Chevy Engine Stalling? How to Diagnose the Underlying Issue

You want your engine to run smoothly, and when it does not, you want to know why and how to fix it. There are a number of reasons that your engine can be giving you trouble, but here are some things to take into consideration while you are troubleshooting the problem.

Chevy gauges

Stalls Immediately After a Cold Start

This is usually indicative of an engine that is not getting enough fuel to air mixture. Cold engines need much more fuel than a warm one, so there is a problem in the amount of gas flowing to it.

  • This could be due to a vacuum leak around the throttle body or intake manifold gasket. It can be due to a bad or loose vacuum hose. There may be a leak in the EGR or PCV valve. Replace or fix broken or loose parts.
  • You may have a dirty airflow sensor that is giving a false reading the Chevy’s computer. It can be cleaned with an aerosol electronics cleaner. That should take care of the problem.
  • The idle speed control system may be defective. This system controls the amount of air that bypasses the throttle. If it gets plugged or the solenoid valve sticks, the engine may not be getting enough air. This will cause a stall. You can clean the bypass circuit with an aerosol electronics cleaner. If that does not fix it, make sure that all the wires are connected. It may need to be replaced if you cannot find a loose wire and cleaning it does not fix it.
  • The coolant sensor may be bad. It will tell the PCM that wrong temperature and that can cause the fuel mixture to be improperly mixed. This can make the car run too lean or too rich depending upon whether the temperature is hot or cold. Replace the sensor.
  • The air temperature sensor may be bad. If the sensor is telling the PCM to let more air in than needed, the mixture is going to be wrong. Replace the sensor.
  • The MAP sensor is bad. This sensor reads the intake vacuum, and then tells the PCM how to determine engine load. If this information is wrong, then there may be too much fuel or too much air. Replace the sensor.
  • You may have low engine compression. Pistons and cylinders wear out, and then they can lose compression because they do not fit as tight as they should. Do a compression check to determine if this is the problem. You may need to overhaul or replace the engine.
  • The spark plugs are dirty. A dirty spark plug can cause a misfire, which stops the engine from running properly. Additionally, you may have a weak ignition coil or bad crankshaft position sensor. Put new plugs and wires on the engine and see if this does not fix the problem.
  • The gas is bad. Sometimes, it is possible to get gas that has too much alcohol in it. This will cause your vehicle to run poorly. If you discover that the engine runs badly after putting gas in it, then drain the tank and refill with a better quality gas.

Stalls at Light Engine Loads or Idle

This could mean that the idle speed is too low or there is a load on from other components. In addition, it could be that the fuel is not mixed properly.

  • The air conditioning compressor can be binding, which can put a load on the engine. If the problem is only when the air conditioner is on, then check your A/C for the problem.
  • This can happen if the battery is run down or there is not enough juice in the alternator. It puts a load on the engine and can pull down the RPMs. Check your battery for a charge. Replace it if it does not hold a charge.
  • Low voltage can also be a problem that can affect the ignition system, and that can cause misfires. The charging system should have between 13.5 to 14.5 volts while you are at idle.

Engine Stalls While Driving

This is usually an indication that there is an ignition problem, and there is not enough spark. It can be a faulty crankshaft position sensor. It can also mean a bad ignition coil.

  • If this happens, pull over and open your hood. Check the engine for a spark by pulling off a plug wire. Place the end of the wire near the block and let it go. It will shock you if the ignition is working. Have someone crank the engine, and look for a spark or listen for a snap from the plug wire. If you do not see or hear this from the plug wire, the problem is in the ignition.
  • Your engine could have died due to low fuel pressure. The fuel pump does not give much warning before it goes. You will not be able to restart the car. With the ignition in the ON position, listen for the fuel pump. You should hear a buzz in the area around the tank. Check the fuse to the fuel pump. It could also be the relay, but on high mileage cars, you probably need a new pump.
  • A bad PCM relay can cause this problem. If the PCM loses connectivity for a moment, it will shut down the ignition and the fuel injectors. You might try putting in new relays to see if this makes the problem go away. Check the wiring and connections for other problems.
  • Too much or too little voltage can cause the engine to stall. The PCM needs a continuous 12volts in order to operate. If there is a voltage issue either dropping below 9volts or rising over 16volts, the PCM may shut down the ignition and the fuel injection. There may be a short in the system. You may need to consult a technician or someone with a scan tool in order to read the code and isolate the problem.

As you can see, there are any number of reasons that your engine may stall. Finding and fixing the engine stall may be a little bit difficult, so if you need assistance, consult your local Chevy dealership and tell them the symptoms that surround the incident. By knowing that, they have a better chance of quickly diagnosing and repairing the problem.