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Old 10-12-2005, 07:23 PM   #1
blu
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High Idle

Hi guys,
I'm a newbie from Sydney Australia. My 97TJ 4.0L is idling to high, just under 1000 revs. When I put the clutch in, the revs take much longer to drop, and then they hang around the 1000 mark rather than drop to 800. Sometimes the revs are pulsating slightly, like a carby CJ.
What could be the problem? The ignition diagnostic reveals nothing, and she is always in top condition, clean engine, serviced regularly. She has done 85,000 kms.
Thanks in advance for any solutions...
Rob

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Old 10-12-2005, 09:59 PM   #2
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Rob, I would start by checking the TPS...my .02...Bob

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Old 10-12-2005, 10:12 PM   #3
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Rob, I would start by checking the TPS...my .02...Bob
Thanks Buster, but how do I check the TPS? I have changed it already, about 2 years ago. Here in OZ the dealership charges so much for parts and labour, the bill is around $500.
I would prefer to check it myself. Any clues??
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Old 10-13-2005, 04:11 PM   #4
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500!!! HOLY CRAP! i changed mine for $38(price for TPS at auto zone). i'd start at the throttle body, make sure it's good and clean and working properly. you might change all the sensors attached to it(TPS, AIS motor, MAP). if nothing there changes, you can always take those back and flashing the ECU might not be a bad idea either. click here for that
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Old 10-13-2005, 07:28 PM   #5
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I`d check the IAC- which on yours is probably the AIS-- at any rate, Idle Air Control- little barrel lookin thing next to the TPS--- shoot, I dont even know where it is on yours.

anyway- the IAC controls Idle- it lets a metered ammount of air into the throttlebody to mix with the static air and fuel-- too much causes the engine to rev up...and its hard to get too little because of the design.

the main problem we have is crap gets on the end (pintle) of the IAC- makeing it not close or to where it needs to be specificly...pull the IAC out, wipe off the pintle, look inside the bore (where you took it out of the TB) and clean the rim where the pintle sits-- ANY carbon, crap, gunk, whatever-that interferes with the IAC will cause fluttering idle/high idle.

The TPS is always the second culprit- especially if the vehicle is an automatic-but rule out the IAC first.
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Old 10-13-2005, 09:00 PM   #6
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Thanks ED,
I have tried to unplug the IAC but it is difficult. It feels stuck. I am able to unclick it but I can't remove it. Any advice? I am scared I will break something. The prices here are so expensive compared to the U.S. And there is no where here where we can take our Jeep to get a diagnostic OBDII. We have to go to the dealership and they charge us $95 just for a diagnostic...
Anyway, any tips on how to take apart the IAC?
Thanks,
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Old 10-14-2005, 06:16 AM   #7
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Originally Posted by blu
Thanks ED,
I have tried to unplug the IAC but it is difficult. It feels stuck. I am able to unclick it but I can't remove it. Any advice? I am scared I will break something. The prices here are so expensive compared to the U.S. And there is no where here where we can take our Jeep to get a diagnostic OBDII. We have to go to the dealership and they charge us $95 just for a diagnostic...
Anyway, any tips on how to take apart the IAC?
Thanks,
you dont "take it apart", you remove it- its not a take apart piece
theres those two little torque screws on pre-91 vehicles-unknown what you got- once those are off, it pops out-- theres an oring where it enters that stays on the IAC...usually...sometimes it stays in the TB-- the first time its removed is the hardest because the seal hasent been broke-- no worries takeing it off--just pull straight out, she`ll co-operate.

OBD11 scans per dealership here run $75 a pop just to hook up, then run flat rate/per hour- diagnosis isnt included.....Renix scans run about the same, but I have seen one run that cost $300.....you sir, are not alone.
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Old 10-18-2005, 10:14 PM   #8
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Ed,
Do you think that fuel could have anything to do with it? Is it possible that impurities in the fuel could have disturbed the fuel/oxygen ratio, causing an influx in the idle?
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Old 10-19-2005, 05:46 AM   #9
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Ed,
Do you think that fuel could have anything to do with it? Is it possible that impurities in the fuel could have disturbed the fuel/oxygen ratio, causing an influx in the idle?
usually bad gas will cause a low idle with loss of power-with pinging.
really bad gas will cause a hard start with weird idle that jumps around, with stalling......

the computer can do some timing adjustment on its own to help, but usually not enough with bad,bad gas.

I still hink its either the IAC or a vacuum leak-maybe at the TB base...maybe on one of the vac lines. Some automatics have that duel sensor TB...one for the TPS, one for the tranny...
there was a recall on earlier models for high idle...havent checked your year yet though...
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Old 10-19-2005, 08:22 AM   #10
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Quote:
Originally Posted by Ed in North Ga.
usually bad gas will cause a low idle with loss of power-with pinging.
really bad gas will cause a hard start with weird idle that jumps around, with stalling......

the computer can do some timing adjustment on its own to help, but usually not enough with bad,bad gas.

I still hink its either the IAC or a vacuum leak-maybe at the TB base...maybe on one of the vac lines. Some automatics have that duel sensor TB...one for the TPS, one for the tranny...
there was a recall on earlier models for high idle...havent checked your year yet though...

What Ed said!
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Old 10-19-2005, 05:52 PM   #11
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ok this is sorta on the same topic..and sorta a hijack.. powers that be can do as they will.. sorry
I got a 03 auto mangler and usually when its cold when Il driving up the street it feels like the car is surging.. ;ie kinda like someone tapping the accellerator softly but quickly
any ideas on what might be the cause of this?
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Old 10-19-2005, 06:20 PM   #12
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ok this is sorta on the same topic..and sorta a hijack.. powers that be can do as they will.. sorry
I got a 03 auto mangler and usually when its cold when Il driving up the street it feels like the car is surging.. ;ie kinda like someone tapping the accellerator softly but quickly
any ideas on what might be the cause of this?
a few things come to mind...got to get the first one out of the way>

check your rearview mirror next time it happens. midgets love to sneak behind jeeps and shove them....and no one knows why....

ok...if its happening really fast, it could be a faulty injector/plug/wire/cap/rotor.....do the standard tune up- new plugs, check the ohms on the wires, replace the cap and rotor button-retest.

hollar back.

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