91 xj 4.0 Shifts at 4k rpms TPS replacment
#1
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91 xj 4.0 Shifts at 4k rpms TPS replacment
Hi guys a little help here...
I just replaced my TPS and driving around every thing was going fine shifting normal
Stomped on the gas and took off as fast as I could, every acceleration after that shifts at 4k rpms even if i take off slow from a dead stop and drive 25 it goes to about 3.3k and does not shift, if i stomp on it will will go through all the gears but not shift untill 4k, could this be related to the "programing" of the new TPS?
Tried
Letting it sit for a day with the batt off
Key off - unplug TPS - key on 5 sec - key off - plug in TPS
I guess next move would be the kickdown cable? But that dosnt sound hopeful
Any input would be greatly appreciated thank you
I just replaced my TPS and driving around every thing was going fine shifting normal
Stomped on the gas and took off as fast as I could, every acceleration after that shifts at 4k rpms even if i take off slow from a dead stop and drive 25 it goes to about 3.3k and does not shift, if i stomp on it will will go through all the gears but not shift untill 4k, could this be related to the "programing" of the new TPS?
Tried
Letting it sit for a day with the batt off
Key off - unplug TPS - key on 5 sec - key off - plug in TPS
I guess next move would be the kickdown cable? But that dosnt sound hopeful
Any input would be greatly appreciated thank you
#2
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Year: 1999
Model: Cherokee
Engine: 4.0
1. It would be helpful to know why you replaced your TPS originally.
2. what brand of TPS did you install? There is a wide range of quality with this important engine management sensor. I favor installing genuine Jeep parts when it comes to the TPS.
3. Do you currently have a check engine light and if so, what are the codes.
2. what brand of TPS did you install? There is a wide range of quality with this important engine management sensor. I favor installing genuine Jeep parts when it comes to the TPS.
3. Do you currently have a check engine light and if so, what are the codes.
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1, I watched youtube videos of the symptoms of my rough idle foud the tps to be the cause when replaced it smoothed out the idle and stalling issues.
2, I replaced with the $23 one from 1AAuto, they also offered a $48 one, I might have to try a better quality one
3, No codes
4, Thank you for getting back so fast
2, I replaced with the $23 one from 1AAuto, they also offered a $48 one, I might have to try a better quality one
3, No codes
4, Thank you for getting back so fast
#5
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Year: 1999
Model: Cherokee
Engine: 4.0
Rough idle can be caused by a lot of things. A dirty throttle body, dirty idle air control, tuneup hardware needing to be replaced, internal engine issue, engine management sensors, the list is really quite long. Consider this a "process of elimination". It's not always straight forward and finding out what it ISN'T is often a big part of finding out what it IS.
When was the last time you installed new plugs, plug wires, distributor cap, rotor? Never underestimate the importance of a solid secondary ignition system and tuneup hardware is relatively inexpensive and easily installed. Champion plugs gapped properly, quality plug wires, cap and rotor. Don't buy cheap tuneup parts.
It's possible that the new TPS may have added an additional issue and that can confuse things even more. BTW, the TPS for 91-01 is not adjustable. If you do replace it, spring for a genuine JEEP one. The extra money is coin well spent. In the meantime, if things got worse after you replaced your old TPS, (if you didn't have that shifting issue) put your old TPS back on if you still have it. I'd rather have an old Jeep TPS than a new inexpensive one that doesn't play well with your engine and transmission. This is a very important sensor.
My recommendation is to replace all tuneup hardware if you haven't recently and perform the below cleaning procedure of the throttle body and idle air control. And maybe slap on that old TPS. Then see where you are at.
Another thing to consider. How many miles on the engine? Performing a simple compression test on all cylinders is also never a bad idea as it is a good "snapshot in time" as to the internal condition of your engine. The compression spec. for the 4.0 engine is 120-150 psi, with no more than a 30 psi variation between cylinders. You can rent a compression gauge from many parts stores very inexpensively; call around for availability. A weak cylinder can give you the symptoms you are talking about so don't ignore that possibility, especially for an engine with high mileage. I had one guy bring his XJ to me and he replaced every single engine sensor and most everything else he could get a wrench on but it still ran like crap. A simple compression test confirmed the internals in his engine were on life support. Tail chasing to be sure.
