Hello again!

So, I have been trying for quite some time now to figure out what is causing this occasional jerking that I am getting from my 99 xj.
Alright, to be honest, is it jerking?, surging, lurking? I'm not exactly sure what to call it. All I know is it's tied to the gas pedal, and it always goes away when I let off the gas. Maybe one of y'all can give me better terminology.
Forgive me lol but it's also kinda like a bump. When it happens its like bump and bump bump bump in which i let of the gas and it goes away. Seems to happen mostly when I'm going uphill, but it can also happen when I'm pulling out on a straightaway. I'll be accelerating to get in front of someone, and once I reach my desired speed, I'll let off the gas and coast a bit, and when I go to accelerate again, Ill get the bump, bump bump. Let off the gas and give it a second, and then it goes away.

Here are things that I have replaced, some of which were for other issues, but in hopes that it would fix this problem too:
TPS
IAC
Fuel Pump
Injectors
All Mounts (engine and trans)
New driveshaft U joints.
Transmision Fluid level right at the full mark

As you can see, I was wondering if it could be a fuel issue. I'm aware that failing fuel pumps can cause jerking going uphill. Didn't make any difference in my case.
I'm skeptical, but I haven't done a tune-up in about 5 years, but this Jeep hasn't been my daily during that time. Would failing distributor, plugs, or wires really cause this type of symptom?

Of course, I have been wondering about the Transmission. Other than the fluids and filter, I haven't done anything to it.

Well, that's all I got for now. Really just looking for some direction. And some expertise!

Thank you all.

 

We have a 2001 cherokee and it does the same thing. Have replaced the TPS and all throttle body sensors twice. Good for a few days and then it was back. It shakes real fast and then goes away when I let off or go down hill. Going back to giving it gas it shakes again and then stops. The bigest thing I notice is it feels like the rear was hitting me from behind and then that stops but keeps coming back.?
Also replaced plugs, injecters to 4 hole one but no change., have done the touching bat cables together for 3 minutes and codes go away but come back.
It keeps throwing Codes
158
161
442
Next want to try replacing CPS and Cam sensor.
Dave

 

Hey Dave, yea I'm not sure it's the same exact issue I'm having but does sound close, so it could be!

I've already changed my CPS but not the camshaft sensor yet.

 

@Scooterpookin Have you checked for codes? When you did the pump, was it just the pump or the entire assembly? Was the tank clean inside? What injectors did you buy?

@Dave2001XJ Did you drop to "P0" in front of those codes? If so, the P0158 and P0161 are both O2 sensor codes for Bank2 sensor 2. (rear bank, after the cat). Check the harness to make sure it didn't hit the exhaust manifold. The P0442 is an evap code.

 

Yes thanks I know what the codes are and have replaced the 02's and check the 442 by plugging off the pump. It didn't change it so went to the can in back and have found 1 line that has a connector that has split and will repalce it. The rest is I think the CPS and cam sensor. I am 72YO and it is hard for me to lay down under car to put in the CPS so may just cut hole in floor to go through and replace.

 

Well this is interesting haha

Um yea it was the whole assembly and I made sure the tank was clean. I'm running bosch injectors. But this was happening before all of the repairs I've made. And after hasn't made any impact on the jerking. I'll post some codes soon.

 

When you changed the transmission fluid and filter, was that the first time it had ever been changed or after a very long interval? I ask because I had a '97 that acted similar all the sudden after its first trans fluid/filter. The fluid that came out was near black and I'm certain it was the first change the vehicle ever had. Was about 95k miles on it when I changed it.

I was telling a buddy of mine at work about the jeep jerking (similar to your description) and the condition of the trans fluid. He said something about build up in the torque converter causing the issue and told me to buy this little red tube of stuff from NAPA, in the moment he couldn't remember what it was called but assured me they would know what I was talking about. Turns out it was "Dr. Trannys Instant Shutter Fix". I squirted it into the transmission tube before I left the parking lot. The jeep never jerked again. It really was an instant fix for whatever was wrong with mine. I had that jeep until it got to about 225k miles and changed the transmission fluid and filter every ~40k or so and never had the problem again.

The root of your problem may be different but for a $10 bucks you could give it a try and see.

Good luck!

 

Since you’ve ruled out fuel, mounts, and throttle sensors, focus on these next:

- Ignition: Old plugs/wires or a weak coil can cause misfires under load (especially uphill). Swap them cheap and easy.
- Transmission: Slipping torque converter or worn solenoids can cause surging. Check for codes, even if no CEL.
- O2 sensors: A lazy upstream sensor can mess with fueling during acceleration. Scan live data or replace if old.
- Exhaust restriction: A clogged cat can cause bucking under load. Check backpressure or temp before/after the cat.

Try unplugging the TCC solenoid (if auto) to see if the surging stops a stuck torque converter clutch can mimic your symptoms.

 

Hello!

Thank you for all the suggestions. I will look into them and report back as I go. I finally got a decent enough code reader that is able to delete old codes. And just a quick drive to the store and back it did the same jerking and here's what popped up:

P0500
Vehicle speed sensor A

P1391
Loss of Cam or Crank

And of course P1493
Battery temp sensor ( which I keep saying I'm going to fix)

Well those first two sound promising, I've replaced the crankshaft sensor but not the camshaft.

I'm not sure which speed sensor A p0500 is referring to. But I have a whole post about discovering why speedometer doesn't work. I have a RWD and the speedometer drive gear which is plastic broke. So that could explain the p0500 code.

https://www.cherokeeforum.com/f2/no-...so-far-274940/

 

That's a great suggestion, I have done 2 fluid changes with a flush and one filter change since I've owned it. The last being just about a month ago. Fluid ran out clear. But like you were saying perhaps it is stuck up in the torque converter. Might be a good idea either way!

Thank you!

 

Now that you have the codes pulled you are on track. The P1391 is probably the majority of your issue. For Crank or Cam sensors I would try to find OEM if possible or a brand known to be a good solution. Others more knowledgeable than me have said that aside from Mopar the next best brands are NTK or Standard. Good luck!