power cutting at constant speed????

[jeepmedicNB]

Well ive owned my cherokee for a month now and it has just started acting up a little bit, I just got done a 400km trip and the entire time the xj would hesitate, or lose power momentairly when maintaining a constant speed, if I increased throttle it would clear up imediatley and accelerate like normal?
All I have done so far is make sure the plug wires and coil wires are tight and add some injector cleaner, same problem still. any help would be greatly appreciated.

thanx
curtis 97 TJ 4.0

[87manche]

did it happen at the same throttle setting consistently? Check the TPS, it may have a dead spot at "cruising" throttle position.

[Xj'sR'Creamy]

I would replace cap, rotor, wires, plugs, clean out the TB buy a new battery, new 02 sensors, and anything else that is simple like that, then take it from there.

[jeepdude10000]

did it happen at the same throttle setting consistently? Check the TPS, it may have a dead spot at "cruising" throttle position.

I would go this way

[Saudade]

Take it somewhere and have them pull the codes to see what's going on. Otherwise, I'm with 87manche. Check the TPS.

My '88 XJ did some funny things at 45 MPH. Below 40 (or so) it was fine. Above 50 or so, it was also fine. Tested the TPS and found it had a bad spot. Swapped it out and that fixed it.

[scca28]

I posted this a couple of weeks ago on another thread:

I was getting some violent bucking that would occur once in a while, then not happen for a few days. I started to notice that it would happen around 30-35 MPH. Above or below it was fine. I tried checking my throttle position sensor with a digital meter, but didn't see any drop off. Later I found a post, by 5-90 I think, where it says an analog meter is better for that particular test. Anyway, before I read that,I had already swapped in another TPS I had from the U-PULL-It. So far it has been running smooth throughout the entire throttle range.
Curiosity set in and I had to cut open the old TPS. Inside is a rolled piece of what looks like photographic negative, with 4 traces of resistance material printed around it. In the center is a rotating shaft with 4 pickup wipers made up of 3 tiny fingers on each. I can see where some of the resistance material is worn away at one spot,and I'm pretty sure the fingers have lost some of their tension. The whole unit is sealed from outside elements, but now I can see how normal wear will take it's toll on these sensors.

[anony91xj]

What year is the Cherokee we're talking about here? Is it a Renix with an EGR valve?

[jeepmedicNB]

ya, the cherokee is a 97. It has good days and bad days, still missing or skipping at certain constant speeds, but most often at 60mph on the highway, it also started stalling quite often when I am down shifting in a parking lot and put the clutch in to park the jeep it often stalls before I shut it off, also in traffic when coming toa stop..... but it always starts right up..... don't fail me now starter! lol THe jeep hasn't left me stranded yet and I have been procrastinating on taking it in to get diagnosed. Just got done paying for mud tires..... oh well, you know how priorities are.

THanks

[jeepdude10000]

Ok now u need to change the TPS!

[jeepmedicNB]

okay then, I know this is a stupid question but where is the TPS located anyway? probablt somewhere near the throttle body but I ma not the most mechanically inclined person, I ma much better at breaking things and getting stuck in inconvinent places....

Keep on Jeepin!

[jeepmedicNB]

I would replace cap, rotor, wires, plugs, clean out the TB buy a new battery, new 02 sensors, and anything else that is simple like that, then take it from there.


And you credit card number is??? lol

[SanDiegoXJ]

Well the tps is located on the throttle body nearest the firewall. You should see two sensors there, an IAC (Idle Air Control) valve and your TPS (Throttle Position Sensor). The TPS will be closest to the driver side quarter panel and the IAC will be closer to the valve cover.

I have a similar problem with my Jeep. Only at cruising speeds will it buck/hesitate on the freeway. If I accelerate the problem goes away. I purchased a brand new IAC and TPS from autozone and installed them. Immediately the Jeep began to idle at 3k rpm. After fiddling a bit, the engine recalibrated and settled to normal idle speed. However, after that I had a rather rough idle. Just for shits and giggles, I replaced the IAC with the old Mopar piece after cleaning it...the rough idle went away. The hesitation at cruising speed seems to remain constant tho.

I'm pretty sure the autozone IAC was crap from the get go, but I'm not sure if the TPS is the same...I can't really tell if the problem changed at all between the two. I also noticed that when the Jeep starts to buck and hesitate the revs jump up and down a bit like its attempting to downshift. I'm very curious to see what your resolution is as I have yet to find one.
:rattle:

Good luck!

[GreenGhost]

I'm having a very similar problem with my '97 XJ. I would get a slipping, or stuttering usually while cruising, though not at just one speed. I pulled codes for the IAC (P0505) and TPS (P0122). I replaced both of those, but kept getting the codes. Bought a ODB II reader and cleared the codes, but they come right back. After replacing the sensors the idle became very rough, but not consistently, and usually, once it warmed (didn't take long in current heat wave), it would run more or less fine. Seems like the idle issue has been getting progressively worse, and now I can barely keep it lit. It stumbles, with considerable shaking down to about 250 rpm, comes back up to about 700 several times, then it seems to idle just fine for a bit. But if I drive it, it'll stumble and die. Now in the garage it'll just keep stumbling and revving, then die.
When I replaced the IAC I couldn't resist cycling the piston a few times with my simeon fingers to compare the action to the old one. I read another post (after doing this) that warned against moving the sensors by hand. Did I pork it up by doing this?
I'm also getting a P0700 code for "Transmission Control System Malfunction", and P0756 "Shift Solenoid B CKT Performance or Stuck Off". Are these related to, caused by, or possibly causing my other woes? Or is this a whole 'nuther nest of snakes?

[lazarus]

I know that when my tps went in july of last year it also threw those tranny codes, as the tps is used for shift points and a lot of other functions.I replaced mine with an autozone unit in july last year, and now it seems to be bad again. Found that oreily has a borg warner unit for less and a lifetime warranty to boot. Ill be doing that tomorrow after work!

by the way, its a 98 sport with 169k on it.

[GreenGhost]

Thanks Lazarus,
Turns out a great deal of my wiring loom had fuzed together. Including the circuits responsible for those sensors. Had to replace a good portion of the wiring for the whole Jeep. Looking at the loom it's a wonder the thing ran at all. Wires were melted together in at least 7-8 different spots. Now I need to figure out why. The trouble seemed to start when I went to start the Jeep and didn't hold the key at "Start" quite long enough for it to catch. Anybody think that dose of high amp, electro-love without consumation gave my circuitry priapism?