codfish

Hello everyone!


My 92 4.0 XJ auto tranny has and issue that I cannot figure out.


Here is what I have done: Cap, rotor, wires, plugs, vacuum leak check and a tranny service.


Here is what it does: When I'm on it hard....climbing hill in second gear or on the road passing another car....it cuts out, but comes right back. All engine power drops out for half a second and then comes right back. Not certain how to explain it.


It runs fine past that, drives and idles fine and runs good. Only happens when it is under load.


Any help would be appreciated.

RTorrez1

Have you checked it for any codes? That would be the first thing to do.

codfish

Good question. No codes. No CEL.

codfish

bump....any other ideas?

codfish

I have just about emptied every pocket and I still don't have a resolution to my issue and it is getting worse.


I have now thrown a coil and a TPS at it. I have gone through the vacuum lines and only found one bad end at the fuel pressure regulator.


I took it for a test drive tonight...after the new parts...and watched carefully. If I accelerate from a stop smoothly it will run perfectly. No issues all the way to 65. If I give it some gas and it downshifts it will run fine until it gets to approximately 3500 RPM. Once it hits 3500 the engine stalls long enough for the RPMs to drop to 2500 and then it fire again and run until it hits 3500 and it drops out again.....it did this three times in a row and I finally let off the gas and all was good. Normal driving it does not have an issue.


Could it be a fuel pump? What symptoms are generally experienced in a XJ?


Totally stumped. Help please!


Thanks,
Codfish

Roler

Well, doing a fuel pressure test would give you an idea...

DJeXeCute

Sounds like fuel starvation check fuel pressure.

codfish

32 lbs. that would explain it. Bummer. I don't want to replace it again.

Roler

Your year would be 39PSI +/- 5 IIRC.. 32 is not a complete failure but could explain the higher RPM range cut out.

What you mean with 'again', when did you replace it?

codfish

I replaced it about 4 years ago. It's not hard but I had issues getting the tank to seal...fought it for a year or so.

I thought I read that it was supposed to be 49 lbs.

cruiser54

Any mention here of a fuel filter being replaced?

If you used an Airtex pump 4 years ago, it would be a long lived one.......

Could be as simple as the hose INSIDE the tank from the pump is split/soft/loose or otherwise FUBARed.

codfish

Yes...filter has been replaced...yesterday before the pressure test. I don't know who provides Napa pumps. But they were the only ones that had the pump in the town that I bought it in. Just found my receipt 9-16-2010...almost 4 years.


I heard something from an old Jeep guy that I know. He was saying that the Bosch fuel pump is a upgraded pump for the walbro pump. Any truth to this?


Thanks for all your help!
Codfish.

cruiser54

Bosch is good.

codfish

Crud. Still stumped. New pump....same problem. New pressure regulator...same problem. Checked codes. 13 map sensor. Still no CEL. New map sensor...same problem.

I give. It's going to the shop in the morning.


Thanks for your help.

mitch500

Check all your grounds/refresh them. Sounds like if you loose all power it's a electrical power loss. Fuel cut it would stutter a bit then come back.