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Old 06-07-2021, 08:07 PM   #1
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Default Idle issues ----Computer under the Seat ?

Hey Buds,

I've been working on getting my 4 CLY, D21 in running shape.

Its coming along EXCEPT for the pain-n-arse Idle issue???

IDLE goes 'up and down' all the time---- even when i'm driving i can feel/hear it (although more pronounced when i stop at light).

Looks like there are 3 components in the Throttle body area (Two which i have changed).






-Changed MASS sensor (b)
-Changed IACV Solenoid (c)
-(looking to change IDLE VALVE) (a)


ALSO looking at the computer under the seat as being an CAUSE???


ANY ONE having LUCK figuring the Idle issue out?


Thanks for your help...

Last edited by Balkins; 06-08-2021 at 12:42 AM.
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Old 06-07-2021, 10:11 PM   #2
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First thing you need to do is to check the computer for any codes. The one part you have not changed is the thermal element and it's job is to raise the idle when the engine is cold, than as the coolant warms up and runs through the thermal element housing it causes the idle to drop to the RPM it should be. If the thermal element is bad, the idle will stay high, and a bad thermal element would not cause a fluctuating idle.


Highly recommend to replace EVERY vacuum line, the rubber is old now being the truck was made so long ago, a small crack or split in a vacuum hose can cause issues. Best to replace one hose a t a time so you don't get any mixed up.


I would clean the inside of the throttle body also, pay attention to the edge of the butterfly and the inside of the TB where the butterfly sits against. I use TB cleaner a toothbrush and a clean rag.
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Old 06-08-2021, 12:43 AM   #3
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Quote:
Originally Posted by ahardb0dy View Post
First thing you need to do is to check the computer for any codes. The one part you have not changed is the thermal element and it's job is to raise the idle when the engine is cold, than as the coolant warms up and runs through the thermal element housing it causes the idle to drop to the RPM it should be. If the thermal element is bad, the idle will stay high, and a bad thermal element would not cause a fluctuating idle.


Highly recommend to replace EVERY vacuum line, the rubber is old now being the truck was made so long ago, a small crack or split in a vacuum hose can cause issues. Best to replace one hose a t a time so you don't get any mixed up.


I would clean the inside of the throttle body also, pay attention to the edge of the butterfly and the inside of the TB where the butterfly sits against. I use TB cleaner a toothbrush and a clean rag.

What size Hoses would you buy and How much?


Thanks for the Tips!


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Old 06-08-2021, 12:58 AM   #4
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10 foot of 3/8-inch for the vacuum hoses, I believe.

But your issue sounds like what is called HUNTING in the EC section of the service manual.
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Old 06-08-2021, 01:03 PM   #5
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Originally Posted by jp2code View Post
10 foot of 3/8-inch for the vacuum hoses, I believe.

But your issue sounds like what is called HUNTING in the EC section of the service manual.

Service Manual?


Nah...didn't get that one----bought the Truck used about 20yrs ago.


....
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Old 06-08-2021, 01:42 PM   #6
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Originally Posted by Balkins View Post
Service Manual?


Nah...didn't get that one----bought the Truck used about 20yrs ago.


....
The link is below in my signature.
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