One final thing. Stalling at idle CAN be caused by a marginal battery. And yes, you can have a battery strong enough to start your engine, but marginal enough to cause stalling. Very common actually and I've seen it more times than I can remember. So have you battery "load tested". This service is free at any parts store. When available juice is low, your engine management system is not happy.
So that is exactly how I would approach it if your XJ was in my driveway. Good luck and keep us updated!
-----------------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.
CLEANING THE JEEP 4.0 IDLE AIR CONTROL
Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)
“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner
It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled
Reinstall IAC and check idle quality
When was the last time you installed new plugs, plug wires, distributor cap, rotor? Never underestimate the importance of a solid secondary ignition system and tuneup hardware is relatively inexpensive and easily installed. Champion plugs gapped properly, quality plug wires, cap and rotor. Don't buy cheap tuneup parts.
It's possible that the new TPS may have added an additional issue and that can confuse things even more. BTW, the TPS for 91-01 is not adjustable. If you do replace it, spring for a genuine JEEP one. The extra money is coin well spent. In the meantime, if things got worse after you replaced your old TPS, (if you didn't have that shifting issue) put your old TPS back on if you still have it. I'd rather have an old Jeep TPS than a new inexpensive one that doesn't play well with your engine and transmission. This is a very important sensor.
My recommendation is to replace all tuneup hardware if you haven't recently and perform the below cleaning procedure of the throttle body and idle air control. And maybe slap on that old TPS. Then see where you are at.
Another thing to consider. How many miles on the engine? Performing a simple compression test on all cylinders is also never a bad idea as it is a good "snapshot in time" as to the internal condition of your engine. The compression spec. for the 4.0 engine is 120-150 psi, with no more than a 30 psi variation between cylinders. You can rent a compression gauge from many parts stores very inexpensively; call around for availability. A weak cylinder can give you the symptoms you are talking about so don't ignore that possibility, especially for an engine with high mileage. I had one guy bring his XJ to me and he replaced every single engine sensor and most everything else he could get a wrench on but it still ran like crap. A simple compression test confirmed the internals in his engine were on life support. Tail chasing to be sure.
One final thing. Stalling at idle CAN be caused by a marginal battery. And yes, you can have a battery strong enough to start your engine, but marginal enough to cause stalling. Very common actually and I've seen it more times than I can remember. So have you battery "load tested". This service is free at any parts store. When available juice is low, your engine management system is not happy.
So that is exactly how I would approach it if your XJ was in my driveway. Good luck and keep us updated!
-----------------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.
CLEANING THE JEEP 4.0 IDLE AIR CONTROL
Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)
“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner
It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled
Reinstall IAC and check idle quality
Last edited by tjwalker; 11-07-2016 at 07:17 PM.
#7
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Year: 1998 , 1999
Model: Cherokee
Engine: Both 4.0 IL6
One final thing. Stalling at idle CAN be caused by a marginal battery. And yes, you can have a battery strong enough to start your engine, but marginal enough to cause stalling. Very common actually and I've seen it more times than I can remember. So have you battery "load tested". This service is free at any parts store. When available juice is low, your engine management system is not happy.
What is the normal idle RPM supposed to be? Mine periodically wants to dip down to what apears to be 500 or 600 RPM's on the dash tach. When it does this the engine runs rough for a second or two and then bounces back up to about 700-800 RPM's. It was dipping like this before my son left his lights on at school and drained the battery.
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#8
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Join Date: Nov 2010
Location: In the middle of Minnesota!
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Year: 1999
Model: Cherokee
Engine: 4.0
Just went and jumped my son off at school. He has my old '98XJ inline 6. Engine would not keep running. The more I charged the battery, the more it seems to want to run. Hope this is what is wrong with my idle.
What is the normal idle RPM supposed to be? Mine periodically wants to dip down to what apears to be 500 or 600 RPM's on the dash tach. When it does this the engine runs rough for a second or two and then bounces back up to about 700-800 RPM's. It was dipping like this before my son left his lights on at school and drained the battery.
What is the normal idle RPM supposed to be? Mine periodically wants to dip down to what apears to be 500 or 600 RPM's on the dash tach. When it does this the engine runs rough for a second or two and then bounces back up to about 700-800 RPM's. It was dipping like this before my son left his lights on at school and drained the battery.
If your son's battery fails the load test or it it's just plain old as dirt, replace it and see where you are at with your idle speed and stalling problem.