jowint

Over the last 2 weeks I've noticed while cruising in 4th gear (usually when behind a slow poke) the engine will buck until Press the gas to upshift then its smooth.
it will usually cruise fine and not buck in fourth if I have it under a decent load but if I'm cruising in 4th say up a hill at a slower speed at the point where it should kick down on its own it will buck until I hit the gas and upshift.
i also noticed the other day during start up that it seemed to buck for a second while cranking like it was going to fire but didn't then did all of the sudden.
no CEL.
No codes found.
Has a one year old tune up including cap, rotor, coil, plugs, wires, upgraded battery cables and two new grounds from battery (-) to chassis and battery (-) to block.

Ive had CRank pos sensors go on me before but the bucking was under load almost always and never got better with upshift but I carry a spare just in case.

just a note ....it almost seems like a throttle position sensor issue and I had replaced one years ago due to bucking and a hard code it threw for TPS but ever since I replaced that TPS years ago the kickdown was never as immediate or as responsive as the old sensor.
i had to almost manually make it kick down by depressing gas pedal further but never had issues until this recent problem.

Tbone289

I assume you mean downshift to third here, right? You can't upshift from 4th--4th is top gear.

Mine does something similar. If I'm going up a steep hill and keep pressing the gas farther down to compensate for speed loss, if I press it down to the point just before it shifts down to 3rd--but not quite that far--it will "jerk" slightly, and feels like an ignition miss. It usually does this just once for a split second, and I always assumed it was the TPS reading "wavering" slightly in that range and thus the PCM briefly gets confused as to the position.

When you replaced your TPS, did you replace it with a Mopar part, or aftermarket? Mopar sensors will generally operate better and last longer.

jowint

Yeah downshift, sorry.
i replaced it with a cheap part, not Mopar and regretted it from the start but it still ran fine other than it wasn't as responsive.
i may order a Mopar TPS and try it out.

wondering if my throttle valve cable might need adjusted.

Tbone289

It certainly wouldn't hurt to adjust the TV cable. It's very easy to do, but it hasn't helped my issue.

TV cable adjustment:

https://www.cherokeeforum.com/f5/kic...ustment-95421/

There are also test procedures you could use to test the function of your TPS rather than just replace it.

fb97xj1

jowint

I adjusted the TV cable and it took a little slack out of the cable but still did not help my problem.
i ordered a genuine Mopar TPS- should be here next couple days.
checked my current TPS voltage.
.78 v at rest/ 3.1v WOT with no erratic jumps during sweep of throttle blade.
Im confident the new TPS will fix it....will update as soon as I find out.

jowint

I replaced the TPS with a genuine Mopar part, and the problem still exists.
trans fluid at full hot mark when hot

97grand4.0

If you never replaced the AW4's solenoids, you should. Can get all 3 on the net for under a buck. Do a fluid and filter while there. Did it, its not hard if you prepare for it. That tranny is a rock, all I needed ever to do to it.
A note on the TV cable, Ive read all the articles etc. If you high miler what works best for me is adjust it to the stock setting per instructions, then tighten it up juuuuust about 1/8 inch more, like a match head width. Seems to be the sweet spot. The line pressure is increased to compensate for your leaking internal seals. My dirty garage trick. Go too far tho and you will notice increased rpms for a shift point and a rougher shift. Your goal is the smoothest shift you can get, not any rpm target.

Also invaluable is a cheap scan tool with graphing, can watch the tps and other inputs real time. no better way to see if they work right. I just had a box store tps go bad after about 2 years, it would go through the range fine with no blips, but at idle you would see it spike down all the sudden for no reason. Replaced it with a junkyard mopar and smooth as heck and much better idle and performance and even shifting.

00t444e

Mine sometimes boggs down on the 1-2 shift. I have adjusted the Tv cable and the fluid is good so I think it may be a TPS issue. It doesn't do it very often so I don't worry about it to much.

jowint

I've got a scan tool but no graphing.

i had changed my trans fluid and filter
about three months ago and my problems are getting worse now.
Not only is the bucking still there but I am now getting some misfires or popping/ skipping under load in any gear and crappy idle cold that feels like idle air control dirt.
Under load it feels like your typical Crank sensor issues so I replaced it with a knock off spare I keep in the glove box.....problem still exists and no darn codes or check eng light.
Coil is less than a year old but I inspected it anyways....it's fine.

Gonna check my cap/ rotor/ plugs/wires.

BTW jeep has 260,000
miles on it.

coolant fine, fuel pressure fine, oil looks good, engine has a bit of a knock but has for years and it hasn't gotten worse.
I'll do a compression test just for the sake of it.
Ill report back soon.

jowint

Since I started having the stumbling/ skipping issues I decided to run the engine last night in the dark and spray all the ignition wires with a spray bottle of water.
i noticed #5 wire was arching on the dipstick tube and found a burn spot there.
i decided to replace the ignition wires and went ahead and put in new plugs, cap and rotor as well.
immediately upon start up the engine purred like a kitten.
no skipping under load and no more bucking before shifts.
ran like a champ with tons of power.

looks like it was taking the path of least resistance and bucking on low RPM between shifts and would get better spark and clear up under heavier throttle and spark demand.....makes sense.

I'm kinda glad it started skipping and popping under load in any gear and the idle got worse which led me to investigate ignition wires.....stick a fork in it.