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Bogging on highway when accelerator floored

Old 05-07-2019, 06:54 PM
  #1  
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Cool Bogging on highway when accelerator floored

New to this forum. I hope help can be found. Forgive if this has been asked before, I did a search and found some threads which were close but still did not relay an identical issue.

1996 Cherokee Country, 4.0 HO, automatic transmission. When driving around town, all runs fine. When getting on the highway acceleration must me slow. when I hit a hill or attempt to pass and the accelerator is floored, transmission downshifts like it should and the RPMs will jump up to around 3000, and then the engine starts to bog down. It struggles and loses speed and power until I release the accelerator and let the RPM drop back down and the transmission shifts back up. If I am easy and careful on the gas I can coax it up to speed (65 - 73 MPH). This only occurs when the throttle really opens up and the transmission downshifts as if to accelerate. Travelling on flats and/or down hill I can get it up above 80 with very little problem as long as I don't floor it.

There is no check engine light and the problem cannot be duplicated in a garage or when driving around in normal in town traffic.

I didn't have this issue in the winter when it was cold, but the roads were snowy and icy, so flooring the accelerator wasn't a good idea.
Thank you in advance.
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Old 05-07-2019, 07:16 PM
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Originally Posted by Bradley Miller View Post
New to this forum. I hope help can be found. Forgive if this has been asked before, I did a search and found some threads which were close but still did not relay an identical issue.

1996 Cherokee Country, 4.0 HO, automatic transmission. When driving around town, all runs fine. When getting on the highway acceleration must me slow. when I hit a hill or attempt to pass and the accelerator is floored, transmission downshifts like it should and the RPMs will jump up to around 3000, and then the engine starts to bog down. It struggles and loses speed and power until I release the accelerator and let the RPM drop back down and the transmission shifts back up. If I am easy and careful on the gas I can coax it up to speed (65 - 73 MPH). This only occurs when the throttle really opens up and the transmission downshifts as if to accelerate. Travelling on flats and/or down hill I can get it up above 80 with very little problem as long as I don't floor it.

There is no check engine light and the problem cannot be duplicated in a garage or when driving around in normal in town traffic.

I didn't have this issue in the winter when it was cold, but the roads were snowy and icy, so flooring the accelerator wasn't a good idea.
Thank you in advance.
This is a long stretch but had a very similar problme on my 89 jeep for a while. Didn't really notice it except when trying to get up to speed quickly or going up hill. Similar to what you described.

Went to do a valve cover replacement and noticed I had a push rod just sitting not in place. Pulled it out and it was bent. Also had a lifter out because when the bent rod came up so far it let it slide out. So I had to take the head off and replace the rod and lifter, and went ahead and did the head gasket of course.



I had been driving on 5 cyl for months but the jeep was new to me so I just chalked it up to being a slow jeep hahaha.

Last edited by Chick-N-Picker; 05-07-2019 at 07:20 PM.
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Old 05-07-2019, 08:16 PM
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gat
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What is your fuel pressure? You can "rent" a free gauge from O'Reilly's et cetera. Use that to measure the pressure with the ignition off, ignition to run after 2 seconds, while starting, while idling, and about 40 seconds after killing the engine. Sometimes the fuel pressure at a hill or near top speed is a load that will change the values only when under those loads.
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Old 05-07-2019, 09:38 PM
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Originally Posted by Bradley Miller View Post
New to this forum. I hope help can be found. Forgive if this has been asked before, I did a search and found some threads which were close but still did not relay an identical issue.

1996 Cherokee Country, 4.0 HO, automatic transmission. When driving around town, all runs fine. When getting on the highway acceleration must me slow. when I hit a hill or attempt to pass and the accelerator is floored, transmission downshifts like it should and the RPMs will jump up to around 3000, and then the engine starts to bog down. It struggles and loses speed and power until I release the accelerator and let the RPM drop back down and the transmission shifts back up. If I am easy and careful on the gas I can coax it up to speed (65 - 73 MPH). This only occurs when the throttle really opens up and the transmission downshifts as if to accelerate. Travelling on flats and/or down hill I can get it up above 80 with very little problem as long as I don't floor it.

There is no check engine light and the problem cannot be duplicated in a garage or when driving around in normal in town traffic.

I didn't have this issue in the winter when it was cold, but the roads were snowy and icy, so flooring the accelerator wasn't a good idea.
Thank you in advance.
You should get an OBD2 scanner (I prefer the BAFX brand on amazon for about $25) so that you can see what your fuel trims are doing when this is happening.
Alternatively, you could rig up a fuel pressure gauge so that you can see the dial while you are driving, some pull this off by getting a pressure gauge with enough tubing that the dial can be hung just outside the hood when closed.

It sounds like your fuel pressure might not be holding steady when the demand for fuel is very high. Not an outright failure, just the pump being unable to produce the pressure required under peak demand.
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Old 05-08-2019, 09:42 AM
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Thank you to those who replied. Let me add to this for better clarification. I can get the engine to duplicate efforts in town driving when I floor from a stop. Initially the launch is good but once the engine climbs above 3200 ish RPMS the bogging starts and it wont shift to the next gear. The bogging feeling doesn't seem like it is starving for fuel, rather it feels like it is getting too much fuel, and the transmission tries to hold whatever gear it is in at the time.
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Old 05-08-2019, 10:32 AM
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gat
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I don't think that it is more likely to be shorter on air than higher on air. A big is usually on the intake side of things which is the fuel-to-air ratio. Since the injectors are pulsed, then an issue with inadequate fuel would be the pressure. An issue with inadequate air would be a very clogged filter or a pinched boot. It is worth looking into both sides of the intake.

It could be an exhaust issue in that the combustion gases are not leaving the vehicle fast enough, but I would guess that a clogged catalytic converter would bog the engine across all ranges of load.

High load bogging seems to be a constant fuel pump from the threads that I have read on this forum. A clogged fuel filter would inhibit flow as well, though.
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Old 05-08-2019, 06:10 PM
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Originally Posted by gat View Post
I don't think that it is more likely to be shorter on air than higher on air. A big is usually on the intake side of things which is the fuel-to-air ratio. Since the injectors are pulsed, then an issue with inadequate fuel would be the pressure. An issue with inadequate air would be a very clogged filter or a pinched boot. It is worth looking into both sides of the intake.

It could be an exhaust issue in that the combustion gases are not leaving the vehicle fast enough, but I would guess that a clogged catalytic converter would bog the engine across all ranges of load.

High load bogging seems to be a constant fuel pump from the threads that I have read on this forum. A clogged fuel filter would inhibit flow as well, though.
Thank you. You gave me something else to look for. This Jeep was my daughters, short story of it, she was murdered in 2014. The Jeep then passed to her brother, who drove it about a year and a half before he was involved in a collision that damaged front passenger corner, fender, radiator and hood. It sat parked and covered from Dec 2015 till October 2018. It was started about two to three times per year during that time, but with a damaged radiator and no coolant, it couldn't be run very long. I got another Jeep for parts and rebuilt it in October 2018. I just filled the tank and started driving it. I never thought to change out the fuel and/or putting a new fuel filter on it.
As well, reading this forum, I will be looking at the possibility of a clogged Catalytic converter, because it rattles loudly when it is cold, indicating the internal material is loose and rattling.
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