How to Troubleshoot Stalling in GM Vehicles

The problems causing GM car stalls might not always be under the hood.

Gasoline powered GM cars need the same basic requirements to run as any other cars with gas engines. The most basic needs are fuel, air and ignition. A car can stop running, or stall if any of these elements is not delivered correctly to the car's engine. In addition to these basic requirements, cars have a host of electronic and computerized devices that can also fail. So troubleshooting a stalling GM or any other can become much more involved than just basic delivery of fuel, air and ignition.

Things You'll Need

• Flashlight
• Wrenches
• Screwdrivers
• Ratchet and socket set
• Rubber mallet
• Automotive code reader
• Vehicle maintenance manual

Instructions

Idle Stalls

1. Inspect the intake boot and vacuum hoses at the engine. Look for worn, damaged or missing hoses. If there is a leaking vacuum hose, the loss of vacuum could cause the car to stall. Listen for a whistling noise from the hoses while the car is running. This may lead you to the leaky hose. Replace any hoses that have lost integrity.

2. Check the throttle body and idle air control motor for deposits. If there is buildup here, it should be professionally serviced. Electric throttle bodies must be cleaned very carefully.

3. Remove the exhaust gas recirculation (EGR) valve. Check the valve by pushing air into the intake port. Clean or replace the EGR valve if air can travel from the intake port to the output port. This indicates the valve is stuck open due to malfunction or carbon deposits.

4. 

   Problems with an automatic transmission can actually cause the engine to stall.

   Test the torque converter in cars with automatic transmissions if the car shutters before it comes to a stop then stalls. Check this by putting the car in neutral as you think it is about to stall. Have the torque converter replaced if the car stalls in neutral. This does require removing the transmission.

Driving Stalls

1. 

   Checking fuses with a test light can be faster than removing and visually inspecting them.

   Check all the vehicle fuses with a test light. The fuses have service ports on their tops. Attach a ground from the light to a known grounded source and insert the test light probe into each service port of every fuse. If the light only illuminates at one side of the fuse, then replace the fuse.

2. Attach a code reader to your vehicle and check for trouble codes. The connector for the code reader should be easily accessible under the dash. The code reader will prompt you in the steps for checking codes once you plug it into the connector. You can rent or even borrow a code reader from most auto parts shops. Fix any problems that may directly lead to the vehicle stalls.

3. Check the fuel system pressure. Attach a test gauge onto the vehicle's fuel rail. There is usually a test port for this purpose. The gauge should read between 40 and 55 psi on most fuel injected cars. Check the fuel pump fuse and pump relay if pressure is low. Hold your fingers over the relay while someone cranks the engine. You should feel the relay click. Also inspect the relay wiring. Replace the fuse or relay if needed

4. Check power to the fuel pump if the fuse and relay check good but there is low pressure. Use a wiring schematic to find the power feed wire to the fuel pump. The wiring harness is near the fuel tank. Pierce the probe through the wire insulation while grounding the lead. Replace your fuel pump if the light illuminates but fuel pressure is low. Replace the relay if the light does not illuminate.

5. Check the ignition system or have it professionally checked. The ignition system controls combustion of gasoline in the engine. Testing the system can be a long and complex task. Use your specific vehicle's repair guide for directions.

6. Locate and check the car's power control module (PCM) relay. Visually inspect the relay contacts. The relay is probably functioning if the contacts don't look burned or ashen.

7. Inspect battery cables and posts. Clean any corrosion from the battery posts. If a cable is loose, remove it and clean the cable connector as well as the battery post. Then reinstall the cable securely.

8. Check the muffler and catalytic converter by hitting them with a rubber mallet while the engine is cold. Remove either component for inspection if you hear what sounds like rocks rattling. Replace either component if it has broken or faulty interior components.

9. Locate the ignition switch power output wire and secure a test light probe to the wire, possibly with tape. Ground the other test light lead and start and drive the car. The test light should be illuminated while the car is driving. The switch is probably faulty if the light goes out.

References

• 2 Car Pros: Engine Stalls While Driving
• Repair Pal: Throttle Body Service
• 2 Car Pros: Service Engine Soon or Check Engine Light On or Flashing?