Strange "Power" problem

Alllll-righty then. It's a '92 xj. With the wondrous 4.0ho. (Yes my xj is a ho.) I am the second or third owner so prior repairs, in other hands, I know nuthin...

Here is the situation.
Power on take off is good to moderate. Enough so that If I had never felt it's ability, I would not be the wiser. But when pulling into tight traffic, foot to the floor, after about 5-7 harrowing seconds, power boost jumps like it has a turbo. (It doesn't.)
I believe a related issue, when I just stop and shut down for a couple of minutes; I restart, idle high and lowers as expected, then xj spudders, pops through the carb. Essentially acts as though the gas bad. sometimes dies when put in gear when it does this. Forced foot down gets it going after a minute or so. Will get complacent in regular driving modes and takes a foot to the floor treatment; with down-shift and will jump in RPM; to fix in motion.

Checked the cam sensor.
cleaned the cap and rotor.
burst of power says to me that the fuel pump is good.
power also says to me the filter is good.
oil changed within the week with full synth.
oil filter too, of course.
removed and inspected ecu plug. looks good...???
Replaced 02 sensor but havn't gotten to the dealer to reset light yet. Still shows a bad O2 sensor. (Would that effect it?)

Long and wordy, I know.

P.S. I just changes a mangled u-joint on the front passenger side. Still didn't fix the 45-55 vibe. (Yes I tried diff gears, same speed same prob...)

Oh...Darn...
It's a 92 Loredo
4x4
auto tranny
4.0 ho as I said....
Ummm...That's about it I think...
Thanks

Mine also at startup Sometimes pops from the carb and has like no power and would die if gas isnt feathered down to the floor once rpms get up goes back to running normal. Does yours Happen at random as well? it will also happen sometimes if idle too long..
Sometimes this trips the M.i.l. and it reads as multiple misfires

(edit) So im no help but ill be waching to see the replies you get

These trucklets don't have carbs fellas. lol. Fuel injection is a marvelous thing.



Did you check for codes? I've got a 1992 as well, and our OBDI system is great at letting me know what's going on. Doesn't need to have an engine check light to blow and store a code.

Grab yourself a pen and paper, and sit in the drivers seat parked in your driveway, parking lot, etc. the car does not get started during this process. Just move the key from the on, to off postion

Start with the key off.

Flick the key on, off, on, off, on...and then leave it on.

The check engine light will then tap out a morse code rhythm...1 flash - pause - 7 flashes - pause, etc.

It will always end with 55, so you might get 12, 24, 55 as your codes, for example.

Try that and post up what you find. If you do it right, I'll post up the translation

SanDiegoOverland said:

These trucklets don't have carbs fellas. lol. Fuel injection is a marvelous thing.

Click to expand...

:doh: Duh! LOL ok so popping and sputtering from somewhere up there lol

Clogged Cat Conv maybe... sounds like you have more than one problem.

CherBear said:

Clogged Cat Conv maybe... sounds like you have more than one problem.

Click to expand...

Thats kinda what I was thinking, too.


It'll be interesting to see if there are any codes from the computer.

@Sandiegoverland...
No carb but didn't want to confuse with going through the injectors. (Yes I have had some body think I meant that.)
Code is 12. I knew that trick. It is great not to need a OBDii, (Even know I have one already.) Just replaced the o2 sensor.
Thank you though...

@Cherbear..
I hope not. that would suck. Mucho dollero!

You know guys and gurlies,
The way the power is kickin in, it doesn't sound muffled and the exhaust seams free flowing. Granted my exhaust over the Axel is rusted through and the tail end is...well..gone, but the rest of the exhaust looks in pretty good shape. Newer even. Probably had a lazy shop cut the end piece so they wouldn't need to do the bend.

The power litterally waits and then, GOES like a bat outa hell. Cuts the back tires loose on wet surface even know your already movin pretty good.

jeep_Hulk said:

@Sandiegoverland...
No carb but didn't want to confuse with going through the injectors. (Yes I have had some body think I meant that.)
Code is 12. I knew that trick. It is great not to need a OBDii, (Even know I have one already.) Just replaced the o2 sensor.
Thank you though...

@Cherbear..
I hope not. that would suck. Mucho dollero!

Click to expand...

Ah, I see, on the carb thing. gotcha

Also, good that you know the OBDI voodoo... Didn't want to sound condescending at all, just felt like throwing it all out there in case you didn't know or if someone saw this thread and was seeing it for the first time.

It's all good, man.
I'm gonna figure this beasty out!!!!

My Grand wagons were so much easier to figure out. XJ's biggest problem are the sensors. Cam, vac advance, throttle position, blah, blah, blah. (Not as bad as my Mkiii supra though. 5 comp boxes on that sucker and a yellow break box did me in a 135mph. Flew that sucker 40ft over 12 feet in the air.)

Hey! What do you guys think about a sticky fuel pressure regulator...? Does that happen? I was just on the road a minute ago, floored it, got the little power and the it took 5 seconds on the stop watch and kicked me in the hiney with the "Boost." I know this thing wants to please me. It has the horses ready to run. I just can't figure out how to un-tie them...