Idle Air Control Problem? [VIDEO]
Professional
Joined: Nov 2012
Posts: 216
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From: Manitoba, Canada
Here is how to set the MINIMUM idle speed from the Autozone repair guides.
The key here being, setting the minimum idle speed is a last resort after you have verified all the items listed above are checked to be working properly. I recommend you sign up to Autozones site, or download some factory service manuals and go through the AIS/IAC troubleshooting steps to check for issues with it, they will have you checking voltages to the motor and checking for proper operation. Replace it if it is suspect, don't try and use a bandaid to cover up the fact that it doesn't work.
Unlike carbureted vehicles, the fuel injected engines covered in this information do not require idle speed adjustment checks as a part of a regular tune-up. In fact normal idle speed is NOT adjustable and should not be attempted. Base idle speed is controlled by the engine controller (computer).
This adjustment is the minimum idle speed with the Automatic Idle Speed (AIS) closed.
Before adjusting the idle on an electronic fuel injected vehicle, the following items must be checked (and corrected, if necessary):
AIS motor operation
Engine vacuum and/or EGR leaks
Engine timing
Coolant temperature sensor operation
Connect a tachometer and timing light to the engine, according to the manufacturer's instructions.
Close the AIS by using ATM tester C-4805 or equivalent, and ATM test code #03.
Connect a jumper to the radiator fan, so that it will run continuously.
Start and run the engine for 3 minutes to allow the idle speed to stabilize.
Check engine rpm and compare the result with the specifications listed on the underhood emission control sticker.
If idle rpm is not within specifications, use tool C-4804 or equivalent to turn the idle speed adjusting screw to obtain 790-810 rpm. If the underhood emission sticker specifications are different, use those values for adjustment.
If idle will not adjust down check for binding linkage, speed control servo cable adjustment or throttle shaft binding.
Turn the engine OFF , then disconnect the tachometer, reattach the AIS wire, and remove the jumper wire from the fan motor.
This adjustment is the minimum idle speed with the Automatic Idle Speed (AIS) closed.
Before adjusting the idle on an electronic fuel injected vehicle, the following items must be checked (and corrected, if necessary):
AIS motor operation
Engine vacuum and/or EGR leaks
Engine timing
Coolant temperature sensor operation
Connect a tachometer and timing light to the engine, according to the manufacturer's instructions.
Close the AIS by using ATM tester C-4805 or equivalent, and ATM test code #03.
Connect a jumper to the radiator fan, so that it will run continuously.
Start and run the engine for 3 minutes to allow the idle speed to stabilize.
Check engine rpm and compare the result with the specifications listed on the underhood emission control sticker.
If idle rpm is not within specifications, use tool C-4804 or equivalent to turn the idle speed adjusting screw to obtain 790-810 rpm. If the underhood emission sticker specifications are different, use those values for adjustment.
If idle will not adjust down check for binding linkage, speed control servo cable adjustment or throttle shaft binding.
Turn the engine OFF , then disconnect the tachometer, reattach the AIS wire, and remove the jumper wire from the fan motor.
Thread Starter
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All Star
Joined: Jun 2011
Posts: 858
Likes: 2
From: Pinellas County, FL
I wish I knew what lines were vacuum, I know I can bypass the step with the electric fan because mine is mechanical however I do not have an ATM tester. I will start by borrowing a tach so I can at least get a ballpark here, and sign up at AutoZone. Thanks!
Professional
Joined: Nov 2012
Posts: 216
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From: Manitoba, Canada
Autozone has vacuum line diagrams that should help you as well.
Most of your vacuum lines should be originating from your throttle body, and will branch out from there. They will be black rubber hoses, and if they are original to the truck they are probably hardened and cracking. Vacuum leaks can cause all kinds of fun issues such as erratic idle, high idle, blower vents changing functions based on throttle position, 4WD engagement issues, etc.
Most of your vacuum lines should be originating from your throttle body, and will branch out from there. They will be black rubber hoses, and if they are original to the truck they are probably hardened and cracking. Vacuum leaks can cause all kinds of fun issues such as erratic idle, high idle, blower vents changing functions based on throttle position, 4WD engagement issues, etc.
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All Star
Joined: Jun 2011
Posts: 858
Likes: 2
From: Pinellas County, FL
Yeah everything is original 1988 and sat in a dry barn for 12 summers untouched, if the lines are all the same ID I can buy a roll of hose and just redo them all if it's cheap enough.
any vacuum lines on the throttle body and intake should be vacuum lines. if your 88 is anything like mine the vacuum line running from the booster will go to a huge "t" type fitting on the intake manifold which should help too.
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All Star
Joined: Jun 2011
Posts: 858
Likes: 2
From: Pinellas County, FL
AutoZone has a confusing website, it claims there are no repair manuals for the 1988 Dakota...where are you looking? I was told before I could find wiring diagrams there for my truck but still am yet to find anything, I already had an account with them.
i stopped going to autozone because the ones by me are only part look up jockies who don't know what they are doing. every time i ordered something they shipped it to the store one town over(the other store did the same thing) and denied it ever being shipped or being received. and advance auto parts lays everyone off every 2 months and hires incompetent people(problem former autozone employees). i use napa or oriellys and the library for vacuum diagrams
Professional
Joined: Nov 2012
Posts: 216
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From: Manitoba, Canada
If you are just replacing hoses you shouldn't even need a vacuum diagram really, just find the vacuum hoses coming off your intake/throttle body and replace them one by one. I wouldn't recommend removing all of them at once, as it will make it tougher to get them all back ran the way they were.
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All Star
Joined: Jun 2011
Posts: 858
Likes: 2
From: Pinellas County, FL
You would get a laugh out of my local Advance Auto Parts...80% of the staff are blonde chicks that go uhh, yes? Yes is this right? Like a damn foreign speaking individual, always new too. That's why we have Car Quest and Consumer Auto Parts
Veteran
Joined: Dec 2011
Posts: 433
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From: Knoxville, TN
eeeesh...You guys got some bad luck in the parts stores..i swear by my advanced auto that i go to, same guys have been there for as long as i can remember, me being 24 and remembering back to 6-7 years old. The guys at mine are old retired mechanics, legit REPAIR mechanics, not all these newbie replace types.