Slow idle reset to normal speed...How? - JeepForum.com
 
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post #1 of 8 Old 12-24-2018, 03:52 PM Thread Starter
Gremmy
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Slow idle reset to normal speed...How?

I need to set the slow idle to a faster speed and almost cutting out with the heater and lights on in the very cold.

Had some misfire issues with the Crank Position Sensor. Seems ok now cleaned. I read CPS post by cruiser and followed.

Is 'Slow Idle', sensor related? No idea.
Thanks

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post #2 of 8 Old 12-25-2018, 10:59 AM
cruiser54
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Quote:
Originally Posted by Gremmy View Post
I need to set the slow idle to a faster speed and almost cutting out with the heater and lights on in the very cold.

Had some misfire issues with the Crank Position Sensor. Seems ok now cleaned. I read CPS post by cruiser and followed.

Is 'Slow Idle', sensor related? No idea.
Thanks
so, this is an 87 to 90 4.0?

Ever cleaned your throttle body?

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post #3 of 8 Old 12-28-2018, 07:38 AM Thread Starter
Gremmy
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Hi cruiser 54. No never cleaned 1989 4L throttle body. Looking at the vacuum lines. All rubber connections are missing, pipes are poked in only. Where can I obtain rubber vacuum connectors?
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post #4 of 8 Old 12-28-2018, 07:45 AM
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Clean the throttle body and IAC.

THROTTLE BODY AND IAC CLEANING
OCTOBER 30, 2015 SALAD 19 COMMENTS

Originally by TJWalker of CherokeeForum & JeepForum

dirty IAC

The Idle Air Control (IAC) is mounted on the back of the throttle body (front for ’87-’90).

The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is retracted, the air control passage flows more air which raises the idle speed. When the valve plunger is extended, the air control passage flows less air which lowers the idle speed.

Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea. This should be part of a normal tune-up procedure and whenever idle/stalling issues are present.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

dirty renix throttle body

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a Torx driver (2 bolts; one can be kind of hard to get to). On ’91 and later, it may be easier to just remove the whole throttle body. Be sure to use a new throttle body to manifold gasket when reinstalling.
“Gently” wiggle out the IAC from the throttle body. Gasket/O-ring on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and oxygen sensors. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner.
It is also a good idea to clean the entire throttle body bore itself, the butterfly valve inside of the throttle body and it’s edges, and all associated linkage as long as you have things disassembled.

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post #5 of 8 Old 12-28-2018, 07:46 AM
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Check to see your intake manifold bolts are snug. Here's the harnesses for the vacuum system.

http://cruiser54.com/?p=121

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post #6 of 8 Old 01-03-2019, 10:21 PM
slickrocksteve
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Just a reminder......WEAR SAFETY GLASSES, or goggles when spraying stuff, as getting some stuff in your eyes can BLIND YOU !
Also , be careful of open flames, ( like the pilot on the hot water heater in your closed up garage !), and wear some nitrile gloves to save your skin from contact dermatitis and drying out.
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post #7 of 8 Old 01-06-2019, 11:40 AM Thread Starter
Gremmy
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Thanks all. Should I replace the MAP sensor. Read fault can cause erratic idle? I remember previously changing 'The Idle Air Control (IAC)'. I am going to try to snug intake manifold bolts, found a very minor leak, could this leak be the issue though?
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post #8 of 8 Old 01-06-2019, 01:11 PM
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Quote:
Originally Posted by Gremmy View Post
Thanks all. Should I replace the MAP sensor. Read fault can cause erratic idle? I remember previously changing 'The Idle Air Control (IAC)'. I am going to try to snug intake manifold bolts, found a very minor leak, could this leak be the issue though?
Don't change the MAP.

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