IAC Sensor - JeepForum.com
 
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post #1 of 13 Old 07-20-2013, 06:33 AM Thread Starter
elemon5601
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IAC Sensor

I have a 95 zj laredo V8 and i was seeing if anyone knew how to tell if the IAC sensor is going bad. It idles perfect sitting still in drive, but when i put it in park it jumps up to 1500-1700 rpm.

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post #2 of 13 Old 07-20-2013, 06:59 AM
dusterdude
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Could be the tps too
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post #3 of 13 Old 07-20-2013, 07:01 AM
Rich93ZJ
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Vacuum leak?
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post #4 of 13 Old 07-20-2013, 07:45 AM
Uniblurb
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Have you cleaned the IAC? If not that's a good place to start along with removing/cleaning the whole throttle body. You should clean the inside of the housing the IAC is located in real thoroughly but don't need to remove it from the throttle body. Here's a real good write-up on how to do it. Just don't move or twist the pintel while cleaning it.

http://www.jeepforum.com/forum/f13/h...4/#post7047001

When removing the cables from the throttle body just twist the throttle plate linkage to create some slack. Also make sure you disconnect the neg cable on the battery whenever disconnecting any sensor.
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post #5 of 13 Old 07-20-2013, 07:45 AM Thread Starter
elemon5601
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how could i tell if it was the tps?
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post #6 of 13 Old 07-20-2013, 08:15 AM
Uniblurb
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Have you checked for any error codes using the key trick yet? Turn ignition switch quickly from off-on-off-on-off-on then count the flashes on your display. There will be a short delay between the 1st number and the 2nd one. You can usually ignore the first one if it's 12 (believe it may mean your battery has been disconnected in the last 50 ignition turn-ons) and number 55 which is the end of the test. Believe a faulty reading from the TPS will give code 24 meaning voltage may be too low or high. Believe I have the procedure/codes correct and someone can correct me if I'm wrong.

Below is a test you can use for checking TPS voltage when back-probing the connector with the key on but not started. You'll need a multimeter set to DC voltage to do this test.

BTW, this test is good for both the 4.0 & 5.2/V8's.
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post #7 of 13 Old 07-20-2013, 11:44 AM Thread Starter
elemon5601
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how can i tell if the IAC is going bad?
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post #8 of 13 Old 07-20-2013, 11:47 AM
JasonStebbins
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Erratic idle.

Poop
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post #9 of 13 Old 07-20-2013, 11:58 AM Thread Starter
elemon5601
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it idles at 1500 rpm in park most of the time but will sometimes drop to 500 rpm or even lower but will go back to 1500 after i cut it off and then start it back up again
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post #10 of 13 Old 07-20-2013, 01:15 PM
Uniblurb
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Quote:
how can i tell if the IAC is going bad?


Quote:
Originally Posted by elemon5601 View Post
it idles at 1500 rpm in park most of the time but will sometimes drop to 500 rpm or even lower but will go back to 1500 after i cut it off and then start it back up again
Aren't these the same 2 things you asked about/said in your 1st post?

Did you check for codes? Have you thought about cleaning the IAC or are you just going to go buy a new one? Have you checked the voltage on the TPS to see if it's bad?

Electronic troubleshooting on these ZJ's is not an exact science and you need to try some of things I posted to try to help you out. If not, we're just wasting our time here...

Edit: sorry to seem kind of harsh and know you're young/new to the forum. But at least acknowledge posts where someone had to do some research for your specific problem. Don't have a multimeter? We can help you out in showing where to buy one for $20-$25 and guide you through on how to use it. Just trying to say communications is a 2-way street in seeking help through the forum. Welcome and good luck!
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post #11 of 13 Old 07-20-2013, 05:58 PM
coralman
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Gotta break em in right Uni, Surprisingly, the throttle body and IAC don't have to be that dirty to make an idle difference. Mine wasn't, but after cleaning it smoothed my idle a good bit.

Info on projects and repairs categorized by system
http://www.jeepforum.com/forum/f13/c...-faqs-2863665/

Originally Posted by HighLonesome
lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
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post #12 of 13 Old 07-20-2013, 09:11 PM Thread Starter
elemon5601
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i checked them both the TPS wasn't reading like you said it should be so we went ahead and ordered both for 40 bucks, i think/ hope that should do it. Thanks everybody
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post #13 of 13 Old 07-20-2013, 10:39 PM
Uniblurb
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Quote:
Originally Posted by coralman View Post
Surprisingly, the throttle body and IAC don't have to be that dirty to make an idle difference. Mine wasn't, but after cleaning it smoothed my idle a good bit.
Agree coralman and cleaning the throttle body/IAC smoothed my idle out too. Believe it also improved my gas mileage a little but my IAC was filthy.


Quote:
Originally Posted by elemon5601 View Post
i checked them both the TPS wasn't reading like you said it should be so we went ahead and ordered both for 40 bucks, i think/ hope that should do it. Thanks everybody
You're welcome and hope replacing them fixes your problems. In the future, or if you continue to have the same problem, only go with Mopar sensors. They're a lot more pricey but cause a whole lot less grief in the long run. Good luck!
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