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Old 05-25-2013, 04:42 PM   #1
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changed alternator now high idle

Hello everyone,
Today I came out of work and my 95 yj was dead. I push started and she fired right up. While drive my gauges died. When I got home I disconnected the positive side of the battery and the engine died. So I ran down to oriley's and picked up a new 90amp alternator. After installing it, push started it again and fired up but it was idling at almost 4,000rpm then revved up and pegged the limiter. Does anyone have any idea where to start looking? It looked like the alternator only connected one way. The Jeep is a 95 yj 2.5l five speed if that helps.

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Old 05-25-2013, 05:14 PM   #2
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did you have your old alternator checked before you got a new one??

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Old 05-25-2013, 05:38 PM   #3
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Don't see how the alernator would affect the idle unless you smoked the pcm or disconnected or shorted a wire. When changing the alternator.
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Old 05-25-2013, 09:52 PM   #4
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They checked the old one and said it was fried. I have been going through the harness and haven't seen any disconnected wires or signs of a short. Is there anyway to check the pcm?
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Old 05-25-2013, 11:52 PM   #5
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Have you checked the battery voltage while the engine is running and charging it? If the regulator is not right maybe too high a voltage could explain the high idle?
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Old 05-26-2013, 01:08 AM   #6
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I haven't checked the voltage while it is running because about 45 seconds after it starts the engine RPMs shoot up to 6,500 rpm. I will try to check it tomorrow and see if I can get any readings before it's wrapped out.
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Old 05-26-2013, 02:29 AM   #7
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Possibly ck to see if you have a loose ground somewhere. Mine had done the same thing when I changed it, just not as bad. I had two loose grounds. Also ck to see if ur battery ground is good.
You may have wiggled somthn loose somewhere when swappn out you alt.
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Old 05-28-2013, 11:13 PM   #8
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Hey guys. I finally finished looking through all of the ground connections I could find. Nothing significant. So we jumped the battery and it started right up with no problems. Took it for a 30 min drive. Everything is good. Thanks guys I really appreciate all of the advice.
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Old 05-29-2013, 01:38 AM   #9
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Did you knock off a Vacuum line replacing your Alternator? the big one to the Brake Booster will do this....
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Old 05-30-2013, 12:06 AM   #10
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Nope I had that happen on the trail about a month ago that was the first thing I checked this time. I will just keep an eye out for it seems like a ghost in my wiring some where.

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