96 ZJ limited 5.2 rpm fluctuation - JeepForum.com
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post #1 of 10 Old 05-29-2020, 07:12 PM Thread Starter
ZJJeepers1972
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96 ZJ limited 5.2 rpm fluctuation

Hi guys

My Jeep has done this before but only a short period one day. But beginning yesterday till now its constant and it seems to be drinking way more gas.
As im driving along at a steady speed the rpms will jump 250 rpms and then back down to normal and then maybe 5-8 seconds later it does it again. Also you can be rolling along with your foot off the gas and it will do the same thing for a couple of times.

Thank you guys for any information you can provide on this.

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post #2 of 10 Old 05-30-2020, 05:50 AM
V8GCZJ
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When driving it could be the lock up solenoid kicking in/out but in park it's something else. Do you have any codes? Constant fuel pressure?



https://www.quadratec.com/jeep_knowl...article-24.htm
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post #3 of 10 Old 05-30-2020, 06:46 AM Thread Starter
ZJJeepers1972
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The check engine light is not on. It doesn't do it in park. It only does it when driving.
Would the lock up sensor make the rpms jump even when you're coasting with no throttle?
I haven't checked the fuel pressure.
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post #4 of 10 Old 05-30-2020, 08:32 AM
jeepjeepster
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I do believe a bad TPS can cause the rpms to fluctuate even when off the throttle and it may not cause the check engine light to come on. I recommend a mopar unit, not aftermarket.

You can check the TPS with a multimeter to see if its putting out any wild voltages while slowly moving the throttle by hand.

1994 ZJ-I6 w/270,000 mi
1998 ZJ 5.9 w/66,000 mi Slate Black
2004 KJ w/108,000 mi
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post #5 of 10 Old 05-30-2020, 09:01 AM Thread Starter
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I have another jeep. I'm heading there now to remove some parts.
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post #6 of 10 Old 05-30-2020, 11:35 AM Thread Starter
ZJJeepers1972
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Check engine light is on and it is now throwing p0123 and p0720.
OD is not working and cruising along if you let off throttle it goes in to neutral and you have to give it a CPL seconds to go back in gear.
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post #7 of 10 Old 05-30-2020, 03:29 PM
riiz
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Check out the TPS first, do a voltage sweep and/or inspect the harness. The second code is a transmission speed sensor fault. the plug for that is located on the rear of the transmission, driver-side. Check to see if you have continuity between both pins on that sensor. A bad TPS or Speed Sensor will cause the same rpm/tranny problems, grab a mopar sensor if you decide to throw a part at it.

MOPAR 68405575AA - TPS

MOPAR 4800879 - Speed Sensor
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post #8 of 10 Old 05-30-2020, 08:11 PM
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Garage
Not sure how long its been but I would also sugest making sure your throttle body is cleaned..
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post #9 of 10 Old 05-31-2020, 08:26 AM
V8GCZJ
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P0123 Throttle Position Sensor #1 Voltage High
P0720 Output Speed Sensor Error
This should explain it.
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post #10 of 10 Old 06-01-2020, 03:35 AM Thread Starter
ZJJeepers1972
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Ok guys. Sorry it took so long for me to get back to you but it did turn out to be the TPS.
Thank you guys for all your help and Information.
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