Throttle Body Screw Set Procudure - Ford Mustang Forum
 
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post #1 of 7 (permalink) Old 03-18-2011 Thread Starter
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Throttle Body Screw Set Procudure

I don't know what brand throttle body I have and I don't know the the default screw position. I get slight idle surges when first starting the car, doesn't matter if it cold or warm. It will surge about 3 times like it's finding the right idle and then stop. TPS is set right. What I'm unsure of is the IAC. When the car is iding I can disconnect the IAC and there is no change in idle, however when I first set the idle with the IAC disconnected it did change by disconnecting the IAC. I have a hunch the problem is the screw causing the the TB blade not to return to the correct position or not return to the same position all the time and perhaps letting in too much air and is now bypassing the IAC and causing the surges. It's also of course possible the IAC is not working correctly.

Before dumping $100.00 into a IAC that may or may not fix the problem I want to make sure the TB screw is set correctly and that the TB is opening and closing properly without and slack or binding.

Without knowing the brand of the TB to find their screw set procedure how do I set the TB screw properly to ensure the TB blade is functioning properly.

92 LX
Holly Systemax, Shorty Headers, TFS Stage 1 Cam, TFS FAC 170 Heads, Cobra Transmission, King Cobra Clutch
RWHP 317

2006 Mustang GT
JLT CAI and a Custom Tune
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post #2 of 7 (permalink) Old 03-19-2011
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The base idle reset procedure will take you through everything. However, the screw is fixed in the position its in (til you turn it) thus would not give a surging idle and/or no response from the IAC. Most likely you need to replace it. Surging idle could also be a vacuum leak.

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post #3 of 7 (permalink) Old 03-19-2011 Thread Starter
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Quote:
Originally Posted by spdjnky_42 View Post
The base idle reset procedure will take you through everything. However, the screw is fixed in the position its in (til you turn it) thus would not give a surging idle and/or no response from the IAC. Most likely you need to replace it. Surging idle could also be a vacuum leak.
I have turned the screw in the past and I believe that's when my problems started. This is why I'm trying to get it back to the proper position.

92 LX
Holly Systemax, Shorty Headers, TFS Stage 1 Cam, TFS FAC 170 Heads, Cobra Transmission, King Cobra Clutch
RWHP 317

2006 Mustang GT
JLT CAI and a Custom Tune
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post #4 of 7 (permalink) Old 03-19-2011
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I understand but it holds the blade open in a fixed position surging is more and less air getting to the cylinders. The screw allows the same amount of air the IAC is what controls more or less air.
Base Idle Reset Procedure

1. Clean TB with carb cleaner and nylon brush (toothbrush size). Engine off, fully open TB blade and spray/brush TB until all gunk and oil residue is cleaned.

2. Allow to dry, or close TB blade and start engine until it clears all carb cleaner fumes/liquid.

3. Let engine idle...if it doesn't, increase idle speed via TB stop screw until engine stays idling on its own.

4. Disconnect IAC valve, if engine dies repeat 3 with IAC disconnected.

5. Set idle speed to the lowest setting possible between 650-850 rpms with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, etc once the IAC is connected as follows.

6. Turn engine off, and reconnect IAC

7. With Ign On Eng Off, check TPS voltage output....if it's between .8vdc - 1.0vdc, it's OK. This voltage check should be done between the Green and Black wires at the TPS side connector as shown in the pic below (FYI: Green = TPS Signal, Black = SIGRTN, and Orange = VREF)....(-) terminal of the DVOM on the Black wire and (+) terminal on the Green wire.



8. Disconnect battery (-) for 3-4 minutes.

9. Reconnect battery, start engine, allow it to idle for 2-4 minutes to confirm setup,

10. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.

11. Turn engine off for 20 seconds, re-start engine and repeat 9 - 11 if required.

12. Reconfirm TPS output is within the .8vdc - 1.0vdc range optimum range.

NOTES:

1. No need to reset ECM KAM (reset computer), the TPS minimum value used for idle control, is reset automatically by the EEC-IV every time the ign is cycled on-off for 20 seconds-on.

