Hesitation or Stuttering around 40-50MPH. Bout to sell the thing

Blunt

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Hi all. I’ve been lurking this forum for a while and tried to read every forum post related to this problem I’m having. Unfortunately I’m still at a loss for answers and I am darn close to rolling her down the quarry lol.

I’ve had this 2004 3.7L Jeep Liberty 4x4 w/automatic transmission for over 6 years at this point. Currently at 177,000miles! Besides regular maintenance she has been one of the most reliable vehicles I’ve had. Until now.

(For those who don’t want to read entire post I have a hesitation or stutter when accelerating around 40-50mph)

For those who want to know more. I had gotten a new daily driver and let the Liberty sit for almost 8 months. My wife was out of a vehicle so I let her drive the liberty. Everything was fine except it was taking a while to start. This is where the problems begin. One day while my wife was leaving work it refused to start and it was obvious it needed a starter. Luckily she worked next to a mechanic and we had him install a remanufactured starter and we were back in business. Not long after the battery began to get very unreliable sometimes needing to be jumped after a couple days of sitting. Figured it was from the excessive cranking when we had a bad starter. Also at this time the jeep would buck really bad and we had a code for bad transmission range circuit or sensor. Replaced the battery and all lights went away so I figured the code was due to low voltage. Shortly after this I bought my wife a new daily and once again parked the Jeep (probably 3 months). Now we are up to date I recently needed to use the Jeep for work. I noticed it was running terrible and developed a really bad hesitation when stepping on the throttle at any RPM. Felt like multiple misfires and confirmed this by reading the codes. Changed all the spark plugs and the CEL went off. Started the Jeep and it never idled so smooth before. Took it for a test drive to confirm it was fixed and I was happier than a kid in a candy shop because it drove better than it ever did in my 6years of ownership but that was short lived as after about 15 mins of driving, once the motor fully warmed up the hesitation was back. But this time it didn’t throw any codes. I figured I had maybe the wrong gap on the spark plugs so took them all out and gapped them to Manufacturer spec and once again reinstalled them. As I was reinstalling I noticed two sensors just completely snapped just holding on by small electrical connections. The TPS sensor and the AC pressure transducer. Now I’m a mechanically inclined DIY’er but this next part is what stumps me. I temporarily mended the broken sensors back together making sure all connections were intact to make sure this was the problem. I found it weird that it didn’t throw a code but was curious. Took it for a test drive and it still ran poorly and hesitated on acceleration, I unplugged the sensor and took a test drive and it ran perfect like absolutely no acceleration issues, fuel economy I’ve never seen before I mean perfect only thing is it threw a code for missing TPS (obviously lol) so in my mind it was confirmed bad TPS, no problem Got the parts from autozone and within 15 mins had everything back together again cleaned the Throttle body while I was at it, go to Start the Jeep and it was running even worse but still no code. At this point I thought I installed incorrectly so I removed it and reinstalled. Same results. So then I tried to recreate the same thing I did with the old one by unplugging it and going again but this time I had no throttle response so it was impossible to drive. Did a hard reset on all computers, nothing. Fuel treatment. Nothing. Cleaned the heads with seafoam. Nothing. Then I saw a video about the relay for the fuel pump acting up when the engine was warm so I changed that relay as well as all fuses related to fuel pump and PCM. This made the hesitation MUCH better in low gears and speed but it still hesitated around 40-50MPH almost feels like a fluttering or dead-spot in the pedal. I checked the PCV and it was okay so I reinstalled it. I don’t understand why it drove perfectly that one time and I can’t recreate it now. Sorry for the rambled mess I am just so irritated. I’ve made a lot of memories in this Jeep and the last thing I want to do is sell it but I need a work vehicle and my patience is running thin on this. I’m probably missing a whole bunch of info forgive me as my brain is a scattered mess rn lol.
 
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LibertyTC

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Sounds like it does not like the autozone tps sensor.
Jeep only likes oem sensors so try a mopar Tps.
There is an alignment tab for the tps,
And trying to remember if you set tab into place and then move it slightly counter clockwise to screw it back in place.
Clear codes after tps install.
 

Blunt

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Quick edit: I confirmed the TPS was getting proper power voltage. Normally under these circumstances I’d look into normal causes such as Coils, Wires, O2 sensors, Injectors, Fuel pump/filter, etc. but it wouldn’t explain why there is no CEL and if any of the above was bad why would the vehicle run and drive perfect that one time with the TPS unplugged. I am truly stumped. And to make it worse I had to sell a bunch of my tools when I moved so I don’t have the same diagnostic abilities I once had.
 

Blunt

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Sounds like it does not like the autozone tps sensor.
Jeep only likes oem sensors so try a mopar Tps.
There is an alignment tab for the tps,
And trying to remember if you set tab into place and then move it slightly counter clockwise to screw it back in place.
Clear codes after tps install.
Thank you, I will order a Mopar sensor today and cross my fingers. I feared the TPS may be faulty but it was getting proper power voltage and resistance seemed normal. If the OEM sensor doesn’t work any other idea of what to chase down next? I really fear the PCM may be bad or even worse this is one of the “unfixable” horror stories I’ve read about with similar symptoms. Really crossing my fingers
 

LibertyTC

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Btw jeep likes NGK ZFR6F-11G spark plugs only. Misfires can be related to wrong plugs being used.
Do you have the NGK^ ^^ correct plugs installed ?
 

