Is your car engine dying at slow speeds or at stops signs? Does the idle speed fluctuate up and down before the engine dies? These can be common symptoms of a dirty throttle body in need of cleaning. The throttle body basically regulates the fresh air flow coming into the engine from the air cleaner box. There is a vane/valve at the entrance to the throttle body which opens and closes with the accelerator position inside the vehicle.
Over time the vane or valve becomes gummy with dirty and varnish build up from gasoline vapors etc. This gumminess causes the vane to hang up and not close fully. This in turn changes the air flow going to the engine. The onboard computer sees this as a problem and tries to compensate the idle speed to make up for the loss of air flow. This causes an erratic idle sometimes referred to has hunting and pecking, since the tachometer gauge shows the RPM needle moving radically up and down trying to find a happy medium to keep the engine running.
In worst cases the idle speed can not be maintained and the engine dies, mostly at slow speeds and at stop signs with your foot on the brake in gear. Even shifting from forward to reverse can cause the engine to die.
What can you do to remedy the situation? Ask your mechanic to clean the throttle body with some gentle fuel injector cleaner and use a rag or tooth brush to remove the varnish and gummy build up inside and around the vane. This is a cheap and easy repair and can usually be done while you wait. We charge about $75 in my shop to do this, and it should be performed as regular maintenance about every 30,000 miles.