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post #1 of 9 (permalink) Old 02-17-2007, 12:42 PM Thread Starter
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Idle question

I searched, but only saw posts regarding newer models. In my 89, is the idle adjustable in drive? Or is it also controlled by the ECU, just like all the others?


-Brian
1989 Mercury Cougar - Anything but the Ordinary

Fully Built 4.2 Coming Soon, Parts include:
SC Block, 4.2 Crank, Scat H Beam Rods, Wiseco Pistons, Custom Comp Cam, 3/8 Main Stud Girdle, Ported/Polished Split Port Heads and Lower Intake, Windstar Upper, Heavier Springs, 1.73 Roller Rockers, BBK Valve Covers, Kooks long tube headers, Aluminum Radiator.

It May Not Be Pretty When Finished, But It'll Perform Pretty Darn Well.
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post #2 of 9 (permalink) Old 02-17-2007, 02:54 PM
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Controlled by the ECU.

--Chris

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post #3 of 9 (permalink) Old 02-17-2007, 07:12 PM
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On the throttle body you can adjust the idle speed by turning a adjustment screw. This will give you a different idle speed but over time the ECU will compensate for it and will return itself to a pre-determined idle provided the idle wasn't manually raise or lowered significantly.
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post #4 of 9 (permalink) Old 02-17-2007, 10:34 PM Thread Starter
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Ok. About the screw, where is that set to? Mine is barely touching the bracket that its supposed to move. I wonder if mine isn't in the right position?


-Brian
1989 Mercury Cougar - Anything but the Ordinary

Fully Built 4.2 Coming Soon, Parts include:
SC Block, 4.2 Crank, Scat H Beam Rods, Wiseco Pistons, Custom Comp Cam, 3/8 Main Stud Girdle, Ported/Polished Split Port Heads and Lower Intake, Windstar Upper, Heavier Springs, 1.73 Roller Rockers, BBK Valve Covers, Kooks long tube headers, Aluminum Radiator.

It May Not Be Pretty When Finished, But It'll Perform Pretty Darn Well.
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post #5 of 9 (permalink) Old 02-17-2007, 11:15 PM
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Don't mess with the idle screw, because once you fix the problem that was causing the idle, it'll be screwed up and you'll fight it forever.

Josh Keady

1994 Super Coupe ('93 5.0L swap), 1990 Tbird 3.8L, 1982 Honda CB900F, 1972 F-100 SportCustom 4x4, 1970 Chevy Custom Camper / 20
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post #6 of 9 (permalink) Old 02-17-2007, 11:17 PM Thread Starter
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I don't ever remember touching the screw since I purchased the car. Is there certain position that it is supposed to be set at, like when it came from the factory? I don't know if the previous owner would have ever messed with it.


-Brian
1989 Mercury Cougar - Anything but the Ordinary

Fully Built 4.2 Coming Soon, Parts include:
SC Block, 4.2 Crank, Scat H Beam Rods, Wiseco Pistons, Custom Comp Cam, 3/8 Main Stud Girdle, Ported/Polished Split Port Heads and Lower Intake, Windstar Upper, Heavier Springs, 1.73 Roller Rockers, BBK Valve Covers, Kooks long tube headers, Aluminum Radiator.

It May Not Be Pretty When Finished, But It'll Perform Pretty Darn Well.
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post #7 of 9 (permalink) Old 02-17-2007, 11:37 PM
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Yes, there is a certain position. That screw is not an idle adjust screw like so many people misconceive it to be. It is the adjustment on the throttle body that allows a calibrated minimum amount of air to pass the throttle plate and it prevents the throttle plate from sticking in the bore. This setting must be precise as all of the PCM's calculations are based on this being at a certain setting. I don't know about your car for sure but to give you an idea of my car, that screw was tampered with a while back and to get it back to it's appropriate spot, I had to place a 0.002" feeler gauge between the throttle arm and the screw and adjust the screw until it just touched the feeler gauge. Then I had to turn an additional 1/2 turn to establish the proper setting. This procedure was obtained from the Ford service manual.

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post #8 of 9 (permalink) Old 02-18-2007, 12:02 AM Thread Starter
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So from your setting, the screw was just barely touching the throttle arm when set correctly?

This is why I am asking. I purchased an underdrive crank pulley. I installed that the other day, along with a new alternator with a smaller pulley, to help with the charging. When the car is in park or drive with no lights on, the voltage is fine. In drive, with fog lights and/or headlights, the voltage drops down into the 12's. Once I start moving, the lights brighten and the volts go back up.

I thought getting the smaller alternator pulley would have helped with any problems. I guess it is not worth having an underdrive pulley on a daily driven car if it is going to cause voltage problems like this.


-Brian
1989 Mercury Cougar - Anything but the Ordinary

Fully Built 4.2 Coming Soon, Parts include:
SC Block, 4.2 Crank, Scat H Beam Rods, Wiseco Pistons, Custom Comp Cam, 3/8 Main Stud Girdle, Ported/Polished Split Port Heads and Lower Intake, Windstar Upper, Heavier Springs, 1.73 Roller Rockers, BBK Valve Covers, Kooks long tube headers, Aluminum Radiator.

It May Not Be Pretty When Finished, But It'll Perform Pretty Darn Well.

Last edited by th3subtl3on3; 02-18-2007 at 12:09 AM.
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post #9 of 9 (permalink) Old 02-18-2007, 12:18 AM
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Yeah, the screw isn't making the throttle plate move very much. Don't get me wrong, the screw is making full contact with the arm. It just isn't pushing the throttle plate open very much.

--Chris

DirtyDog Torque Converter For Sale!!
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