1998 Jeep Cherokee misses about half way up to normal temp

Tiny
TGFH
  • MEMBER
  • 1998 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 117,000 MILES
My Cherokee misses and back fires during warm up. It starts great and runs fine when cold. Then at about 140 degrees to maybe 180 it runs rough. And under power it back fires. Then once it's up to the normal 200 it runs great. I just finished replacing all the front parts (deer) - pass. Fender, nose piece and grills, bumper, both radiators, their mounts and had to straighten the inner headlight surround. I replaced the vacuum canister and the line to the cruise control servo. The heater works and so does the cruise. Am I missing some vacuum lines in that front passenger side?
Thanks
Friday, February 5th, 2010 AT 8:17 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Does the check engine light come on when this happens? As far as vacuum hoses, it doesn't sound like you missed any. I assume it didn't do this until after hitting the deer. To me, it sounds like a bad temp sensor. Let me know about the light.

Joe
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Monday, February 8th, 2010 AT 9:52 PM
Tiny
TGFH
  • MEMBER
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No engine lights and the last time I drove it - it didn't happen - frustrating!
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Tuesday, February 9th, 2010 AT 9:54 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
That is frustrating. My first guess is the temp sensor. If it isn't working correctly, it won't send the correct signal to the computer. As a result, it can cause the engine to run too rich or lean at certain temps.

If it happens again, let me know.

Joe
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Tuesday, February 9th, 2010 AT 7:49 PM

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