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Unread 01-21-2009, 10:29 PM   #1
99sajeep
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Need to figure out stutter while driving

Ok, here's the deal.

My Jeep has what I call a "stutter" while driving down the road. Only happens between 60 & 75 mph. Mostly happens while in 4th gear (automatic) while climbing slight inclines like an overpass or small hill. The Jeep has a slight jerkiness to it (off and on) when applying 1/8 to 1/4 throttle, just enough to maintain speed. Will sometimes happen in 3rd gear (with O/D off), but mostly in 4th. If it down-shifts, the stutter goes away. It does not happen on a consistent basis or in any other speed range or gear.

My first thought was a transmission issue so I had the tranny flushed. Full fluid flush with filter and gasket change. No effect. I mechanic friend suggested it seemed like a fuel issue, like the filter was glogged slightly and could be starving the engine enough to cause the stutter. It was also suggested maybe an ignition miss?

I'm looking to see if anyone has a suggestion or any ideas as to what the problem may be. This is my daily driver that is used for work and I do a lot of driving (24k miles in less than 9 months).

I love my Jeep. It's definitely way more comfortable and better to drive than the 2 previous Exploders we had. Any ideas?

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Unread 01-21-2009, 10:42 PM   #2
Bannonjr
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I had this once on a for ranger...exact same thing....although your reason might be different...but it turned out to be the u-joints in the rear driveshaft,...

maybe it'll help?
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Unread 01-22-2009, 07:14 AM   #3
ratmonkey
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it's the torque converter not knowing the locking position it needs to be in. it is usually the tps or a transmission speed sensor.
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Unread 01-22-2009, 08:07 AM   #4
wsar10
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does the engine cut out a little (as if loosing fuel or spark) or stay the same throughout the problem? The reason i ask is becuase my jeep did this exact same thing when i bought it and i thought it was fuel pump or in the tranny, but turns out it just needed plugs and wires, i had a spot where the insulation on a plug wire was broke and the spark was jumping to my block under load. I had my fiance start the jeep while i looked under the hood and it lit up like a X-mas tree, thats how i found the problem.
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Unread 01-22-2009, 01:55 PM   #5
99sajeep
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Quote:
Originally Posted by ratmonkey View Post
it's the torque converter not knowing the locking position it needs to be in. it is usually the tps or a transmission speed sensor.
So if it is a tranny speed sensor, then replacing the input & outputs speed sensors should fix the problem? I read about the problems with those in another thread when I was researching this problem. I believe I read those are about $40 a piece at the dealer. Is that correct?

Even after the last two days, it still acts up, but not any more than it was before.

I will be checking the plugs and wires this weekend as I need to do that no matter what (too many miles on someone else's parts - never know what you have to work with). I may also look at replacing the fuel filter/regulator.

One step at a time I guess....
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Unread 01-22-2009, 02:01 PM   #6
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I had a very similar issue. When travelling along at constant highway speed I had periodic hesitation in the driveline. Very subtle, but noticeable none the less.

It went away after I replaced my (failed) tranny input speed sensor.
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Unread 01-22-2009, 02:06 PM   #7
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Is there anyway to test the speed sensors before replacing them? Just so I know that I'm replacing a failed part. I hate spending money on parts that don't fix the problem. I can always find a way to justify the expenditure in my mind, but trying to sell it to the wife may be a different story.
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Unread 01-22-2009, 02:24 PM   #8
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You did not mention whether or not you are getting a check engine light! If you are try running the problem codes by turning the key to on and then to run 3 times in a row. the third time leave in run position but do not start the vehicle. check speedometer for codes! If no check engine light don't bother running engine codes as they will not show up anyway. Look at mechanical problem or fuel problem as a sensor problem should light up check engine, you hope! Good Luck!
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Unread 01-22-2009, 05:13 PM   #9
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Quote:
Originally Posted by 99sajeep View Post
Is there anyway to test the speed sensors before replacing them? Just so I know that I'm replacing a failed part. I hate spending money on parts that don't fix the problem. I can always find a way to justify the expenditure in my mind, but trying to sell it to the wife may be a different story.
Test the contacts with an ohmmeter. If they read open, they are no good. Though in your case you may get a reading b/c your's haven't failed completely. In my case, my tranny went into limp mode and I had the P0700 code, but once I replaced the sensor all was well again and the hesitation was gone.
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Unread 01-22-2009, 05:22 PM   #10
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The canuck is dead on..... again

read a similar post from me...with testing info. http://www.jeepforum.com/forum/f13/speed-input-output-sensor-failure-561977/
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Unread 01-22-2009, 05:28 PM   #11
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So far, no codes have been thrown. When I check, it just says "done."
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Unread 02-10-2009, 11:35 AM   #12
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So now for an update:

On the 24th (Jan), I pulled the plugs and they we worn down to almost .075"!!! So that pretty much was my problem. Both tranny sensors checked out ok and the Jeep was running fine.

Until...

This past week, as I was driving home on Thursday (2/5), I was slowing down for traffic when, "wham!" I thought I hit something, but then noticed I was in 3rd gear. From that point on, the tranny didn't seem quite right. It would go into all 4 gears, but it shifted in all the wrong places. 4th gear wouldn't happen until after 60 mph and when slowing down below that, it would slam hard into 3rd gear. Check Engine light was now on and it threw the P0700 code.

I pulled both sensors, and checked them with an Ohm meter. The rear sensor showed nothing. The front one had a reading. Picked up a new sensor and put it in the rear position and everything is running fine now.

How strange that the one sensor would go out like that just shortly after I thought that was the problem to begin with!

Anyway, we're up and running fine for now. I expect to have the other sensor good bad anytime, but unfortunately I didn't have the cash to just go ahead and replace it. If it does go out, I have a wrench and something to lay down on and can change it out in less than 5 minutes; in case I need to change it while on the road. I do a lot of driving...

Thanks for all the help.
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