Engine stuttering is not normal, and is usually related to the engine not receiving fuel, vacuum, air or a faulty sensor. If you have recently worked on your car, you may want to re-look at the areas that you were working in to see if perhaps an electrical connection or a hose may have been bumped loose. Otherwise, here are some of the more common reasons that the VW loses power while driving.
Issue: My engine TDI stalls and dies while driving. I can restart it, and it runs as if there has never been a problem.
What to do:
- The sensors on the Volkswagen can be extremely sensitive, and if they detect the slightest problem, they can shut the system down as a safety measure. The ECU needs to be checked for diagnostic codes.
- You may have a loose electrical connection within your engine compartment. If your check engine light is on, it is a good bet that it is an electrical connection or a sensor that is going bad. These two parts send information to the ECU, and when that information is intermittent like a connection that comes and goes, the ECU will shut the engine down as a safety precaution. Check to see if you can tell if there is a disconnected wire or a loose battery cable.
- An ECU that is going bad can cause the vehicle to die, but allow it to restart. There are two modes to the ECU: full drivability and limp mode. In limp mode, the ECU has detected a problem and gives you just enough power to limp to the dealership. You will want to have a diagnostic run on the vehicle once you have it in the service department.
Issue: My VW hesitates while driving and then dies. It is hard to restart.
What to do:
- You may have encountered bad fuel. In that case, you will want to drain the tank completely and change the fuel filter. After you drain the fuel, check for water in the fuel.
- You may have a loose connection with a vacuum line. You can check the hoses to make sure they are all connected, then start the engine and listen for whistles or hisses that would indicate a leak in a hose. You may even try wiggling a hose to see if there is a change in the sound of the engine, but use extreme caution when doing so as the engine is hot and has moving parts.
- You can check the vacuum in the cylinders to determine whether the valve or ring seals are properly set. A seal that is leaking can cause hesitation in the engine and a very rough engine idle.
Issue: My TDI runs rough or will not start at all and expels blue smoke.
What to do:
- You have a dirty diesel engine filter. It will prevent fuel from getting to the engine, so you need to change it. When it gets this dirty, you may not be able to start the engine at all, so change this as soon as possible.
While there are several reasons that an engine would cut out while driving, the most common reason is a faulty sensor of some sort. If you find yourself on the highway or in traffic and your vehicle cuts out, you may be able to restart it while you are still coasting. This would be the safest way to get back to speed. Otherwise, pull safely off the road and out of traffic before trying to restart it.