2. If the TPS output is within 6vdc - 1.1vdc, it's still acceptable, since no TPS failure codes will be generated, and it falls within the EEC-IV .5vdc - 1.19vdc working range.

13. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).....you're done!

When the green light drops...
The Bullsh!t stops. :shiny:
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post #5 of 7 (permalink) Old 03-19-2011
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if this doesnt stop the rolling idle issue it can be the clutch sensor on the pedal under the dash there is a video on the internet floating around of a guy bypassing the plug with a paper clip and instantly the surge goes away


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post #6 of 7 (permalink) Old 03-19-2011 Thread Starter
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Quote:
Originally Posted by spdjnky_42 View Post
I understand but it holds the blade open in a fixed position surging is more and less air getting to the cylinders. The screw allows the same amount of air the IAC is what controls more or less air.
Base Idle Reset Procedure

1. Clean TB with carb cleaner and nylon brush (toothbrush size). Engine off, fully open TB blade and spray/brush TB until all gunk and oil residue is cleaned.

2. Allow to dry, or close TB blade and start engine until it clears all carb cleaner fumes/liquid.

3. Let engine idle...if it doesn't, increase idle speed via TB stop screw until engine stays idling on its own.

4. Disconnect IAC valve, if engine dies repeat 3 with IAC disconnected.

5. Set idle speed to the lowest setting possible between 650-850 rpms with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, etc once the IAC is connected as follows.

6. Turn engine off, and reconnect IAC

7. With Ign On Eng Off, check TPS voltage output....if it's between .8vdc - 1.0vdc, it's OK. This voltage check should be done between the Green and Black wires at the TPS side connector as shown in the pic below (FYI: Green = TPS Signal, Black = SIGRTN, and Orange = VREF)....(-) terminal of the DVOM on the Black wire and (+) terminal on the Green wire.



8. Disconnect battery (-) for 3-4 minutes.

9. Reconnect battery, start engine, allow it to idle for 2-4 minutes to confirm setup,

10. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.

11. Turn engine off for 20 seconds, re-start engine and repeat 9 - 11 if required.

12. Reconfirm TPS output is within the .8vdc - 1.0vdc range optimum range.

NOTES:

1. No need to reset ECM KAM (reset computer), the TPS minimum value used for idle control, is reset automatically by the EEC-IV every time the ign is cycled on-off for 20 seconds-on.

2. If the TPS output is within 6vdc - 1.1vdc, it's still acceptable, since no TPS failure codes will be generated, and it falls within the EEC-IV .5vdc - 1.19vdc working range.

13. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).....you're done!

I have gone through this procedure. I set the id;e w/o the IAC connected to about 650. When I started the car is idled great for about 7 minutes and it begn to surge out of no where while idling and would not stop. For some reason my car will not die with the IAC disconnected no matter how far you turn the screw.

Does this procedure remain the same for cars with cams and other mods ?

92 LX
Holly Systemax, Shorty Headers, TFS Stage 1 Cam, TFS FAC 170 Heads, Cobra Transmission, King Cobra Clutch
RWHP 317

2006 Mustang GT
JLT CAI and a Custom Tune
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post #7 of 7 (permalink) Old 03-19-2011 Thread Starter
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Quote:
Originally Posted by MelloStang View Post
if this doesnt stop the rolling idle issue it can be the clutch sensor on the pedal under the dash there is a video on the internet floating around of a guy bypassing the plug with a paper clip and instantly the surge goes away
Sorry but what do you mean by rolling idle surge?

92 LX
Holly Systemax, Shorty Headers, TFS Stage 1 Cam, TFS FAC 170 Heads, Cobra Transmission, King Cobra Clutch
RWHP 317

2006 Mustang GT
JLT CAI and a Custom Tune
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