1999 violent bucking and loss of power

Tiny
TOMTOM21013
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 85,000 MILES
When going up steep hill @ 45mph and 3000rpm. The jeep will buck and seem to lose power. Not sure if it is trans. Or engine.
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Sunday, August 17th, 2008 AT 7:30 PM

5 Replies

Tiny
SERVICE WRITER
  • EXPERT
Check the fuel pressure when the problem is happening by running a gauge out to the windsheild so it can be monitored. I am suspcting a weak fuel pump.
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Sunday, August 17th, 2008 AT 8:25 PM
Tiny
TOMTOM21013
  • MEMBER
Fuel pressure is 47-48psi and steady when problem happens
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Saturday, August 23rd, 2008 AT 11:29 AM
Tiny
SERVICE WRITER
  • EXPERT
Okay fuel pump is fine based on The specs (44-54psi) for this one: 1999 Grand Cherokee Larado 4.0.

IS this what you have?

Does this happen when the engiine is cold or not?
Check for codes in the pcm, if possible check the O2 Sensor wave pattern.

Have any carbon removal procedures been done?

Check coil pack resistance.
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Sunday, August 24th, 2008 AT 9:40 AM
Tiny
TOMTOM21013
  • MEMBER
I have been driving the Jeep a little this week. It is a 99 Cherokee Sport with 4.0L /auto trans. I find it will miss or slip at any rpm but must be under a load. At first it seemed to only act up in overdrive but have found it to show the same problem in drive(3rd). Pulled two plugs (2, 5) both looked clean and in good shape. Plugs, wires and cap were replaced 3.5 years ago (60,000), when the crankshaft sensor went up. Cap showed some pittng. Does not seem to happen with the engine cold but will after 15min. Have not done anything else to the motor (cyl. Or inj). Jeep has 90,000 miles now. What should the coil res. Be cold and hot?
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Sunday, August 24th, 2008 AT 7:56 PM
Tiny
SERVICE WRITER
  • EXPERT
I guess it's a good thing it isn't the grand Cherokee.


http://www.2carpros.com/forum/automotive_pictures/30961_jee_2.jpg



I don't have a hot or a cold spec other than this.

I found this on mitchell, and wanted to throw ot out there.:
Cust comlaint:
Rough idle in high ambient after hot soak. Clears in 30-60 SEC
Cause:
Exhaust heat causing fuel in #3 and #4 injector to vaporize.
Repair:
Install heat sleeve, PN56028371AA, on injectors

Long shot, but.....
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Sunday, August 24th, 2008 AT 8:55 PM

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