Blunt

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Btw jeep likes NGK ZFR6F-11G spark plugs only. Misfires can be related to wrong plugs being used.
Do you have the NGK^ ^^ correct plugs installed ?
I believe so but I will have to check when I get home from work. On my drive to work today I noticed it seemed to hesitate every time I shifted into highest gear. Really hoping it’s not the Torque converter. I checked my trans fluid and it was at the proper level and not abnormally dirty. Also tried unplugging my map sensor and although it seemed to have more pep it still hesitated around 40-55 mph
 

Bikeflyer

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Also having this issue, wondering after doing everything except a map sensor could the generic TPS be a thing? It goes away when I get out of that window of speed or push OD off. Could it be a thing like the TC engagement going wonky? Sure hope not but seen it happen on other cars.
 

BackRoadEnthusiast

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Hi all. I’ve been lurking this forum for a while and tried to read every forum post related to this problem I’m having. Unfortunately I’m still at a loss for answers and I am darn close to rolling her down the quarry lol.

I’ve had this 2004 3.7L Jeep Liberty 4x4 w/automatic transmission for over 6 years at this point. Currently at 177,000miles! Besides regular maintenance she has been one of the most reliable vehicles I’ve had. Until now.

(For those who don’t want to read entire post I have a hesitation or stutter when accelerating around 40-50mph)

For those who want to know more. I had gotten a new daily driver and let the Liberty sit for almost 8 months. My wife was out of a vehicle so I let her drive the liberty. Everything was fine except it was taking a while to start. This is where the problems begin. One day while my wife was leaving work it refused to start and it was obvious it needed a starter. Luckily she worked next to a mechanic and we had him install a remanufactured starter and we were back in business. Not long after the battery began to get very unreliable sometimes needing to be jumped after a couple days of sitting. Figured it was from the excessive cranking when we had a bad starter. Also at this time the jeep would buck really bad and we had a code for bad transmission range circuit or sensor. Replaced the battery and all lights went away so I figured the code was due to low voltage. Shortly after this I bought my wife a new daily and once again parked the Jeep (probably 3 months). Now we are up to date I recently needed to use the Jeep for work. I noticed it was running terrible and developed a really bad hesitation when stepping on the throttle at any RPM. Felt like multiple misfires and confirmed this by reading the codes. Changed all the spark plugs and the CEL went off. Started the Jeep and it never idled so smooth before. Took it for a test drive to confirm it was fixed and I was happier than a kid in a candy shop because it drove better than it ever did in my 6years of ownership but that was short lived as after about 15 mins of driving, once the motor fully warmed up the hesitation was back. But this time it didn’t throw any codes. I figured I had maybe the wrong gap on the spark plugs so took them all out and gapped them to Manufacturer spec and once again reinstalled them. As I was reinstalling I noticed two sensors just completely snapped just holding on by small electrical connections. The TPS sensor and the AC pressure transducer. Now I’m a mechanically inclined DIY’er but this next part is what stumps me. I temporarily mended the broken sensors back together making sure all connections were intact to make sure this was the problem. I found it weird that it didn’t throw a code but was curious. Took it for a test drive and it still ran poorly and hesitated on acceleration, I unplugged the sensor and took a test drive and it ran perfect like absolutely no acceleration issues, fuel economy I’ve never seen before I mean perfect only thing is it threw a code for missing TPS (obviously lol) so in my mind it was confirmed bad TPS, no problem Got the parts from autozone and within 15 mins had everything back together again cleaned the Throttle body while I was at it, go to Start the Jeep and it was running even worse but still no code. At this point I thought I installed incorrectly so I removed it and reinstalled. Same results. So then I tried to recreate the same thing I did with the old one by unplugging it and going again but this time I had no throttle response so it was impossible to drive. Did a hard reset on all computers, nothing. Fuel treatment. Nothing. Cleaned the heads with seafoam. Nothing. Then I saw a video about the relay for the fuel pump acting up when the engine was warm so I changed that relay as well as all fuses related to fuel pump and PCM. This made the hesitation MUCH better in low gears and speed but it still hesitated around 40-50MPH almost feels like a fluttering or dead-spot in the pedal. I checked the PCV and it was okay so I reinstalled it. I don’t understand why it drove perfectly that one time and I can’t recreate it now. Sorry for the rambled mess I am just so irritated. I’ve made a lot of memories in this Jeep and the last thing I want to do is sell it but I need a work vehicle and my patience is running thin on this. I’m probably missing a whole bunch of info forgive me as my brain is a scattered mess rn lol.
Had the same problem with mine, ended up just being a weak coil pack..
 

Bikeflyer

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I have the same thing on mine but hasnt changed with all new coils and plugs. It seems more Torque converter lock than loading. Just a hunch
 

Johnm

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If you can use a scanner live data check your oxygen sensors especially the upstream sensors can cause all kinds of problems and sometimes won't throw a code !
 

Ksat

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I second the live data suggestion. There's a wealth of information to be found in what you get from it. Specifically, it will tell you what your TPS values are, then you can compare that to what they should be. You'll get info from other sensors, as well, like the MAP.

Throwing parts at it in the hopes it gets fixed can get expensive (and frustrating) real quick.
 

Jeremy-WI

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If you want to eliminate the torque converter, just press on the brake pedal a bit when the problem occurs
 

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