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Nissan 240SX Rough Warm Idle

Q. Vince, I have a 1993 Nissan 240SX, great car, with 134,000 miles. It starts every time, but as of late it starts fine and runs okay while cold then it has a rough idle with hesitation when you mash the gas. But it seems to smooth out if I keep the rpm above 3,500. What do think?


Nissan 240SX Rough Warm Idle

A. As embarrassing as it is, there was only one car in my career that I could not fix. And it was a Nissan 240SX. But I didn't feel so bad because six other Nissan Techs before me couldn't find what was wrong and later, after Nissan bought the car back, the Nissan Techs and Engineers couldn't find what was wrong either.

I would start out with the simple stuff. A good tune up with distributor cap and rotor, new ignition wires and a fresh set of NGK spark plugs. BKR5E-11 gap between 0.039" and 0.043". I highly recommend NGK plugs in this engine, it makes a big difference.

Then I would give the throttle body a good cleaning. The throttle body and Idle Air Control Valve (IACV) gets gummed up with junk and cause all kinds of idle problems. Read Cleaning Throttle Bodies for instructions on how to do this.

In addition the valve clearance is adjustable on that engine so the idle problem could be caused by a tight valve. You might want to let a Nissan dealer do the valve clearance check and adjustment.

This in itself could very well take care of the idle problem. If it doesn't, and there are no codes stored in the PCM, then I would suspect a bad Coolant Temperature Sensor.

Nissan 240SX Rough Warm Idle

Additional Information provided courtesy of AllDATA

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