Air Leak or hose has come off from MAP sensor
Unlikely. A faulty IAC will give you poor, erratic idle speed.
I blown head gasket can cause an engine miss which one cause a rough idle.
Pontiac 1993 vehicles have been known to have Fuel Pressure Regulators that when they fail, they will release too much fuel to the intake and therefore produce erratic or Idle up and down. Also, the erratic Idle can be caused by a air pressure leak located as part of the Emissions system.
If there is an erratic cold idle the car could be experiencing a vacuum leak. Check all the air hoses on the vehicle and replace what is worn. Improper air pressure will lead to an unstable idle.
erratic idle can most times be tracked to a vacuum issue, check all your lines for leaks
might be bad motor mount / or electrical short
Idle speed is not adjustable. It is controlled by the engine copmuter. If your idle speed is too high or low you have a problem with a sensor or the idle air controll actuator. Also, a weak battery can cause the idle too be erratic
Erratic idle is usually caused by a dirty or faulty IAC (Idle air control) . This is located right at the throttle body. The IAC sometimes can be removed and cleaned (internally) with a intake manifold type cleaner, but this is not always successful.
If there is an erratic idle then the idle air control valve can be malfunctioning. First perform an engine diagnostic to see if there are any malfunctioning sensors. The ECU will the be able to determine if the idle air control valve is broken.
Driver error.
There is no idle screw. The idle air control valve controls the idle and can be set on different settings. You should consult a Ford dealer or mechanic for proper settings.
where is the idle control motor for a 1998 ford escort