new info that might help: looking at the picture of the TB, it doesnt look the same as ours. It might be a picture of the TB from the 2.0 motor. If our TB's have this same air bypass passage, you might want to check and see if it is getting gunked up or something.
IDLE AIR CONTROL MOTOR
The Idle Air Control (IAC) solenoid is mounted on
the throttle body. The PCM operates the idle air control
solenoid (Fig. 27). It is an electric stepper solenoid.
The PCM adjusts engine idle speed through the
idle air control solenoid to compensate for engine
load, coolant temperature or barometric pressure
The throttle body has an air bypass passage that
provides air for the engine during closed throttle idle.
The idle air control solenoid pintle protrudes into the
air bypass passage and regulates air flow through it.
The PCM adjusts engine idle speed by moving the
IAC solenoid pintle in and out of the bypass passage.
The adjustments are based on inputs the PCM
receives. The inputs are from the throttle position
sensor, crankshaft position sensor, coolant temperature
sensor, MAP sensor, vehicle speed sensor and
various switch operations (brake, park/neutral, air
conditioning and power steering).
When engine rpm is above idle speed, the IAC is
used for the following functions:
˛ Off-idle dashpot
˛ Deceleration air flow control
˛ A/C compressor load control and power steering
(also opens the passage slightly before the compressor
is engaged so that the engine rpm does not dip
down when the compressor engages)
Target idle is determined by the following inputs:
˛ Gear position
˛ ECT Sensor
˛ Battery voltage
˛ Ambient/Battery Temperature Sensor
˛ MAP Sensor
Fig. 27 Idle Air Control Solenoid—Typical