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Unread 12-06-2003, 10:37 AM   #1
Choff
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'93 idle fluctuation and missing

Hi
My '93 4.0L inline 6 recently had been having issues with idling very high-- around 1500-2k. It would obviously bang into reverse, etc. Now, I found a fairly siginificant vacuum leak, on the hose that connects to the plastic "pcv valve lookalike" on the end of the valve cover near the firewall. Having fixed this, it appears that the idling is more normal (though still a little high).
However, now it misses when idling (especially when not in gear), hesitates when taking off, and smells strange.
I thought that perhaps the computer just needed to be reset, so I unhooked the battery for a few hours. No dice. Then, I ran about a half a can of Seafoam in through a vacuum line (as well as putting some in the fuel tank). Also didn't help. I then took some starter fluid and started spraying it on vacuum lines to look for another leak, also nothing. The plugs, wires, cap, and rotor are all new within the past 6 months. The air cleaner is also fine. All the wires are tightly seated, and I pulled the plugs (Bosch Platinum +2) and they all look fine.
I'm not really sure where else to go here.

ANy ideas would be appreciated.
p.s. the fuel pump is also new within about 20k or so

Thanks for reading
Chris

edit: I also pulled the boot off of the throttle body and looked in there. It looks a little dirty. I wonder if this could contribute? I do find it hard to believe that this could be the cause though... but again, I really don't have any other ideas...

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Unread 12-09-2003, 12:21 PM   #2
4XHI
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how is your temp gauge reading??

if its above where it typically runs when idling it may simply be the oxygen sensor. Normally this will drop the rpms though and not raise them.. I'm willing to bet at any rate its a sensor..

rob
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Unread 12-09-2003, 09:10 PM   #3
DrewT
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Quote:
Originally Posted by 4XHI
... I'm willing to bet at any rate its a sensor...
Probally. Do you have a CEL? If so, pull the codes, and post them. Also, check your mileage, it is probally the O2 Sensor...
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Unread 12-14-2003, 08:28 AM   #4
Choff
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HI
thanks for the responses.
I'll probably have to take it in to have it hooked up to a computer to see what's up. I'm not sure if the temp is reading higher than it used to... the jeep came with my new wife, so I'm not sure how it used to be.
I was actually thinking of the O2 sensor. The thing has 116000 on it.
Any idea how much the O2 sensor runs, and is it something I can get to and easily replace myself?

Thanks!
Chris
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Unread 12-23-2003, 01:22 PM   #5
automan25
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Very easy to replace. Took about 15 minutes on my '93 V8. The cost looks to be about $62.49 at NAPA online.

http://www.napaonline.com/cgi-bin/nc...grpid=28591068
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Unread 12-23-2003, 04:09 PM   #6
RockPaws
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It sounds more like the Air idle control valve. They can get sticky and cause this problem. You may be able to remove th evalve and clean with some carb cleaner. If you still have the problem, change the throttle position sensor.
I have seen this problem on a number of customers vehicles, its nomally one or the other. You may take it to Auto Zone and have them test it with their computer.
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Unread 12-28-2003, 11:04 AM   #7
Choff
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Is that the small round valve, near the front of the engine, on the FI rail (not sure of the proper term for that) with a large vacuum line attached to it?
I also noticed that the throttle body has a lot of black deposits around the butterfly.
Thanks
Chris
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Unread 12-30-2003, 07:33 PM   #8
RockPaws
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The round valve on the fwd end of the fuel rail, is the Fuel Pressure regulator. It is controlled by vacume pressure.

I clean my throttle valve valves with fuel injection spray cleaner. With the engine off, I spray around the valve area. Then open it, and finish off the bottom side and bore area.
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Unread 12-30-2003, 07:59 PM   #9
Choff
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I cleaned everything I could clean and plugged up the vacuum leak again. It still misses and hesitates, idle fluctuates, and smells funny... but not as badly as before. I think I will have to have it checked out. The check engine light is not on, but maybe if they poll the computer they can find something (or see something I did not)
It drive me crazy when my vehicles aren't running right!

Thanks
Chris
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Unread 07-22-2004, 06:45 AM   #10
drjake77
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Missing

Choff what did you ever find out what the problem was my 93 is doing the same thing
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Unread 07-22-2004, 03:15 PM   #11
Choff
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Quote:
Originally Posted by drjake77
Choff what did you ever find out what the problem was my 93 is doing the same thing

I replaced the O2 sensor and cleaned the IAC valve. It was all better after that.

HTH
Chris
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Unread 09-09-2004, 09:57 PM   #12
boxoffire
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Rockpaws, you hit the nail on the head in my case. I have a 93 that was idleing high at startup sometimes and wouldn't come back down. Then it would stall out at stop lights sometimes cause idle was too low. Carried to my mechanic and he replaced that valve you mentioned (Air idler control valve) and I spent freakin $260 to have it all fixed. Wonder if I could have just had it cleaned like you suggested, or was he probably being straight up that it needed replacing? It did fix the problem, so far, though he may need to readjust it somewhat cause it seems to idle a bit low and especially when A/c is running. Thanks.
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