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-   -   98 TJ comes to a stop after 30min at highway speeds (http://www.wranglerforum.com/f210/98-tj-comes-to-a-stop-after-30min-at-highway-speeds-75692.html)

pinkdestruXtion 01-13-2011 12:36 PM

98 TJ comes to a stop after 30min at highway speeds
 
I have a 98 Wrangler Sport, manual transmission. When driving at highway speeds for 30+ minutes the vehicle will hesitate slightly, lose power and coast to a stop. It feels like it has run out of fuel however, the RPMs do not drop until I remove my foot from the gas pedal. It generally does not stall out, it just comes to a stop. After waiting 5 minutes the jeep will drive again with no problems for another 30+ minutes. So far this has not happened at lower speeds, only 70mph+. The issue is sporadic and does not occur everytime I drive the vehicle, but it is frequent.

More details:
  • The check engine light does not come on.
  • It's not throwing any codes.
  • I've had the fuel pressure tested (not while the problem is occuring) and the pressure was fine.
  • The cat. converter was recently replaced.
I've read other similar forums talking about fuel pump/filter, o2 and TPS sensors and/or vacuum leaks. What strikes me as different about my situation is the fact that as long as my foot is on the gas the RPMs do not decrease as the spedometer decreases. The jeep is in 5th gear and the rpms remain strong at 3000rpms or so yet it just slows down like it isn't getting fuel. I'm thinking if it wasn't getting fuel would the RPMs would also decrease but I'm no mechanic. Thoughts?

Black98 01-13-2011 12:44 PM

are you sure the engine is still running at 3k and the tach is not actually stuck or something? And if the tach is right it sounds like something in the drivetrain is starting to lose connection somehow like a clutch or something wearing out in the T-Case and or Transmission causing the power to no longer make it all the way to the rear wheels

pinkdestruXtion 01-13-2011 12:56 PM

Thanks. Yep, defintiely sure the engine is still running. As soon as I take my foot off the gas pedal it will start to decrease. If I put pressure back on the gas pedal the RPMs go back up, but the jeep continues to lose speed.

Jerry Bransford 01-13-2011 01:29 PM

My first guess is that the crankshaft position sensor has become intermittent, especially that you have already verified that the fuel pressure is okay. The crankshaft position sensor is what provides the engine its master timing signal. When it stops sending its signal out, the engine dies.

Plowboy1970 01-13-2011 03:01 PM

So, what you are saying is you keep your foot on the gas and it still shows 3000 rpm's but the jeep comes to a standstill but is still running 3000 rpm's?????????? You say the rpm's don't move?????? Just the mph slow down???

pinkdestruXtion 01-13-2011 03:13 PM

Correct. I don't actually keep my foot on the gas the whole time the vehicle is stopping (seems pointless since it doesn't regain power) however, I have tried downshifting as the vehicle slows and stepping on the gas again. The enging revs, the RPMs increase but the jeep gets no power. It only regains power after I've pulled over and let it sit for a few min.

Plowboy1970 01-13-2011 03:27 PM

Quote:

Originally Posted by pinkdestruXtion (Post 987218)
Correct. I don't actually keep my foot on the gas the whole time the vehicle is stopping (seems pointless since it doesn't regain power) however, I have tried downshifting as the vehicle slows and stepping on the gas again. The enging revs, the RPMs increase but the jeep gets no power. It only regains power after I've pulled over and let it sit for a few min.


That sounds like it would be your clutch??? Is it slipping???? Sounds like your pressure plate is going.

pinkdestruXtion 01-13-2011 03:36 PM

The clutch seems to work fine when I'm shifting through the city, I've never had any issues with that. This problem only occurs when the jeep has been in 5th gear at 70+mph for approx 30 minutes, then all of a sudden it will just start slowing down. Would that still be a clutch issue?

Plowboy1970 01-13-2011 03:51 PM

Quote:

Originally Posted by pinkdestruXtion (Post 987266)
The clutch seems to work fine when I'm shifting through the city, I've never had any issues with that. This problem only occurs when the jeep has been in 5th gear at 70+mph for approx 30 minutes, then all of a sudden it will just start slowing down. Would that still be a clutch issue?


If engine rpm's stay up but speed decreases. Something is disconnecting the engine from the drivetrain. So, when this happens, and you stop. Can you put in first and let the clutch out like normal and rev the engine up and push the clutch in and shift to second and release the clutch and rev it up too and not move at all?????????????????? If so, I would say your pressure plate is junk. Probably getting hot and loosing spring pressure and when it cools it locks and works????

pinkdestruXtion 01-13-2011 04:10 PM

It's been a while since I've actually tried revving it up from a complete stop before its sat for a few min (since it wouldn't go anywhere the first few times I tried that). I will try again and make sure that is still an issue. I do know that as it slows, even to 5 or 10 mph, I consistently down shift, put it in 2nd and push on the gas and nothing ever happens - it just stops. Thanks for your post, I will update this if anything changes after it happens again (usually every couple days or so).

Jerry Bransford 01-13-2011 06:18 PM

So the engine never actually stops? I read your first post and interpreted it to be saying the engine was actually dying.

pinkdestruXtion 01-13-2011 06:44 PM

No, the jeep doesn't actually stall/die...it's almost as if someone threw it in neutral as I was driving down the highway. It just coasts until it comes to a stop but never actually stops running.

footbal9584 02-26-2011 08:22 AM

Hi, did you ever figure this out? I literally just started having the same problem but it's with a 2000 Jeep Grand Cherokee 4WD. First it takes a little effort to get it going from a stop. Then it seems like it will just randomly "slip into neutral", and the engine will keep going but the wheels lose power. Mine, though, doesn't happen after a prolonged period of time, it will happen within a few minutes of starting, normally while accelerating to get on the highway. I don't have to let it sit or stop, it just jumps back into gear after a few seconds and I can keep going.

rafipmk 06-17-2013 01:36 AM

Dear All ,
I have the same problem. I did one full water service on my Wrangler TJ yesterday evening, after that when I shifting the gear the rpm does not decrease when I remove my foot from accelerator. And when I put the gear in neutral the engine is sound like it going to off ( rpm reducing ) and suddenly its rpm get increasing. I don’t know what’s wrong


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