Remember that when the engine is cold at around 70 C, the engine runs in warm up mode resulting in high idle and advance timing to attain warm up state. Once the temperature exceeds the warmup benchmark, everything is set to normal by the ECM. The RPMS in warmup mode should be at-least 1200, if it is not, the IAC valve is missing some steps. There are two possibilities, but before that you should have AVO meter and a copy of service manual so that you can refer to the exact location of the sensors described below:
The AC Signal switch/wire is faulty. To check the function of switch, check the continuity using AVO Meter while turning the AC 'ON' and engine started. (The AC signal switch harness has two wires brown and yellow). It should show connected when AC is 'ON' and disconnected when AC is 'OFF'. If it is fine then proceed further.
Check for TPS voltage. Attach black pin of AVO meter to the black wire and the red pinn to the blue wire of TPS and switch 'ON' the ignition key. It should deflect 0.5 volts at idle. Now push the throttle to max (off-course engine OFF, just ignition 'ON'), the reading should be >4.0 v. If the reading are not in the above range, the TPS will be maladjusted and/or faulty.
Remove the IAC valve from the TB, while the harness still attached. Switch 'ON' the ignition. You should see the spindle of IAC valve moving (1 cm). If the movement is very minor, the IAC valve is faulty.
Check the Coolant Temperature Sensor (CTS) voltage. Attach the black pin of AVO meter to the black wire of CTS and red pin to the yellow wire and start the engine. The voltage should be >3.5 on cold engine that should gradually decreased to <1.0 volt when the engine is hot while at optimum temperature around 1.5-2.0V.
If all of the above check are fine, reset the ECM by removing the fuse/negative battery terminal. Wait for 10 seconds and follow the idle learning procedure as mentioned below:
