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Unread 10-15-2013, 10:17 PM   #1
gwak
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1994 ZJ 
 
Join Date: Oct 2011
Location: Somewhere in, USA
Posts: 33
Jeep won't idle without throttle



I replaced the water pump on my jeep today finally. Battery was unhooked for a little over week, no problems with it before. I had removed the AC compressor, alternator and power steering pump, air box, and tube going to the intake. I have checked all cables and connections over and over again.

When I started it up it idled extremely rough for about a minute, then steadied out to what I would consider a normal idle and had no problem idling. When I would give it gas then let off it would die unless I hit the throttle again. I can't find anything that I messed up anywhere.

I did notice when I went to hook the negative cable back in that the red part I marked had crumbled and is basically just hanging there not making much for contact and the positive cable isn't much better. Is this just a issues with those connectors? I have to have this running in the morning so I need a quick emergency fix.

Edit: If I slowly let off the gas it will go back to a very low idle.

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Unread 10-15-2013, 10:55 PM   #2
newfieZJ
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did you try to retrieve a code from the PCM ? Give it s shot and let us know what you come up with other than codes 12&55
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Unread 10-15-2013, 11:03 PM   #3
gwak
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Just checked and it is throwing 32. It has been throwing that for about 2 years. I just saw no point in spending $200 on a valve that does nothing. I have never had issues with it not working. Unless 32 is also related to bad wiring.

Edit: I also never drove around. Google searching said that the ECM needs to relearn how to idle. Could this be it?
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Unread 10-15-2013, 11:03 PM   #4
newfieZJ
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Ever clean the IAC
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Unread 10-15-2013, 11:08 PM   #5
gwak
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Nope. I have just heard of it though. Seems odd that it would be an issue all of a sudden. :/

Edit, Just found a thread with pictures.

http://www.jeepforum.com/forum/f13/h...-valve-756934/

Do I just remove the four bolts to take the TB out? In all honesty half of this stuff is over my head. I struggled just to replace the water pump. I don't want to be screwing anything up. I had the hose off of there for a week so maybe a bunch of dirt dust and crap made it in and clogged it?
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Unread 10-15-2013, 11:19 PM   #6
newfieZJ
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Quote:
Originally Posted by gwak View Post
Nope. I have just heard of it though. Seems odd that it would be an issue all of a sudden. :/
http://www.jeepforum.com/forum/f13/h...ighlight=clean

Most things happen just like that . When getting my jeep going last month , it started fine but wouldn't idle . I looked at the IAC but it was clean . Broke the TPS doing it so it got replaced , tried to restart it and the battery died . Got it going with a new battery and all was well . Went for a test drive of only 2 miles , parked it in front of the garage , it died . CPS failed .
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Unread 10-15-2013, 11:31 PM   #7
newfieZJ
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Disconnect the battery , unplug the sensor , 2 torx (T-20) screws and remove it . Spray the mushroom shaped plunger with cleaner and use an old toothbrush to clean it down . Rinse it off with cleaner and let it sit to dry . Don't twist or push in on the plunger at any time . Spray some cleaner in the hole the sensor came from , try to get the tooth brush in there , use some q-tips if you have to and wipe it out after with a cloth or paper towel .

Spray some cleaner on the throttle plates , open them fully , scrub with the brush anywhere that looks dirty , spray again with the cleaner .

Re-install sensor , reconnect battery , fire it up . Idle is typically rough at first and gets better when it warms up as the PCM is relearning .
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Unread 10-15-2013, 11:36 PM   #8
kodybonham
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I had a similar issue with my zj. It had sat four about four years when i got it (So the battery was no good, also not hooked up anyway), after replacing the plugs, wires, filters, etc.. and replaced the entirely dead battery the jeep was able to start. But like yours the idle was terrible, it was very erratic especially when put into gear. RPM's would drop low and sputter and it would either die or the RPM's would shoot back up to normal. I checked various sensors, TPS and etc. with none of them showing any problems. I learned about the IAC valve issue through the forum. I checked mine and it was pretty bad so i went ahead and replaced it, idle improved but i was still experiencing the idle problem. I could drive it but when decelerating the RPM's would again drop and the jeep died about every other time. But what you mentioned about it relearning how to idle, I believe is correct, the more i started it, put a load on it and drove it, the better the issue got until i didn't notice it at all.
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Unread 10-16-2013, 12:23 AM   #9
rlcii77
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All of my ZJs would have a rough time idling for a while after disconnecting the battery. I'd have to slowly take my foot off the accelerator, or else they'd die... After driving them, the ZJs seem to "re-learn" everything and idle, operate smoother and more efficiently overall... I'd replace that terminal too...
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Unread 10-16-2013, 03:40 PM   #10
gwak
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Got it fixed this morning. Turns out my meeting was canceled at the last minute so I didn't have to limp it. I took some metal shears and cut the negative terminal off since it was in such bad shape. Got a new one from NAPA with the clamp on it. Works good and looks good. I just had to cut about 3/4 inch of insulation off of the wires. Red wires don't have enough slack to do that so I have a headache on my hands when it comes time to do those.

I took the IAC off and it was worse than the picture of the one in the thread I linked earlier. Cleaned it up and cleaned the port for it. I didn't think I would have time to clean the TB but it is absolutely filthy. I'll go back for it at a later date.

Started and idled just fine in 25F. Sure enough it was dying when I would gas it then let off. I decided to just drive around for about 15 minutes. It has been running fine now.
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Unread 10-16-2013, 09:05 PM   #11
kodybonham
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good to hear
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