Hesitation/bucking on acceleration??
01-27-2010, 11:26 AM
#31
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Year: 1999
Model: Cherokee
Engine: 4.0l I6
Also you need to replace your cat as well. That causes alot of problems with hesitation on accelaration and will affect gas mileage when clogged.
01-27-2010, 02:23 PM
#33
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If there's a bad electrical connection yes....that or you have a clogged pre-filter/fuel filter either one could cause the pump to not feed enough fuel to the engine which causes a lean condition and the bucking/hesitation you're experiencing.
Vacuum lines wouldn't cause that. They'd cause a high idle and other issues, but they won't cause bucking like he's dealing with.
Vacuum lines wouldn't cause that. They'd cause a high idle and other issues, but they won't cause bucking like he's dealing with.
01-28-2010, 11:55 AM
#34
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Year: 1995
Model: Cherokee
Engine: 4.0
thanks for ruling out my vac lines. is there a link that shows how to test each injector? tested the connectors with test light wiring good. code 27 is vague to which injector is bad.
01-28-2010, 10:11 PM
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09-21-2012, 11:32 AM
#37
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Year: 1997
Model: Cherokee
Engine: 4.0L
I'm going to go ahead and revive this thread...
Could it be a bad torque converter by chance? I am currently having the same issuse, and have been for years now. Only in the past 2 weeks has it finally gotten worse. So far I have tried cleaning the neutral safety switch, new mass flow sensor, new fuel pump, new IAC, new TPS, replaced the cat with a straight pipe, and still no helping my problem.
By the way I have a 97 AW4 with 180k.
Thanks alot everyone
Could it be a bad torque converter by chance? I am currently having the same issuse, and have been for years now. Only in the past 2 weeks has it finally gotten worse. So far I have tried cleaning the neutral safety switch, new mass flow sensor, new fuel pump, new IAC, new TPS, replaced the cat with a straight pipe, and still no helping my problem.
By the way I have a 97 AW4 with 180k.
Thanks alot everyone
10-31-2012, 05:30 AM
#38
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Year: 1998
Model: Cherokee
Engine: 4.0L I6
I am having a similar prblem with my 98 xj 4.0 auto. trans
Idles great. When I drive it cold it runs fine. After I drive for 30 to 45 mins I loose power over 2000 rpm. The engine coughs, pops, hesitates, and then regains power for a second then repeats. The problem starts mild then gets worse over 15 to 20 mins. At first I can overcome it by driving it hard on the gas, but once it gets bad the best I can do is control the power loss/surging/popping/hesitation by feathering the gas very lightly.
It will idle fine and drive at light gas pedal pressure/ low rpm fine but it wont hardly accellerate.
Sometimes if I hammer on the gas when its doing it bad the vehicle will respond like Im driving a manual trans and dont know how to drive. (Thats the best way I can describe it) Or it will totally die and backfire.
Gets worse the longer I drive. After I let it sit for 10 mins (not enough to cool the engine) it runs better or fine for about the same amount of time.
Also there is no smell of unburnt fuel.
Even when the problem is happening it idles great. Never had an issue starting the engine. Ive replaced the plugs, wires, cap and rotor.
Idles great. When I drive it cold it runs fine. After I drive for 30 to 45 mins I loose power over 2000 rpm. The engine coughs, pops, hesitates, and then regains power for a second then repeats. The problem starts mild then gets worse over 15 to 20 mins. At first I can overcome it by driving it hard on the gas, but once it gets bad the best I can do is control the power loss/surging/popping/hesitation by feathering the gas very lightly.
It will idle fine and drive at light gas pedal pressure/ low rpm fine but it wont hardly accellerate.
Sometimes if I hammer on the gas when its doing it bad the vehicle will respond like Im driving a manual trans and dont know how to drive. (Thats the best way I can describe it) Or it will totally die and backfire.
Gets worse the longer I drive. After I let it sit for 10 mins (not enough to cool the engine) it runs better or fine for about the same amount of time.
Also there is no smell of unburnt fuel.
Even when the problem is happening it idles great. Never had an issue starting the engine. Ive replaced the plugs, wires, cap and rotor.
