Power loss Folks: I have an 03 tdi that has a loss of power and this is the story. Initial loss a couple of months ago. Check engine codes showed coolant temp sensor fault. Replaced this as well as Mass air flow sensor. Little better with coolant temp sensor but still loss especially when accelerating up hill. Replaced fuel filter, no change. Finally broke down and took it to dealer last week and was told manifold plugged with carbon. They cleaned manifold, replaced EGR cooler and EGR valve. Also replaced timing belt for maintence. Seemed a little better when I left the shop and then once I was on the road to work 200 miles away, I realized that the same issue stands. Poor acceleration, no power on hill. Also noted that the beautiful bum from the turbo that I used to hear was absent. SO.. My thoughts after review are 1) Vaccume leak 2) turbo is shot 3) Injectors are plugged (The injector pump was replaced at 70000. Now I have 142K on the rig. Any ideas on direction to go. I will be taking it back to dealer once I get home. Thanks

Or it could just be the waste gate stuck in the open position.

Or it could just be the waste gate stuck in the open position.

Both the EGR and the O2 sensors could be removed and cleaned, just a bit messy. Both would and could be coated with carbon deposits causing them to get incorrect readings and therefore send erroneous triggers to the onboard computer.

Though I still think that the turbo issue is a strong possibility especially with the possible stuck open wastegate. Incidentally, the wastegate is a bypass, sort of regulator, to allow the exhaust gases a means of escape and not spin the turbo; normally at over 10PSI boost.


Both the EGR and the O2 sensors could be removed and cleaned, just a bit messy. Both would and could be coated with carbon deposits causing them to get incorrect readings and therefore send erroneous triggers to the onboard computer.

Though I still think that the turbo issue is a strong possibility especially with the possible stuck open wastegate. Incidentally, the wastegate is a bypass, sort of regulator, to allow the exhaust gases a means of escape and not spin the turbo; normally at over 10PSI boost.

Equipment required

Accurate boost gauge, length of hose, hose connectors.

Connection

Check the manufacturer's data to establish the boost pressure limits.

On the majority of petrol engine vehicles, the boost reading is taken from the inlet manifold.

Connect the boost gauge hose into a convenient take-off pipe on the inlet manifold. Ensure that the connection is after the throttle butterfly valve (a vacuum will be present with the engine ticking over).

Do NOT connect boost gauge hose into brake servo vacuum line.

Carefully route the boost gauge hose back to the dashboard. Do not allow hose to foul throttle linkage or any other moving parts i.e., cooling fan, alternator or water pump.

Connect the boost gauge to the hose and place in a convenient position which can easily be read from the driving position.

Testing



Drive the vehicle until a normal water temperature reading is attained.

Choose a long straight empty road (preferably with a gentle incline). Steady the engine speed to around 3000 rev/min and select either third or fourth gear, depending on road speed.

Using your left foot on the brake pedal, gently increase throttle whilst applying the brakes to maintain 3000 revs/min.

When full throttle is reached at 3000 rev/min check the boost reading on the gauge.

If the boost pressure requires adjustment, consult the manufacture's recommendations.

IMPORTANT NOTES:





If, whilst taking a boost reading, pinking or detonation is audible from the engine, the test should be aborted to prevent damaging the engine.




This test will overheat the vehicle's brakes in a short time. The test procedure must be conducted within five seconds to prevent brake fade.




Only conduct testing on a private test ground or closed road.
Equipment required
Accurate boost gauge, length of hose, hose connectors.
Connection
Check the manufacturer's data to establish the boost pressure limits.
On the majority of petrol engine vehicles, the boost reading is taken from the inlet manifold.
Connect the boost gauge hose into a convenient take-off pipe on the inlet manifold. Ensure that the connection is after the throttle butterfly valve (a vacuum will be present with the engine ticking over).
Do NOT connect boost gauge hose into brake servo vacuum line.
Carefully route the boost gauge hose back to the dashboard. Do not allow hose to foul throttle linkage or any other moving parts i.e., cooling fan, alternator or water pump.
Connect the boost gauge to the hose and place in a convenient position which can easily be read from the driving position.
Testing
Drive the vehicle until a normal water temperature reading is attained.
Choose a long straight empty road (preferably with a gentle incline). Steady the engine speed to around 3000 rev/min and select either third or fourth gear, depending on road speed.
Using your left foot on the brake pedal, gently increase throttle whilst applying the brakes to maintain 3000 revs/min.
When full throttle is reached at 3000 rev/min check the boost reading on the gauge.
If the boost pressure requires adjustment, consult the manufacture's recommendations.
IMPORTANT NOTES:

If, whilst taking a boost reading, pinking or detonation is audible from the engine, the test should be aborted to prevent damaging the engine.
This test will overheat the vehicle's brakes in a short time. The test procedure must be conducted within five seconds to prevent brake fade.
Only conduct testing on a private test ground or closed road.