So I would like some help in diagnosing a periodic underboost issue and intermittent limp mode please.
I have an A3 8P TDI CR 2.0 140 with 118k on the clock. My driving style is more to the italian side than miss daisy and the car does primarily motorway miles (in the region of 600mi a week at the moment). The fault happens mostly in 5th/6th at low revs when demanding a large throttle input, it will drop into limp from there. Keeping the revs above 2500RPM seems to solve the problem.
The fault code coming up is P0299 Underboost.
I have changed the boost pressure sensor already with no improvement. I have also checked the vacuum line coming from this sensor which connects to turbo actuator, there is a vacuum and the actuator (at idle) does move the rod freely (with about 10~13mm of movement) downwards when the vacuum is applied at idle. I have yet to check that the actuator can hold a vacuum, but will be testing this today as I am borrowing a vacuum kit.
My question to fault find is of multiple parts.
1. How much should the actuator move the rod to the vane arm on the turbo, is the movement I mentioned above the right amount or should it be moving more than this? The movement is clean and doesnt stick from what I can tell so I am trying to rule out stuck vanes.
2. How is best to go about finding a vacuum leak for the entire system? I am happy on testing the actuator but more wider ranging than this I have no idea where to start.
3. Could an EGR valve issue be causing this underboost? If I am lucky enough that the turbo is fine with the moment side of things from the actuator, where else could the problem lie?
I have an A3 8P TDI CR 2.0 140 with 118k on the clock. My driving style is more to the italian side than miss daisy and the car does primarily motorway miles (in the region of 600mi a week at the moment). The fault happens mostly in 5th/6th at low revs when demanding a large throttle input, it will drop into limp from there. Keeping the revs above 2500RPM seems to solve the problem.
The fault code coming up is P0299 Underboost.
I have changed the boost pressure sensor already with no improvement. I have also checked the vacuum line coming from this sensor which connects to turbo actuator, there is a vacuum and the actuator (at idle) does move the rod freely (with about 10~13mm of movement) downwards when the vacuum is applied at idle. I have yet to check that the actuator can hold a vacuum, but will be testing this today as I am borrowing a vacuum kit.
My question to fault find is of multiple parts.
1. How much should the actuator move the rod to the vane arm on the turbo, is the movement I mentioned above the right amount or should it be moving more than this? The movement is clean and doesnt stick from what I can tell so I am trying to rule out stuck vanes.
2. How is best to go about finding a vacuum leak for the entire system? I am happy on testing the actuator but more wider ranging than this I have no idea where to start.
3. Could an EGR valve issue be causing this underboost? If I am lucky enough that the turbo is fine with the moment side of things from the actuator, where else could the problem lie?