Loss of power accelerating above 60mph - JeepForum.com
 
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post #1 of 11 Old 01-24-2014, 11:33 AM Thread Starter
tlrthnu
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1999 FSJ Cherokee 
 
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Location: Howell
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Loss of power accelerating above 60mph

I have a 1999 Cherokee, 4.0L, 223,000 miles and I experiencing a problem this morning on my way to work.
After driving for 20-25 minutes at highway speed (70+), several times the engine bogged down (loss of power) while attempting to accelerate, to the point of almost stalling. After easing off the gas for a second or two, I could accelerate again. The problem worsened the faster I went and it only happened above 60 mph.
No dash lights came on and all gauges were normal (they didn't move while engine was bogging), but unfortunately I didn't pay close attention to the tach.
Environmental conditions: outside temp, 2 degrees F; 3/4 tank of gas; clear, level, paved roadway.
Once I exited the expressway, the engine operated normally. No hesitation/bogging/loss of power at all, either while driving or at idle.

I have been searching various forums/sites and have found similar problems, but nothing exactly the same and just as many different possible solutions. I'm hoping someone here has a good idea of which direction I should go to try to diagnose this problem. I am not a mechanic, but I can perform basic and some intermediate diagnostic/shop tasks. However, checking fuel pump, vacuum hoses, pressures, etc. is beyond by ability.

Thanks for your help in advance!

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post #2 of 11 Old 01-24-2014, 11:41 AM
tjwalker
It's the crank sensor!
 
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Actually verifying your fuel pressure is probably easier than you think. A fuel pressure gauge can be rented inexpensively from many parts stores (call around for availability)

Select the correct adapter from the fuel pressure gauge kit and install the gauge on the schrader valve on the fuel rail (looks like the valve stem on a bike tire) That's it!

The fuel pressure spec for your 99 is 49 psi, plus or minus 5 psi. I'd start with this test if your XJ were in my garage. Also review tuneup hardware status whenever symptomatic. That includes plugs, plug wires, distributor cap and rotor......how many miles on these parts?

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #3 of 11 Old 01-24-2014, 10:09 PM
bayhunter
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Loss of power

Was your jeep sputtering and felt like drive train was jerking occasionally?
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post #4 of 11 Old 01-25-2014, 12:21 AM Thread Starter
tlrthnu
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Quote:
Originally Posted by bayhunter View Post
Was your jeep sputtering and felt like drive train was jerking occasionally?
Sputtering, maybe, but I wouldn't describe a jerking motion. It simply slowed down considerably like I was using the engine for braking, but it was more like the engine was stalling. The more I pressed on the gas, the worse it got, until I took my foot off the pedal, when it nearly immediately recovered.
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post #5 of 11 Old 01-25-2014, 07:21 PM
uga84
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2000 XJ Cherokee 
 
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Might sound dumb but if you have floor mats make sure they aren't in the way causing you to not be able to use the pedal correctly. If it's creating a gap between your pedal and floorboard this can make you have the bog down feeling. Or it could be a mechanical issue..
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post #6 of 11 Old 01-26-2014, 07:06 AM
Kalali
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It might be the TPS if the fuel pressure checks out.
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post #7 of 11 Old 01-26-2014, 08:09 AM
ckjeep
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i thought the floor mat thing only happened to me i had a ranger truck that i couldnt get to go over 50 mph once and i realized the floor mat was wedged under the gas pedal
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post #8 of 11 Old 01-30-2014, 12:54 PM Thread Starter
tlrthnu
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Turns out it is the fuel pump. Not a fun (or cheap) repair, but worth it to keep the Tank going for another 10 years.

Last edited by tlrthnu; 01-30-2014 at 03:27 PM.
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post #9 of 11 Old 01-30-2014, 04:38 PM
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by tlrthnu View Post
Turns out it is the fuel pump. Not a fun (or cheap) repair, but worth it to keep the Tank going for another 10 years.
One piece of advice on your new fuel pump assembly. Don't buy an Airtex. They are often offered as a low price point at many parts stores.

My favorite is Bosch. My second favorite is Carter. I won't install nor will I recommend an Airtex to anybody with an XJ.

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #10 of 11 Old 01-30-2014, 06:40 PM
ckjeep
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not a fan of the airtex pumps.unfortunately i rwecently had to put one in a xj because it was the only way to get the entire assembly which i needed. at least if the pump goes bad i will buy a bosch pump and put it on the airtex hangar
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post #11 of 11 Old 01-31-2014, 08:32 AM Thread Starter
tlrthnu
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Location: Howell
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Dealership is installing a Carter at half the price of the Mopar. Doesn't make sense to spend the extra money for a vehicle with over 200,000 miles.
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