Losing Power in a Volkswagen TDI
This event could happen with no warning. It can happen to just about any car. However, this hub focuses on the problem for diesel cars, This is not to say that the items to consider causing the problem will be found on non-diesel engines, they can.
The problem can be more mysterious if you have no loss of power on flat or slight hills and occurs mostly on steep hills or climbs. A steep hill can be close to 40%, between the bottom and top and how long the distance is, The shorter the distance between them the steeper the grade is.
Diesel cars made prior to 2005 produced more soot and tended to gather in key parts of the engine. Over time, they would clog reducing the air flow into the engine. Thus, for diesel cars loss of power can be attributed to clogged intake manifold and EGR. Check to make sure either is not clogged restricting air flow. Another frequent issue is the MAF, which regulates the air flow into the car from the air filter. These sensors can fail without any warning or reason. They may be fine on level roads, yet, start to fail on steep roads. Another sure clue is that your engine light appears indicating something needs to be looked at. Sometimes, these can reset and go off, but, if it comes back on, have it checked out.
All cars have a MAF. The following items can cause a loss of power, there can be multiple interconnecting reasons. The best process is to eliminate each one until the problem is resolved.
- Bad EGR, needs replacing
- Bad turbo boost sensor or boost leak
- A leaking EGR (replace)
- Clogged exhaust (diesel only)
- Vacuum leaks (these can be very subtle or obvious, check hoses and connections)
- If you car has a turbo, check both the hot and cold side. The cold side can be fine, while the hot side is bad. If this is the case, replace turbo.
- The vacuum line for the turbo that its solenoid operates is bad- replace solenoid.
- If turbo, its actuator has failed
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