Help with RPM jumping issue - 99 cherokee
02-21-2018, 01:31 PM
#1
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Model: Cherokee(SJ)
Help with RPM jumping issue - 99 cherokee
AS OF March 27th 2018 this has been RESOLVED - Issue was o2 sensor (Upstream) read on for the fun times!
I'm having some trouble and could use some help with where to look next.
I'm new to working on vehicles but enjoy the learning process and the wealth of info out there. What I've done so far: New Mopar TPS and CPS, New Plugs/Wires/distributor rotor and cap, new IAC valve, cleaned the throttle body completely.
The vehicle is my 99 Cherokee XJ, 148k miles. I cant drive it right now because of this issue.
The problem: when I accelerate from a stop sign the RPM's start to jump up and down like crazy.. this causes the vehicle to start bucking/jumping.
Here's a video: https://www.dropbox.com/s/ywsr4owjgl...51.11.mov?dl=0
If you watch the RPM's they are moving around like crazy. This actually makes the whole vehicle jump or buck forward and backward. The problem lasts for awhile and sometimes I hear a loud pop noise and it starts to drive smoothly. Other times I have to pull over completely and wait a bit, then I can drive again and the issue is gone.
Any ideas for me?
I'm having some trouble and could use some help with where to look next.
I'm new to working on vehicles but enjoy the learning process and the wealth of info out there. What I've done so far: New Mopar TPS and CPS, New Plugs/Wires/distributor rotor and cap, new IAC valve, cleaned the throttle body completely.
The vehicle is my 99 Cherokee XJ, 148k miles. I cant drive it right now because of this issue.
The problem: when I accelerate from a stop sign the RPM's start to jump up and down like crazy.. this causes the vehicle to start bucking/jumping.
Here's a video: https://www.dropbox.com/s/ywsr4owjgl...51.11.mov?dl=0
If you watch the RPM's they are moving around like crazy. This actually makes the whole vehicle jump or buck forward and backward. The problem lasts for awhile and sometimes I hear a loud pop noise and it starts to drive smoothly. Other times I have to pull over completely and wait a bit, then I can drive again and the issue is gone.
Any ideas for me?
Last edited by sotu; 03-27-2018 at 07:29 PM.
02-21-2018, 01:58 PM
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
Let's clarify - does this seem like it's the engine out of whack or the transmission can't figure itself out? It kind of appears transmission related from the description and video. If you pop it into neutral when it's happening, does it stop?
02-21-2018, 02:25 PM
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I'm not sure how to pinpoint engine or transmission as the source. It doesn't feel like a "shifting" issue because it starts from stopped - I'd assume that means it's in first gear the whole time, but maybe it's trouble going between 1 and 2?
02-21-2018, 02:26 PM
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02-21-2018, 03:00 PM
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
When you are having the issue, and you put it in N, if you give it gas does it smoothly increase or is it choppy?
I'm no expert, especially of Automatic Jeeps (all of mine were or are manual), but it seems suspiciously like an issue with the shift solenoids (I think one is for 1 & 2 which would be suspect 1) or TCU where the tranny can't figure out where to change gears... especially if it's bad in 1 & 2 and drives normally in 3 or 4.
I'm no expert, especially of Automatic Jeeps (all of mine were or are manual), but it seems suspiciously like an issue with the shift solenoids (I think one is for 1 & 2 which would be suspect 1) or TCU where the tranny can't figure out where to change gears... especially if it's bad in 1 & 2 and drives normally in 3 or 4.
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02-21-2018, 03:45 PM
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When you are having the issue, and you put it in N, if you give it gas does it smoothly increase or is it choppy?
I'm no expert, especially of Automatic Jeeps (all of mine were or are manual), but it seems suspiciously like an issue with the shift solenoids (I think one is for 1 & 2 which would be suspect 1) or TCU where the tranny can't figure out where to change gears... especially if it's bad in 1 & 2 and drives normally in 3 or 4.
I'm no expert, especially of Automatic Jeeps (all of mine were or are manual), but it seems suspiciously like an issue with the shift solenoids (I think one is for 1 & 2 which would be suspect 1) or TCU where the tranny can't figure out where to change gears... especially if it's bad in 1 & 2 and drives normally in 3 or 4.
Dang, just went on RockAuto and saw these are 100+ each? It looks like there's different ones for different shifting points.. looks like I can test it following this thread
Last edited by sotu; 02-21-2018 at 03:51 PM.
02-21-2018, 10:16 PM
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02-21-2018, 11:36 PM
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Have you tried pumping the pedal a few quick times and then stepping on it? If it clears up and takes off like a bat out of hell then it could be an O2 sensor problem.
02-22-2018, 09:46 AM
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2. I dont know this but I will check
3. I have not but will check this also.
How do you recommend I check #2 and 3? (will look on youtube)
My next steps:
Test Shift solenoids with Multimeter and if bad replace the ones that are bad.
Test Fuel Pressure.
Compression Test
Last edited by sotu; 02-22-2018 at 09:55 AM. Reason: update with next steps