Daniel Sims

First post. Sorry if it's in the wrong place or bad formatting. On mobile.
2000 Cherokee xj 245k, engine is freshly rebuild (piston slap in the old on) trans has 136k. I've tried everything(Almost everything). So after driving for about 30 minutes at highway speeds the rpms flutter and then it feels like the trans tries to downshift. rpms jump up about 500ish for a second or two and then jolts back down into overdrive. It does it when my foot is light on the gas.
Again, only does it at highway speeds after fully warmed up. Coolant stays @ 190-210
Thought it was torque converter so I replaced it. Still jolts. Thought it was trans so I put a different trans in. Still jolts.
replaced crank sensor, cam position sensor, coil pack and plugs. New iac, cleaned throttle body. Alt is new, battery is fairly new.
It's not throwing any codes. My next step was going to be fuel pressure test and either new injectors or a heat shield around fuel rain and injectors. Maybe they are getting heat soaked? Or maybe my fuel pressure is getting interrupted somewhere? This afternoon I'm going to check my grounds and clean connectors. Could it possibly be a fault in the pcm? I'm at a wall. With it not throwing any codes I don't really know where else to check.

Any suggestions or advice would be helpful. Trying to take a trip from tn to AZ at end of May but not if it's going to leave me stranded somewhere.
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Daniel Sims

Also maybe throttle position sensor? Could that be a culprit?

tballer4596

Before reading through your whole post I was ready to blame the CPS. I see you said its new, but I do have to ask which brand it is. While my issue was not exactly the same, I was experiencing jolts on the highway where the entire engine would die for maybe half a second and come back with a jolt. It happened fast enough that it seemed to me like a misfire, not a complete engine cut. Just a big jolt. I blamed fuel pump, injectors, blah blah blah. Turns out it was the "brand new" CPS I had installed a couple weeks prior. I went with the $15 version and that's what I get. I've since installed the crown auto version with no problems.

Now, there's also every chance that's not the issue, since the rpms shooting up isn't familiar to me for this issue. I'm unclear if you changed the CPS since the issue started or before, but if it was after the issue started and the issue still persists, there's less chance of the CPS being the problem.

I'm not sure I would blame heat soaked injectors. At highway speeds you have tons of air flow into the engine bay, and heat is far less likely the issue. If the issue presented itself after letting it sit for a few minutes and then starting it up again, I might blame the injectors.

Because the RPMS are jumping around it sounds to me like it has something to do with the computer or the trans. This may be a stupid question, but have you adjusted your trans cable? It takes 2 seconds and could have something to do with it, but I dont have much experience with trans issues. You should also check your throttle position sensor. If you have an OBD2 monitor, pull up a graph of the throttle position sensor and wait for the issue to happen. You should see a dip or a spike if the TPS is in fact the issue. Hopefully it is because thats an easy fix.

Daniel Sims

I installed a new cam sensor before and the crank after. I'm not sure of the brand I got. It came from O'Rileys but I'll look into getting an OEM cam sensor. Mopar I believe, right? I do have an obd2 but I'm not sure of the graph you're talking about. I'll do a little research and find out though. I will adjust the trans cable and see if that has anything to do with it.
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tballer4596

So on my OBD2 app (its called car scanner) I can pull up the list of all available sensors in the truck. If I click on the throttle position sensor, it pops up a line graph over time of the throttle position. So you can see in real time what the throttle position sensor reading is. So theoretically, if your TPS is acting up, you'll see either a big dip or a big spike on the graph (indicating your tps is telling your motor either you let go of the throttle completely or you are flooring it). If the issue persists with no noticeable weirdness on the TPS graph I think we can eliminate the TPS at that point. As far as mopar for the CPS, everyone says you must go mopar, but of cours its big bucks as we know. I went with the crown auto since I've had good luck with their OEM parts before and it was about $45 if I remember. Whether that was risky or not, I cant say. Some people swear by crown, some people say MOPAR only. All I can say is it fixed my problem for sure.