11-25-2012, 10:05 PM
#39
My jeep is doing the same thing ... randomly, when accelerting ... I hold the gas steady, but the jeep actually slows down even in RPMs ... then after seems like 2-3-4 seconds, it "lurches" forward and the cycle repeats again.
It feels kind of like when you try to start from a dead-stop - in 3rd gear or something. complete lack of power
If I let off the gas, it "goes away" ... but of course, I'm decelerating which isnt good when trying to drive up a hill.
One thing odd though, if I get it up to 3k RPMs -- it "jumps" alive and cruises along with no hesitation problems.
And it seems to be much worse, if I don't let it warm up before driving.
I'm thinking maybe I have vacuum leak or possibly O2 sensor issue?
Some history on what I've tried:
* just replaces all (6) fuel injectors with new (4) hole kinds (thought it might help, but problem more frequent now)
* replaced coil with aftermarket one last fall, forget the name but it allowed the plugs to use a wider gap ... and added some power. (but didnt cure the issue)
* engine was complete rebuilt 2006 - still no oil leaks, etc. But so far I've replaced the following; TPS, CPS (crank sensor), (4) Fuel Pumps, (1) Water Pump plus the usual tune-up stuff ... plugs, plug wires (high temp kind, came with new ignition coil), filters, etc.
If not for this hesitation, I'd be driving this Jeep every day ... I love it.
But it hesitated and even stalled out while trying to 4x4 up a steep hill the other day ... and did this hesitation thing for about 10m today while driving into work
Gets bad enough my wife is now afraid to drive the Jeep ...
Please let me know if any suggestions / ideas on how to troubleshoot this issue are appreciated!!
It feels kind of like when you try to start from a dead-stop - in 3rd gear or something. complete lack of power
If I let off the gas, it "goes away" ... but of course, I'm decelerating which isnt good when trying to drive up a hill.
One thing odd though, if I get it up to 3k RPMs -- it "jumps" alive and cruises along with no hesitation problems.
And it seems to be much worse, if I don't let it warm up before driving.
I'm thinking maybe I have vacuum leak or possibly O2 sensor issue?
Some history on what I've tried:
* just replaces all (6) fuel injectors with new (4) hole kinds (thought it might help, but problem more frequent now)
* replaced coil with aftermarket one last fall, forget the name but it allowed the plugs to use a wider gap ... and added some power. (but didnt cure the issue)
* engine was complete rebuilt 2006 - still no oil leaks, etc. But so far I've replaced the following; TPS, CPS (crank sensor), (4) Fuel Pumps, (1) Water Pump plus the usual tune-up stuff ... plugs, plug wires (high temp kind, came with new ignition coil), filters, etc.
If not for this hesitation, I'd be driving this Jeep every day ... I love it.
But it hesitated and even stalled out while trying to 4x4 up a steep hill the other day ... and did this hesitation thing for about 10m today while driving into work
Gets bad enough my wife is now afraid to drive the Jeep ...
Please let me know if any suggestions / ideas on how to troubleshoot this issue are appreciated!!
I've recently replaced the coils, spark plugs and TPS.
Any updates you have would be greatly appreciated!
11-27-2012, 07:22 PM
#40
***UPDATE***
I finally had to bite the bullet and take it into the repair shop since it's my primary vehicle and I can't miss work to tinker with it (grrr). The mechanic charged me an arm and a leg to tell you all what you should already know, which is:
USE FACTORY REPLACEMENT THROTTLE POSITION SENSORS.
Again, in case you didn't catch that (like I didn't the first time):
USE FACTORY REPLACEMENT THROTTLE POSITION SENSORS.
I replaced the TPS with a third party piece for ~20 bucks. Ultimately, the third party TPS failed, and led me on a wild goose chase trying to locate the source of the problem.
So, what could have been an $80.00 fix if I'd purchased the correct part became a $280 job for the mechanic pus $20 on the faulty part.
Lesson learned!
