QuestionMy Hyundai Excel 94 engine stops working when I decrease the driving speed to zero at idle. It only happens some times. At other times, it runs normally. So I am not sure what the problem is. Could you help? Thanks.
AnswerYour idle is controlled by an electric motor that actually opens and closes the throttle. Carboning of the throttle body can affect the system's adjustment, and the system is also known to have problems with wiring.
If your check engine lamp is on, you should first address those issues. To read the diagnostic trouble codes, you'll either need to take the car to the dealer or use an analog voltmeter (with needle) to read the trouble codes using the procedure in the shop manual. The shop manual can be viewed at www.hmaservice.com (requires Internet Explorer). Once you've registered for a free account and logged in, the information on how to read the trouble codes is in the fuel section of the shop manual.
If there are no trouble codes, I'd recommend cleaning the throttle body and adjusting the motor position sensor using the procedure in the shop manual. It's imperative that you look in the manual because the idle adjustment screw is difficult to find. Here's the basic procedure:
1. Clean the throttle body with carburetor cleaner or similar agent.
2. Start the car and run until it runs smoothly at operating temperature.
3. Ground the connector for adjustments.
4. Start the car.
5. If the car stalls, adjust the idle screw (clockwise) and restart the car. Continue until the car stays running.
6. Adjust the idle screw until the idle speed is at the preferred value.
7. Screw the throttle stop screw slowly clockwise until the idle switch opens (testing with voltmeter or test light).
8. Unscrew the throttle stop screw 1/2 turn counter-clockwise.
9. Verify the idle switch is closed.
10. Adjust the throttle position sensor to 500mV (checking with a digital voltmeter).
11. Remove the ground from the connector for adjustments.
