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89 jeep cherokee "renix" high idle when warm.

Old 06-12-2011, 05:29 PM
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Default 89 jeep cherokee "renix" high idle when warm.

I've done multiple searches on the renix high idle when warm, but I have a symptom that I have yet to find in the search. When you first start the jeep up in the morning, she'll idle around 1000. Once the temp gauge reaches the white notch between 100 and 210 she will then idle around 1200. Here's the odd part. I took her on the highway today to go to pick in pull to pick up an HVAC vacuum canister. After getting off the highway, she'll idle at 1500. When you stop the engine and start it back up the idle goes to 1200. When the jeep hits 210, the idle returns to 1000. The jeep will only hit 210 on a hot day * No idea what stat is in her, but i'm going to replace with a 195. I'm an OEM kind of guy* I know the vacuum lines are good, and I did tighten the intake bolts. Maybe it's time to bust out the volt meter.
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Old 06-12-2011, 06:04 PM
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check how dirty the iac is and check for vacuum leaks
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Old 06-12-2011, 07:04 PM
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Dirty or misfunction IAC motor on the throttle body can have an intermitent high idle symptom. Try cleaning the cone and seat (gently with your best friends toothbrush and some carb cleaner, don't get rammy with the cone). If that doesn't fix it; I last paid $125 at Napa for new, part# 2-1771. Check out Freegdr's link, he has great links.
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Old 06-12-2011, 07:09 PM
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PS: As a last resort: Since the idle adjust screw is factory trapped and not adjustable, I have before bent the throttle tab with an adustable wrench to change the idle speed. Be gentle and a small adustment goes a long way.
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Old 06-12-2011, 08:08 PM
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I'll replace the IAC this weekend. Trust me, she's 100% clean. I've noticed one thing. The vacuum line coming out of the cruse control has no vacuum to it.
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Old 06-12-2011, 08:29 PM
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Do a seafoam treatment. Make sure ALL the vacuum lines are good, if they look old, just replace them.

Do a new t-stat (I do 182 summer, 195 winter) and while your at it, flush the coolant system and clean the coolant temp sensor, those can cause weird things in the ECU idle circuit.
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Old 06-12-2011, 08:36 PM
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Not fair! Everyone already stole my answers!
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Old 01-05-2014, 12:05 PM
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Default Well, did it work???

Well, I realize this post is from years ago, but it seems my Jeep has suffered from high idle ever since I bought it 8 years ago. I recently removed and cleaned my throttle body, but still has high idle. I was wondering if the new IAC CPTslackass bought fixed the problem.
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Old 01-05-2014, 12:30 PM
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Originally Posted by peep View Post
PS: As a last resort: Since the idle adjust screw is factory trapped and not adjustable, I have before bent the throttle tab with an adustable wrench to change the idle speed. Be gentle and a small adustment goes a long way.
Don't ever do that!!!
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Old 01-05-2014, 12:32 PM
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Originally Posted by csmgj View Post
Well, I realize this post is from years ago, but it seems my Jeep has suffered from high idle ever since I bought it 8 years ago. I recently removed and cleaned my throttle body, but still has high idle. I was wondering if the new IAC CPTslackass bought fixed the problem.
If it's always done it, I would verify the throttle body butterfly stop screw position FIRST. Someone like peep coulda messed with it before you got it. Here's how.



Cruiser’s Renix Throttle Body Butterfly Adjustment

Okay. Let's start from scratch. First off, that's not an idle adjustment screw. It's a throttle butterfly stop screw. It's purpose is to allow the butterfly to be as close to completely closed as it can be without binding or wearing into the throttle body. It was never intended to be adjusted in the field. But, Uncle Bob didn’t know that, did he?

Engine off. Back off the butterfly stop screw with a 3/32” allen wrench until the butterfly is completely closed. Now. turn the screw in until the FAINTEST movement of the butterfly opening is detected. This can be done more easily with the throttle body removed. If you remove the throttle body, be sure to replace the gasket underneath it after thoroughly cleaning the old one off.

Revised 07/07/2012
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