'98 Jeep Grand Cherkoee Limited, 5.2, full time 4wd.

Picked this up cheap. Had a blown engine so no ability to test drive before purchase. Swapped the engine out and it fired up, idle great, drove it around the neighborhood no problem. When it came time to back it into the driveway, it wouldn't idle in reverse. Sputters, coughs, dies, but no idle in reverse at all. Idle in park, neutral, or drive is fine.

Suggestions on things to check?

Can you keep it running if you apply the brakes with your left foot and use the throttle to keep it running?

Congtats on the V8 GC. They are great vehicles.

Dies in reverse? Strange. Good question about giving it some throttle and see if it stays running. Or if it labors and dies maybe a transmission issue... binding up in reverse?

A fouled up neutral safety switch might prevent crank but I don't think it would kill it once running. Same comment on the shift linkage... should not kill it but would not hurt to check.

It also would not hurt to check any vacuum or intake lines/tubes... is the shift linkage or torque reaction disturbing a damaged line? Same question on wiring... any chafed wires?

Good luck!

Yes, I can keep it running by two footing the pedals, but it is very rough and smells of unburned fuel, and labors a lot to stay running. Otherwise, its starts easy, idles easy, and will work normally in forward gears. Acceleration does seem a bit sluggish, but that may be a perspective from comparing it to my 5.7 Ram.

I'll do a double check of harnesses and vacuum lines. There is a very thick harness running right behind the distributor and vacuum lines galore. I suppose something could be pinched or loose. I'll verify bellhousing and CPS bolt tightness while I'm in there.

How come I'm vaguely recalling an issue like this while I worked at a trans/gen. auto repair shop, and the trans cooler-hoses-obstruction of some sort was the case.? In other words, be sure the cooler flows well.

The transmission line pressure increases by a factor of 3 in Reverse, this adds to the engine's load so an engine with tuneup problems might not run correctly with the added load of the transmission pump and could stall.

Wow---that's pretty obscure stuff John! Never heard of that. So it's possible for idle in reverse to be a bit lower than in drive?

Interesting. Learn something every day.

Yeah, pressure is high in reverse. This can cause fluid to bypass some seals. Sounds like the torque converter clutch is being applied, at least partially. This could be a converter problem or it could be in the trans. I seriously doubt it would be wiring related.

The engine to trans mating during assembly was a bit of bear, but it eventually went thunk, and all came together. Wouldn't think there is the possibility of a mis-alignment and binding or forward gears would have an issue. I'll check all the trans bolts to make sure they are tight. Would disconnecting the cooler lines and blowing them out be a benefit? It would sure suck to have a convertor or trans issue, but since the previous owner grenaded the motor travelling down the highway, is it possible that put a hurt on the trans?

Nearly anything is possible. 42 years in this business and I still see stuff I've never seen before. I don't think it's misalignment and blowing the cooler lines out probably won't help. It wouldn't hurt to check the cooler flow though. Even if that caused a seal to bypass fluid the damage is probably already done and it will need to be repaired.

Check crank sensor for intermittent signal. I had a Ram pickup so this same thing a few years ago and found the CKP to be defective.

X2 with Guitar Jones. One thing to look at is the trans converter engaging. Try feathering the gas in a parking lot and see if the Jeep takes off like a stick shift truck,it may take a few times. You must understand hyd pressure hold OFF the converter clutch any low line pressure from wear plus reverse needing more pressure adds to a drop in pressure enough to cause the clutch to engage and stall the engine. BTW it's not a faulty converter it would be a wear problem most of the time in the frt pump area. IMO

Thanks for all the input guys. With 225k on the clock, I'd lean towards wear necessitating a rebuild.