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1995 Jeep Grand Cherokee

Tiny
GLDAVID
  • MEMBER
  • 1995 JEEP GRAND CHEROKEE
  • V8
  • 4WD
  • AUTOMATIC
  • 179,000 MILES
This has been happening since I got this vehicle. At highway speeds there is misfire under light acceleration. Only happens under a light load. I changed all my tune up parts (cap, rotor, plugs, wires) with no change. No codes, and all the sensors seem to be within spec.
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Saturday, October 16th, 2010 AT 8:22 AM

4 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Engine running rough or misfiring can be cause by the following:

1. Defective spark plug
2. Inadequate spark/coil, defective spark plug wire.
3. Lack of compression
4. False air leakage.
5. Faulty fuel injectors.
6. Insufficient fuel pressure.
7. Contaminated fuel.
8. EGR valve that is leaking.
9. Oxygen sensors.
10. Throttle position sensor.
11. Idle air control valve.
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Saturday, October 16th, 2010 AT 9:21 PM
Tiny
GLDAVID
  • MEMBER
  • 6 POSTS
The problem is that it is only under a very light load. Otherwise it runs fine. If I disconnect the Manifold absolute pressure sensor it doesn't do it. But if I monitor the MAP sensor while it is happening it is within spec. O2 sensors are switching regularly. I just don't know where to go. I have suspected fuel injectors in the past, but the fact that it goes away in fault mode lowers my suspicion.
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Saturday, October 16th, 2010 AT 9:40 PM
Tiny
GLDAVID
  • MEMBER
  • 6 POSTS
The TPS is also within spec.
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Saturday, October 16th, 2010 AT 9:42 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Double check the MAP sensor and wiring and also check the EGR valve.
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Saturday, October 16th, 2010 AT 9:55 PM

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