)


The other plug out of the two has the following wires in it:

Plug on the jeep side (from an 88 XJ):

White/Black
Purple/White
Blue/White
Tan/Black
Black/Red
Yellow/Black
Black

Plug from the trans harness (From a 98 XJ trans):
White/Black
Light Purple/White
Light Blue/White
White/Brown
Black/Red
Yellow/Black
Black


Does anyone have a wiring diagram for the transmission or TPS or anything to help me figure out which wire does what. They are SOOOO close that I'm tempted to just jump them all straight across, color to color, but I dont want to blow the computer or tcu because I rushed it. Then I have more problems...


HELP!

From the 99 FSM
=================
1: 20RD/BK - INPUT SPEED SENSOR SIGNAL
2: 20OR/WT - TRANSMISSION SOLENOID A ***
3: 20WT - TRANSMISSION SOLENOID B ***
4: 20DB/WT - TRANSMISSION SOLENOID C (LOCKUP)
5: 20VT/LG - INPUT SPEED SENSOR GROUND
6: 20DB/BK - OUTPUT SPEED SENSOR GROUND
7: 20LG/WT - OUTPUT SPEED SENSOR SIGNAL
8: empty


From the 98 FSM
=================
Pin 1 - Red/Black - Inout Shaft Speed Sensor Signal
Pin 2 - Org/White - Trans Solenoid A ***
Pin 3 - White - Trans Solenoid B ***
Pin 4 - Dark Blue/White - Trans Solenoid C (lockup)
Pin 5 - Violet/LtGreen - Input Shaft Sensor Ground
Pin 6 - DarkBlue/Black Output Shaft Sensor Ground
Pin 7 - LtGreen/White - Trans Output Shaft Speed


From the 97 FSM
=================
CAV CIRCUIT FUNCTION
1 18BK GROUND
2 empty
3 20WT TRANS SOLENOID A
4 20LG/WT OUTPUT SHAFT SPEED SIGNAL
5 20DB/WT TRANS SOLENOID C (LOCK-UP)
6 20OR/WT TRANS SOLENOID B

***The 98 and 99 FSMs seems to have an error though as
the Solenoid A and B colors are swapped if you look
at the TCU connector. The 97 is consistent and show
Solenoid A as Org/White and Solenoid B as White


With all that regurgitated. I remember when I swapped a 99 into an 89, that the colors on the trans side of the harness didn't match the vehicle side of the harness. When I traced everything out I found that everything was in the matching places on the connectors (although they didn't mate up) and that all of the colors I needed to connect were _almost_ the same. For example instead of violet with a white stripe it was white with a violet stripe.