wmburns
SN Certified Technician
Here is a case where the details matter. This thread has mentioned P1504 and P1506 DTC codes. There is a HUGE difference between the two. One is a wiring FAULT. The other could be as simple as an incorrectly adjusted idle set screw.
Yes your Mach 1 has an idle set screw.
Yes your Mach 1 has two throttle return springs.
Expect problems as long as the IAC is disconnected. It is not possible to use the idle adjust screw to correctly control the idle. If by some change you do get it to work, it will get out of adjustment when the weather changes.
Expect idle problems as long as the idle does not drop to abnormally low levels when ever the IAC is disconnected. Ideally in an application with the non black vented IAC, the motor should DIE when the IAC is disconnected.
If this were my car, I would disconnected the IAC electrical connector and then close the idle stop screw until the motor begins to run abnormally slow. IF the motor does not slow, THEN there's a vacuum leak allowing air to enter the motor from somewhere. STOP and find out where.
Then reconnect the IAC valve. Test drive. If the idle shows signs of improving, back the idle adjustment out more until the motor dies with the IAC disconnected. Be sure to turn the key off and back on after each adjustment. This is needed to reset the TPS initial position.
BUT at no point in time should you ever back the idle set screw out to the point where the throttle when closed does not POSITIVELY rest on the idle stop screw. This step is IMPORTANT.
Yes your Mach 1 has an idle set screw.
Yes your Mach 1 has two throttle return springs.
Expect problems as long as the IAC is disconnected. It is not possible to use the idle adjust screw to correctly control the idle. If by some change you do get it to work, it will get out of adjustment when the weather changes.
Expect idle problems as long as the idle does not drop to abnormally low levels when ever the IAC is disconnected. Ideally in an application with the non black vented IAC, the motor should DIE when the IAC is disconnected.
If this were my car, I would disconnected the IAC electrical connector and then close the idle stop screw until the motor begins to run abnormally slow. IF the motor does not slow, THEN there's a vacuum leak allowing air to enter the motor from somewhere. STOP and find out where.
Then reconnect the IAC valve. Test drive. If the idle shows signs of improving, back the idle adjustment out more until the motor dies with the IAC disconnected. Be sure to turn the key off and back on after each adjustment. This is needed to reset the TPS initial position.
BUT at no point in time should you ever back the idle set screw out to the point where the throttle when closed does not POSITIVELY rest on the idle stop screw. This step is IMPORTANT.
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