Questions and Answers
240SX Idles High
Q. I have a 1993 Nissan 240SX SE Coupe. 2.4 liter engine. Automatic transmission. 78,000 miles. Fuel Injection. After I had my car tune-up in a shop, it idles very high in cold days. Even the engine has been running for an hour, the water temperature indicator points to the middle of gauge, the idle doesn't go down (the standard is 700 RPM, but it ran as high as 1400 RPM. Sometime it was 1600 RPM). My friends told me that it is OK, and I should wait till warm season. Then change the idle back. Now the weather is getting warn (60F). The car idles drop back to 800 RPM. I don't think that the car can do it automatically. It must have some problem. Maybe the temperature sensor is too far away from the engine? I appreciate for your help.
A. Under normal conditions when you start that car cold, the cold idle will be about 1200 rpm then gradually decrease to about 650 rpm. It sounds like the base idle speed was adjusted improperly.
To adjust it, disconnect the throttle position sensor (TPS) connector. Connect a tachometer and start the engine. When the engine is in this condition (TPS disconnected), the IACV-AAC valve and the ignition timing are held in a "fixed" position, and the idle speed is called "base idle." If the engine stalls with the TPS disconnected, the base idle speed is adjusted too low. Turn the adjusting screw on the IACV-AAC valve until the engine idles at 650 rpm, plus or minus 50 rpm.
Information provided courtesy of ALLDATA
