1990 yj 2.5l high idle. - JeepForum.com
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Unread 08-06-2013, 06:28 AM   #1
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1990 yj 2.5l high idle.

My 90 yj idles between 1000 and 1500 rpm I don't think it should be that high... Anyone have any ideas as to why it started idlein do high

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Unread 08-06-2013, 10:10 AM   #2
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1991 YJ Wrangler 
Join Date: Jul 2012
Location: Walland/Knoxville, Tennessee
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I am also interested to know how the idle is controlled on these. mine began idling high after replacing map and tps.
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Unread 08-06-2013, 11:42 AM   #3
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1989 YJ Wrangler 
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Location: Pittsburgh, PA
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Check ALL the rubber hoses including the 4 short ones on the passenger side of the throttle body to make sure you don't have a vac leak.

The idle (fuel/air delivery) is controlled by a couple different sensors but mains ones are MAT TPS CTS WOT MAP and idle air motor. All these have potential to affect the idle so break out your multimeter and start testing them. If you don't know the testing process let me know and I can post them.

Mechanically, it could be too much fuel pressure which should be around 14.5 psi. Test port is an Allen plug on the driver side of the TB by the vacuum booster check that with a standard pressure gauge and a Schrader valve
89 YJ S, 2.5L/AX-5/NP231
99 WJ Limited, 4.0L/42RE/NP247
93 YJ, 4.0L HO/32RH/NP231 - Sold
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Unread 08-06-2013, 02:20 PM   #4
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1990 YJ Wrangler 
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Location: Elizabeth Lake, CA
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Also check the PVC valve. If its stuck open, it would create a vacuum leak and cause it to idle high.
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Unread 08-08-2013, 09:19 PM   #5
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Thanks for the info! Will let you know what I find out.
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