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Unread 03-17-2010, 06:43 PM   #1
spgeid
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1999 WJ 
 
Join Date: Mar 2010
Location: Kittanning, PA
Posts: 7
1999 WJ Overcharge? Run poorly questions

So I bought this WJ. Maybe a big mistake. But...

With the alternator unplugged it runs not too bad. If I plug it in the engine dies down to nearly a stall. Checked the voltage at the battery it is charging at 16 to 17 volts.

Is this enough load to draw the engine to a stall? Or is there another underlying problem? Could the coil pack be overdrawing?

I just change the twin california cataylitics because they back was was plugged. I think it was really red hot from the looks of it.

Anyone have any suggestions besides sell quick?

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Unread 04-24-2010, 02:40 PM   #2
TK32
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Join Date: Apr 2010
Location: Ma.
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Same problem

To bad no one has replied yet mine does the same thing and the gauges start acting up! If you have solved problem please post what you found,thanks tk32

Last edited by TK32; 04-24-2010 at 02:42 PM.. Reason: more info
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Unread 04-24-2010, 03:49 PM   #3
euphoria
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1999 WJ 
 
Join Date: Jul 2009
Location: north carolina
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check the battery terminals, wj's do very crazy things when the terminals have any corrosion of any kind on them
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Unread 04-24-2010, 08:51 PM   #4
TJSWJ
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2001 WJ 
 
Join Date: Mar 2010
Location: Olmsted Falls, ohio
Posts: 2,274
The voltage regulator in the alternator is most likely bad. The jeep is designed to run at 14.6v when charging. If its charging 16+ volts then its throwing the computer and all the sensors off
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Unread 04-25-2010, 07:54 AM   #5
TK32
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Changed voltage regulator still over charged,replaced alternator still same thing. when voltage regulator wire is unplugged vehicles runs almost perfect, plug it back in and it starts to buck skip it's strange. Battery terminals are nice and clean tk32
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Unread 04-25-2010, 08:11 PM   #6
spgeid
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1999 WJ 
 
Join Date: Mar 2010
Location: Kittanning, PA
Posts: 7
Here is what I learned.

The charging system on the 99 WJ is completely controlled by the PCM. If you have an overcharge the PCM needs replaced. My gauge was acting goofy on the dash also. Change out the PCM and fix the bucking engine problem, gauge problem and charges at the right voltage now. I found the best buy on E-bay from a PCM exchange company in Florida. $150 shipping included. They were reasonably fast also. About 4 days to get mine. The alternator itself on the 99 WJ (mine was a bosch) does not have any regulator built into the unit.
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Unread 05-02-2010, 11:16 AM   #7
TK32
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Where is pcm located on this vehicle?
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Unread 05-02-2010, 12:55 PM   #8
spgeid
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1999 WJ 
 
Join Date: Mar 2010
Location: Kittanning, PA
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PCM location

On the firewall on the passenger's side.
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Unread 05-04-2010, 09:24 AM   #9
TK32
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thank you I'm going to replace it. When I got this Jeep I was told voltage regulator and then alternator were replaced thank's for the info about how this charging system works, they should have left the charging duties out of the computer it would have made things easier! thanks again tk32
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Unread 06-15-2013, 09:47 PM   #10
Chevymanjohniii
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I'm having the same problem with a 99 WJ I just bought for my wife. It toasted the battery an a hurry but then again that's what I'd expect. I came to the conclusion that the ECU was the overcharging culprit, but I wasn't sure if it would cause the volt gauge to not work. It drops when the key is off and comes up a little when the key is on but that's it. Will replacing the ECU fix that too does anyone know? I haven't been able to find a good pin out diagram for the ECU so I can check out some wires. Thanks in advance for any help.
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