Gearhead41987

Hi All,
I'm a pretty good mechanic, but I'm new to Jeeps and the quirks that they have...
I have a '96 Cherokee sport, 3" lift and 31-10.50 tires. My motor blew up right after I bought it, so I had it replaced with the motor from a 97 Wrangler. It has been running GREAT. No smoke, blowby, noises, or oil burn.
However, I decided to run some fuel system treatment through it. I put it in a full tank, and last night (by then I was on 1\4 tank) When I was driving on the interstate (about 70mph) It would buck like the motor died, then came back and ran fine... It did this a few times randomly, so I slowed down a little, but it still did it randomly. I went to the pub, had a pint, and then went back to my jeep and when I cranked it up, it died within three seconds, cranked right back up then did the same thing again. The third time it stayed running fine. But when I put it in reverse It dies instantly. Like I turned the ignition switch off. Cranks right back up. If I put it in drive it runs fine. But thus far I have yet to get it to stay running in reverse. even if I let it roll backwards on a hill then put it in reverse so the motor doesn't have to slow down. If I feather the throttle, I can make it keep running, but it bucks and you can't get anywhere. It seriously feels just like It would if I were to turn the switch on and off. I'm going to replace the fuel filter today, and I'll clean the IAC valve tonight, but I'm almost thinking electrical.... But everything still works with the ignition still on and the gear selector in reverse. So I don't really know... Any suggestions? Cause I can't come up with a good reason for it to start this all of a sudden...

wicked_xj

is it auto or manual?

okcjeeper

Man I wish I could help but have no clue where to even begin..Only thing I could possibly think of is a torque converter...just seems odd it would happen after adding some fuel additive...

Gearhead41987

It's an automatic...

I wondered about the torque converter but if that were the case, I feel like it would die in drive as well as reverse. And it doesn't buck, or lurch, or slam into gear, the motor just stops running...

BlueXJ

Sounds electrical to me too. Check all the grounds and see if you can get someone to help you so that you can see if there is juice to the ignition system in reverse. I think it is going to be wireing related. The fuel system cleaner was just a coincidence IMHO.

okcjeeper

Anothing thing is the idle speed motor on the throttle body, fuel filter could be an issue as well..To me if it was the fuel pump it wouldn't work period or would stall even in drive...Only reason I said torque converter is it did it in drive then stuck with just reverse..

Gearhead41987

Are the trannys computer controlled in the 96 XJs?

Or do you think somthing's shifting around and getting shorted?

BlueXJ

Yes the AW4 is electrically controlled by the TCU. It is a seperate computer from the ECU. On earlier models they were incorporated into one but after 91 they are seperate IIRC.

Gearhead41987

Where is the TCU located?

wicked_xj

i hate newer cars so much comp $HITT

Gearhead41987

Wicked just explained why we have 80% of automotive problems right there...

drove it on my lunch break, managed to get it rolling backwards in an emty parking lot and after it went into reverse, I was able to keep it running, (bucking and shaking) for a few minutes, then it went dead.

So, I pulled into the local drive thru, and they were taking forever so when I pressed the accelerator down to pull out of the drive thru, it konked out. Felt exactly like fuel starvation I barely made it back to work, every time I'd press the accelerator it would just shake and buck untill it hit 3000 rpm, then it'd smooth out...
Now it's fine, but it's back to dying in reverse.
(I put a new fuel filter in it over lunch too... No difference at all and it had PLENTY of fuel pressure on the line when I took it off...

okcjeeper

Well signs of a bad torque converter is when excelerating the vehicle sputters/bucks until you hit a certain rpm an then it corrects itself...Check the tranny fluid to see what color it is and what level it is at...In reverse I don't think you could hit those 3500+ rpm ranges to correct the sputtering...I had a converter go bad on me on a turbo 350 tranny and the engine would stall out unless I just hammered the heck out if and got the rpm's up there..Just something to think about...Signs could be a brownish tint to the fluid or a foamy appearance...Worth checking out none the less...

Gearhead41987

I checked the tranny fluid and it seems like it's in pretty good shape...

Now, the thing that makes me think it's not the converter, is that when It started messing up on me when I was driving forward, it died several times when it was in neutral. Then started doing it only in reverse again... The A\C compressor is off, and is spinning freely, so I know it's not that...
I'm utterly lost. I can't find any bad wiring, I 've pulled all of the injector connections off and they are all working properly. And EVERYTHING else works fine.
I think I've been by this thing...

okcjeeper

Just a little off direction but worth a check...Have you checked to see if you have water in the oil..Sounds odd but at this point just brainstorming any possible issue that could cause such a thing...I'll ask a budy of mine who's a mechanic is he has any suggestions...

muddeprived

Other signs of bad torque converters are stalling and pressing the gas and no response. I had two bad tc's in my ex TJ. It would go and then just rev up and go no where. Reverse was the same and sometimes it would shut off due to the rpms skyrocketing. Sometimes when i press the gas it would sputter a little and just barely move.

Have you tried putting it in 4low and going in reverse? My bad torque converter wuoldn't let the jeep move unless it was in 4low, but it just barely was able to move even then.