My 1998 Nissan Sentra has a 1.6L engine and an automatic transmission. In hot weather, with or without the air conditioner on, the engine dies from time to time at low RPMS. It usually happens at a red light, or pulling into a parking space.
I had a complete tune-up, no change. The check engine light does not come on. I took it to Nissan and they said no codes showed up and they were unable to make it act up. They set the idle up a little, which only they are able to do, but the problem is still there on an intermittent basis. I'm fearful that my daughter, who drives the car, is going to be in an accident.
There are all kinds of possible causes to an intermittent stall condition. But be sure the basics have been well covered. Many vehicles accumulate carbon within the throttle body assembly which blocks the correct amount of air from entering the engine at idle. The carbon can often be removed, using the proper chemical solvents, without removing the throttle assembly from the engine.
The entire engine should also be inspected for any vacuum leaks. Then a few very important adjustments need to be performed. First, the ignition timing should be set to specifications (8 degrees BTDC). Correct timing not only keeps the engine running efficiently, but also affects idle speed and quality.
The idle speed is controlled by an IAC (idle air control) valve, which bleeds precise amounts of air into the engine to maintain the correct idle speed under various driving conditions. The IAC valve should be tested to confirm its correct operation. The minimum idle speed is adjustable by means of an adjustment screw, and must be set to specifications in order to keep the engine from stalling, even when the IAC valve is preventing additional air from entering the engine.
The TPS (throttle position sensor) voltage output changes with the throttle plate movement from the minimum idle speed adjustment, and should be the final setting performed. The TPS tells the system's computer how far your foot is into the accelerator.
All of these adjustments and procedures require minimal labor, but need to be performed correctly by a trained technician. These are the basics before continuing diagnosis, if the stalling condition still exists.