I finally had to bite the bullet and take it into the repair shop since it's my primary vehicle and I can't miss work to tinker with it (grrr). The mechanic charged me an arm and a leg to tell you all what you should already know, which is:
USE FACTORY REPLACEMENT THROTTLE POSITION SENSORS.
Again, in case you didn't catch that (like I didn't the first time):
USE FACTORY REPLACEMENT THROTTLE POSITION SENSORS.
I replaced the TPS with a third party piece for ~20 bucks. Ultimately, the third party TPS failed, and led me on a wild goose chase trying to locate the source of the problem.
So, what could have been an $80.00 fix if I'd purchased the correct part became a $280 job for the mechanic pus $20 on the faulty part.
Lesson learned!
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12-03-2012, 01:55 AM
#41
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Year: 1998
Model: Cherokee
Engine: 4.0L I6
Problem Solved
I am having a similar prblem with my 98 xj 4.0 auto. trans
Idles great. When I drive it cold it runs fine. After I drive for 30 to 45 mins I loose power over 2000 rpm. The engine coughs, pops, hesitates, and then regains power for a second then repeats. The problem starts mild then gets worse over 15 to 20 mins. At first I can overcome it by driving it hard on the gas, but once it gets bad the best I can do is control the power loss/surging/popping/hesitation by feathering the gas very lightly.
It will idle fine and drive at light gas pedal pressure/ low rpm fine but it wont hardly accellerate.
Sometimes if I hammer on the gas when its doing it bad the vehicle will respond like Im driving a manual trans and dont know how to drive. (Thats the best way I can describe it) Or it will totally die and backfire.
Gets worse the longer I drive. After I let it sit for 10 mins (not enough to cool the engine) it runs better or fine for about the same amount of time.
Also there is no smell of unburnt fuel.
Even when the problem is happening it idles great. Never had an issue starting the engine. Ive replaced the plugs, wires, cap and rotor.
Idles great. When I drive it cold it runs fine. After I drive for 30 to 45 mins I loose power over 2000 rpm. The engine coughs, pops, hesitates, and then regains power for a second then repeats. The problem starts mild then gets worse over 15 to 20 mins. At first I can overcome it by driving it hard on the gas, but once it gets bad the best I can do is control the power loss/surging/popping/hesitation by feathering the gas very lightly.
It will idle fine and drive at light gas pedal pressure/ low rpm fine but it wont hardly accellerate.
Sometimes if I hammer on the gas when its doing it bad the vehicle will respond like Im driving a manual trans and dont know how to drive. (Thats the best way I can describe it) Or it will totally die and backfire.
Gets worse the longer I drive. After I let it sit for 10 mins (not enough to cool the engine) it runs better or fine for about the same amount of time.
Also there is no smell of unburnt fuel.
Even when the problem is happening it idles great. Never had an issue starting the engine. Ive replaced the plugs, wires, cap and rotor.
For my XJ it was a O2 sensor. Easy way to test, unplug the sensors and drive. If it doesnt make it any better then you know its something else.
01-19-2013, 09:51 PM
#42
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Year: 1989
Model: Cherokee
Engine: I6 4.0
I did unplug it and it only made it worse. I've replaced the iac, tps, plugs, wires, cap, rotor, ignition coil, fuel filter and the coolant temp sensor like someone said on another thread. Anyone have any other ideas? I need my jeep back!
Last edited by Ryno 82; 01-19-2013 at 09:53 PM.
01-26-2017, 08:18 AM
#44
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Hi! I have been battling with my Jeep for a few weeks with very similar issue. Although mine has a wiring issue (I think) you may want to test your map sensor. Power from PCM to the map is easy to test. The Map Sensor itself is a bit trickier to test if you don't have a vacuum, but you can suck with your mouth if you have enough hands and gadgets to hold things.
Map Symptoms- Vehicles with a bad manifold absolute pressure (MAP) sensor typically run rough while accelerating, decelerating or idling. Other common symptoms include increased fuel consumption and sudden jerks or hesitation while accelerating. Drivers may detect a strong smell of gas after the engine has warmed up.
FYI, about 40 or more vehicles use the same one. I took one off my full size truck and swapped them rather than buy yet another part. Good luck.
