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Unread 04-05-2013, 12:19 AM   #1
General Purpose
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1992 YJ Wrangler 
 
Join Date: Aug 2004
Location: Arid part of country
Posts: 85
Low idle 4.0 after rough ride

As as soon as I am on a rough road or any kind of flexing MY RPM drop at idle. It does not stall just sounds like it sucks wind and hovers around 200 RPM. I can hear my throttle body whistle, As soon as I give gas it is OK. As soon as I let off. It is back to low RPM almost stalling. Probably tomorrow it will be OK again at some point in the day. Vacuum?? Fuel pump from all the bouncing around? Why would my TB make noise? Anyone have a similar issue?

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Unread 04-05-2013, 12:21 AM   #2
rawk hard xj
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Loose vacuum line somewhere. Like one on the throttle body.
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Unread 04-05-2013, 12:47 PM   #3
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
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Clean your IAC and throttle body and check your codes on any low idle. A vacuum leak will usually cause a high idle. The TPS or MAP could be suspect, but IAC and codes first.
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Unread 04-07-2013, 11:01 AM   #4
General Purpose
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1992 YJ Wrangler 
 
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Quote:
Originally Posted by Que89YJ View Post
Clean your IAC and throttle body and check your codes on any low idle. A vacuum leak will usually cause a high idle. The TPS or MAP could be suspect, but IAC and codes first.

you called it. I had to replace the IAC, it was pooched. Jeep runs good now. only issue now is I am still throwing codes. Voltage is to to high 15 volts. but alternator reads normal voltage, could be a ground to the ECM?
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Unread 04-07-2013, 11:10 AM   #5
Que89YJ
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1989 YJ Wrangler 
 
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Did you reset the ecu by disconnecting the battery for 10 seconds?
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Unread 04-07-2013, 07:26 PM   #6
General Purpose
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1992 YJ Wrangler 
 
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Yes I did. Just the voltage is registering 15 volts after the ecm.
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Unread 04-07-2013, 09:10 PM   #7
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
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15 volts is not a full field so you aren't going to blow anything up. Normal is 14.5 to 14.9 so you are barely high and I am surprised it throws a fault. I know this is a stretch but are you sure you have the right alternator in there. For an obd 1 your voltage is regulated by the ecu. You need to pull the alternator and get out tested.
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Unread 04-07-2013, 11:04 PM   #8
General Purpose
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1992 YJ Wrangler 
 
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Location: Arid part of country
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Quote:
Originally Posted by Que89YJ View Post
15 volts is not a full field so you aren't going to blow anything up. Normal is 14.5 to 14.9 so you are barely high and I am surprised it throws a fault. I know this is a stretch but are you sure you have the right alternator in there. For an obd 1 your voltage is regulated by the ecu. You need to pull the alternator and get out tested.
Good plan I will do that. thanks for all the help. I will post what I find. I know the alternator has never been changed in the 16 years I owned it. well as far as I remember I never changed it.
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Unread 04-08-2013, 08:15 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
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If you have owned it that long then it is probably the right alternator. Some people swap in an internally regulated alternator and it will function fine but you get the 41 fault and a little worse fuel economy.
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