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Old 12-18-2010, 05:00 AM
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Default Adjust Idle

Recently purchased a S10 4.3 vortec, does anyone know how to adjust the idle ?
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Old 12-18-2010, 06:45 PM
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Default IAC sensor

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Originally Posted by unique_w View Post
Recently purchased a S10 4.3 vortec, does anyone know how to adjust the idle ?
Think I found what I was asking -

The IAC (idle air control) sensor is a small motor on the throttle body that screws a giant needle valve (pintle) up and down. It regulates how much air is allowed to bypass the closed throttle plate, thereby controlling the idle speed. It moves up for example when you turn the a/c on, to kick it from the usual 900 to 1100 rpms. It's movement is controlled by the PCM (power-train control module), to maintain the desired idle speed.

The throttle body consists of... the throttle plate itself, the IAC motor (idle air control), attachments for vacuum lines, and a TP (throttle position) sensor to tell the computer what percentage the throttle is open.
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Old 01-04-2011, 08:22 AM
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Default Idle Problems Help or Advice

My 2002 S10 pickup 4.3 V6 has had idle problems (stalling at a every stop light), I did some research and thought it could be the IAC sensor, decided to take it to a shop and have diagnostics performed, with no service engine light the computer indicated it was the Mass Air Flow Sensor they replaced it and cleaned the throttle body, which stopped it from stalling. But the idle still is not right yet, I see a dip at times below 400 rpm (and the idle seems to be erratic at times) and I don't hear or see an increase in RPM when I put the A/C on Max.

I owned a 1997 S15 V6 from 97 to 06, hence I am somewhat familiar with the how the 4.3 performs and idles.

I am wondering if I should replace the IAC sensor or check to see if it has carbon on it as stated in thread "Random High Idle". The computer does not indicate any other problems, but the exhaust fumes do not smell right to me, its hard to explain the odor, it is not the rotten egg odor.

Can anyone provide any advice or suggestions ?

Thanks
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Old 01-04-2011, 01:23 PM
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Try replacing the coolant temperature sensor if the vehicle seems to be running rich or has bad gas mileage. The coolant sensor puts the computer in loop mode while the engine is cold so it has excess gas to run off of. Once the vehicle gets above 140* it normally switches out of loop mode and becomes an open circuit. This tells the computer to lean the truck out and you get better gas mileage/no rich smell in the exhaust.

As for the idle problem; start checking vacuum lines for splits or cracks, check your IAC (check the ohm load on it), also the Throttle Position Sensor as they will cause a vehicle to "hunt" for RPMS or have flat spots in the acceleration as you move the pedal more.
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Sounds like you messed something up.
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Old 01-04-2011, 10:21 PM
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Default Idle problem help

Thank You for responding, with a number of possibilities this may take awhile, I am not in any rush as the S10 is not our primary vehicle, own an HHR which is our primary drive. Slowly trying to get the S10 to smile again. Replaced the jack, repaired the 3rd door handle, refurbished the wheel center hubs, replaced one mag wheel, the engine MAF sensor was replaced and throttle body cleaned, installed clear parking lights, also in the process of modifying the auto lights to prevent them from turning on in the garage, hope to post a how to with images in the future for this mod, performed it on our HHR last year.
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Old 01-04-2011, 10:48 PM
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Quote:
Originally Posted by 88Jimmy View Post
Try replacing the coolant temperature sensor if the vehicle seems to be running rich or has bad gas mileage. The coolant sensor puts the computer in loop mode while the engine is cold so it has excess gas to run off of. Once the vehicle gets above 140* it normally switches out of loop mode and becomes an open circuit. This tells the computer to lean the truck out and you get better gas mileage/no rich smell in the exhaust.

As for the idle problem; start checking vacuum lines for splits or cracks, check your IAC (check the ohm load on it), also the Throttle Position Sensor as they will cause a vehicle to "hunt" for RPMS or have flat spots in the acceleration as you move the pedal more.


the engine coolant temp sensor could cause rough idle at first until it warms up.. outta the loop as you said ^^.. i had to replace it on my 4.3 cause it was running like shit; rough idle, bad gas mileage, and running rich.. but once i replaced the ect it got a lot better..
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Old 01-04-2011, 11:29 PM
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Default ECT Location

Engine Coolant Temperature (ECT) location drawing attached
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File Type: jpg ECT-Sensor-V6.jpg (44.2 KB, 17 views)
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Old 01-04-2011, 11:57 PM
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Default IAC Location

Isn't the IAC located on the rear of the throttle body for the 4.3 V6 ?

See attached drawing.
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File Type: jpg IAC-Sensor-V6.jpg (97.6 KB, 20 views)
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Old 01-05-2011, 12:17 AM
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no it should be on the intake manifold towards the front of the engine to the left of the thermostat housing.. well on the older model it is..
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Old 01-05-2011, 12:19 AM
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have you pulled the iac valve to check for carbon build up.. and from the first diagram you posted it seems to be else where from what i described.. im not sure ab vortec engines..
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