Adjust Idle Speed - JeepForum.com

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post #1 of 25 Old 03-04-2004, 11:58 AM Thread Starter
dwills898
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Adjust Idle Speed

Does anyone know how to adjust the idle speed on a 93 grand cherokee, I cleaned my Idle Air Control and now it idles better, but still to low. I want to increase the idle speed. It idles around 500 rpm.

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post #2 of 25 Old 03-04-2004, 12:01 PM
ZickZJ
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Quote:
Originally Posted by dwills898
Does anyone know how to adjust the idle speed on a 93 grand cherokee, I cleaned my Idle Air Control and now it idles better, but still to low. I want to increase the idle speed. It idles around 500 rpm.

You can't adjust it, its electronically controlled by the IAC. Around 500 rpms is about normal for Grand Cherokees for some reason.

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post #3 of 25 Old 03-04-2004, 12:29 PM Thread Starter
dwills898
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Originally Posted by ZickZJ
You can't adjust it, its electronically controlled by the IAC. Around 500 rpms is about normal for Grand Cherokees for some reason.
Yes but the iac is controlled by the main computer, and the IAC can only adjust to a certain point.
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post #4 of 25 Old 03-04-2004, 12:38 PM
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Mine idles at 750 on the mark. No fluxuating.
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post #5 of 25 Old 03-05-2004, 07:44 AM
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so does anyone know of somewhere that can reprogram the 'puter?

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post #6 of 25 Old 03-05-2004, 02:27 PM
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why do you need to adjust it?

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post #7 of 25 Old 03-05-2004, 07:25 PM
Choff
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Could be worse... I replaced the O2 sensor on mine and now it idles at 1700!
No idea how to fix that...
'93 4.0L
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post #8 of 25 Old 03-06-2004, 01:12 AM Thread Starter
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Quote:
Originally Posted by Saleen4971
why do you need to adjust it?
It is to low and causes vibration.
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post #9 of 25 Old 03-06-2004, 09:07 AM
MikeRuth
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Quote:
Originally Posted by dwills898
It is to low and causes vibration.
I don't know if this helps but on my 94 GC there is a mechanical stop on the manifold. Now it is in such a position that a normal tool(screwdriver, etc)can not be used, I'm guess there is a special service tool that can be used or some creativity.
No doubt if you raise that screw the idle will be higher.
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post #10 of 25 Old 03-06-2004, 09:10 AM
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Quote:
Originally Posted by Choff
Could be worse... I replaced the O2 sensor on mine and now it idles at 1700!
No idea how to fix that...
'93 4.0L
After replacing the O2 sensor and having a high idle I would guess the output of that sensor is incorrect for the computer.

Disconnect the battery for 1 hour and reconnect it. that will reset the computer. After doing that on my 94 Cherokee I had to drive it around the block a couple times to get the idle to come back to normal, as it was a bit low.
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post #11 of 25 Old 03-06-2004, 09:21 AM
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It can be done manually ...There is a small cap on the passenger side of the throttle body when looking from the front..
Pop out the metal cap and there is a torx screw under that .... It will open up the butterfly which in turn raises your Idle..

I have a pic in my stupid imagestation account but I cant post it..



Here you go .. I transfered it to my personal website..

Good luck..

Carl

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post #12 of 25 Old 03-06-2004, 12:11 PM Thread Starter
dwills898
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Quote:
Originally Posted by Swamp Boy
It can be done manually ...There is a small cap on the passenger side of the throttle body when looking from the front..
Pop out the metal cap and there is a torx screw under that .... It will open up the butterfly which in turn raises your Idle..

I have a pic in my stupid imagestation account but I cant post it..



Here you go .. I transfered it to my personal website..

Good luck..

Carl

Wich one in the picture is it?
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post #13 of 25 Old 03-06-2004, 06:11 PM
Meerkat
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Quote:
Originally Posted by dwills898
Wich one in the picture is it?

If the plug is intact, I really must caution against adjusting this screw...
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post #14 of 25 Old 03-06-2004, 07:48 PM Thread Starter
dwills898
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Quote:
Originally Posted by wvd
If the plug is intact, I really must caution against adjusting this screw...
This is looking from the front of the vehicle right, and why do you caution against it?
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post #15 of 25 Old 03-06-2004, 08:38 PM
Meerkat
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Quote:
Originally Posted by dwills898
This is looking from the front of the vehicle right, and why do you caution against it?

Yes, it's from the front of the vehicle.
If the plug is intact, then it's likely nobody has messed with the screw behind it. The engine's idle speed is determined by several inputs: air conditioning, power steering, cold and warm running, etc. If one or more of the inputs used to set the idle speed is wrong, then compensating for it by adjusting that screw is only masking the real problem. Are you positive the AIC is operating properly? There is a test procedure in the Haynes manual to check the AIC. It also says that if the AIC tests good, then the PCM is suspect.

Warren
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