1990 4.0 automatic no power in drive, runs fine in reverse

[r1volta]

1990 4.0 automatic has no power in drive but runs fine in reverse

[gogmorgo]

Not much to go on. Does it not move, or does it just struggle to do so?

When was the last time you checked the trans fluid?

Have you tried unplugging the trans computer to shift manually?

[cruiser54]

Not much to go on. Does it not move, or does it just struggle to do so?

When was the last time you checked the trans fluid?

Have you tried unplugging the trans computer to shift manually?

Agreed.

 

Could be a blown/corroded fuse to the TCU. 

[Eagle]

Does it run if you shift manually to "Lo"?

[cruiser54]

Well, it appears that we care more about fixing his Jeep than he does.............

[r1volta]

Sorry for no responses to the help. Jeep is in Oregon, I am in Mass. Work schedules and time difference will delay any work until weekends

[r1volta]

Trans fluid is clean and full

All grounds removed and cleaned

Have not tried driving in low because the engine is now running very rough

I am waiting on results of fuel pressure test

EGR is clean and working

Plugs are new

[cruiser54]

Are your engine to trans bolts loose or missing?

 

CPS harness routed properly? 

[Eagle]

To check the tranny, the FSM instructs us to remove the TCU fuse and shift manually. When driven that way you lose one of the two low gears when in the "Lo" position -- second gear, IIRC -- but otherwise you should be able to drive it by shifting manually. This is to diagnose whether the problem is a transmission problem or a TCU problem.

 

You also want to be sure the shift linkage is properly adjusted. That's why I asked if it runs in the "Lo" position.