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  #1  
Old 10-30-2014, 10:02 PM
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Jeep WJ "surging" idle?

Hello again. So I took advice from an earlier thread about cleaning my iac plunger and did that tonight. After a couple of hours of toying with it I finally got it off and cleaned it. (It was filthy!) well I then went to start the car up and it sputtered then died. I then started it upend had to give it gas to get it going, when I stopped giving throttle it went down to about 500 rpms. It never died again but the idle is awful. Any ideas on what could be causing this? I also heard to change the tps, is there any way to test that before I throw money at it?


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Old 10-31-2014, 08:27 AM
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Re: Jeep WJ "surging" idle?

Did you take care, while cleaning the IAC stepper motor plunjer, to not rotate the plunjer head? The head is hold from rotation by two small plastic pieces, which shear off easily when using a bit too much force while cleaning the plunjer. If its free to rotate, it will not move in and out anymore. Besides this, did you clean the IAC air canal as well?
If that all is ok, then you will need a scanner which can show live data. Android phone with Torque App and a bluetooth dongle will do as well. You can then observe the TPS value in %. Idle is around 11-12%, but the important thing is that it should be a steady value when not touching the throttle. If it jumps a bit, then the TPS needs to be changed.
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Old 10-31-2014, 08:44 PM
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Re: Jeep WJ "surging" idle?

Frango100 I did take care but I can take another look when it's light outside. If the seals are broken is the iac ruined?
Next question is could it also be a camshaft sensor? I was talking with my friend's dad who has had a jeep his whole life and when I showed him what it was ding he said it seemed like the timing was off and that it could be the camshaft.
And one more question is can an obd11 reader check live data?


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Old 10-31-2014, 09:42 PM
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Re: Jeep WJ "surging" idle?

Quote:
Originally Posted by nick_rizer View Post
Frango100 I did take care but I can take another look when it's light outside. If the seals are broken is the iac ruined?
Next question is could it also be a camshaft sensor? I was talking with my friend's dad who has had a jeep his whole life and when I showed him what it was ding he said it seemed like the timing was off and that it could be the camshaft.
And one more question is can an obd11 reader check live data?
The plastic pieces i mentioned are in fact two very small tangs, which just keep the head from rotating. If they are broken, the IAC needs to be changed. You can not see those tangs when the plunjer is in place, but if they are broken, the plunjer can rotate freely.
I presume that the idle was already bad before you attempted to clean the IAC stepper motor?
If the engine runs ok above idle, i won´t expect a cam sensor problem.
Regarding the OBDII reader, it depends which reader you have . The very simple ones only show fault codes, the better ones can show live data as well.
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Old 10-31-2014, 09:59 PM
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Re: Jeep WJ "surging" idle?

Frango100 okay that helps. With the driving part if I am accelerating as soon as I let off the gas my rpms drop very rapidly. I can go from 2000 rpms to 800 instantly. I'm not sure if that matters? Thank you again for all the helpful info!


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Old 11-15-2014, 09:54 PM
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Re: Jeep WJ "surging" idle?

Update:: so I changed the tps and while I did snap two screws in the process... It did the trick!! She fired right up strong as ever and has not had problems since! I do think my next step is to change the iac plunger because I'm still afraid I wasn't careful enough when cleaning it. But anyways thank you all for the help I'm glad I can turn to everyone for help!


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Old 11-16-2014, 04:45 AM
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Re: Jeep WJ "surging" idle?

If it now idles ok, i would not worry about the IAC stepper motor. You can check its function by switching on the AC. Due to the extra drag caused by the compressor, the IAC stepper motor should open up a bit more to compensate. If the idle doesn´t drop while using AC, the IAC is ok.
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