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Old 01-11-2014, 09:54 AM   #1
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95 slow then fast idle?

95 with the 4.0L and 5 speed tranny. When the air temp is cold, 20 degrees, it idles fine until the motor warms up. When it is 40+ out the idle will rev up then drop to almost a stall. The friend of mine that I'm buying the Jeep from was told by a mechanic that it is the fuel pump. Any thoughts?

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Old 01-11-2014, 10:16 AM   #2
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Have you checked for vacuum leaks? I broke a map sensor vacuum line on the brother I laws 4.0 and it did similar things but was corrected once we put a new hose on it

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Old 01-11-2014, 10:28 AM   #3
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might check your idle air control valve they get carbon built up in them some types you can clean others you have to replace
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Old 01-11-2014, 11:26 AM   #4
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Mine did the same way a few weeks ago. Pulled the IAC out. Real bad carbon build up. Replaced it. Its runnin good. Now. The IAC is kinda awkward to get to. Then again doin it in the dark didn't help to much haha
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Old 01-11-2014, 01:05 PM   #5
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Thx for the info so far. I don't have the jeep yet, just looking for a few places to start for the problem. Hope the fix is there and don't have to drop fuel tank.
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Old 02-17-2014, 10:28 PM   #6
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Update. Got the Jeep on Saturday. Spent Sunday cleaning out the inside and then today jumped into the idle problem. When we put the jeep on the trailer to bring it home, the idle was better than previously described. Started with the air filter, was dirty. So I went from there. Cleaned air box to the throttle body. Did the TB Cleaning and TPS. All clean, and running good.
Seems to be running good.

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