No power and rough running when throttle pushed

There are several possible reasons why the turbo on your 2002 Golf TDI might not be engaging:

1. Boost pressure issue: The most common cause of a non-engaging turbo is a boost pressure issue. This can be caused by a leak in the intake system, a damaged turbocharger, or a clogged air filter.
2. Malfunctioning wastegate: The wastegate is a component that controls the amount of exhaust gas that flows through the turbocharger. If the wastegate is malfunctioning, it may not allow the turbo to engage properly.
3. Faulty turbocharger control solenoid: The turbocharger control solenoid is responsible for regulating the amount of pressure that goes to the turbocharger. If the solenoid is faulty, it may not be able to control the pressure properly, leading to a non-engaging turbo.
4. Electrical issue: There may be an issue with the electrical components of the turbo system, such as a faulty wiring harness, sensor or control module.

To diagnose the problem, you can check for any visible leaks in the intake system or damage to the turbocharger. You can also check the wastegate for proper function and inspect the turbocharger control solenoid for any signs of damage or failure. If you are unsure how to perform these checks, it is recommended to take your vehicle to a qualified mechanic for a proper diagnosis and repair.

Have the car scanned for fault codes. A power loss in a turbo motor can be caused by simple vacuum leaks. You can check for loose piping and clamps. There are various components in that car that could cause such a problem. These include the turbocharger itself, the turbo boost (N75) valve, wastegate and its linkage, the car's ECU, maybe even a non turbo fault like a clogged catalytic converter or vehicle misfire.

If all power is lost in the car, it could indicate a bad battery connection, bad wiring, or loose main wire harness, etc.

If a warning light comes on - it may be going in to Safe Mode.

Safe mode is the set of parameters that the car will use if it believes there
is a fault with the engine that could cause irrepairable or long term damage.

Generally it is an excess in expected boost pressure entering the engine.
This excess boost from the turbo tends to happen for 4 reasons.

The boost pressure sensor (MAP sensor) is faulty.
The wastegate is seized shut or slightly open.
The wastegate actuator is faulty.
The air line to the wastegate actuator is damaged or off.

Obviously, if the sensor is faulty, it will tell the ECU lies about the boost pressure.
If the wastegate assembly fails in any way it will fail to open to bypass the turbo.
The turbo will continue to spin up, increasing the boost pressure, causing the fault.

Initially I would suggest disconnecting the battery for 5 minutes (make sure you know your
radio code before doing this), this will turn safe mode off and your car should run normally
again. Drive home with a bit of care, you may find the car might never do it again. If it does
go into safe mode again, you know you have a real problem and not just a glitch.

Best to contact your dealer and have it checked out.

Fault Code 35
Description: Radiator fan relay circuit is open or shorted
Power loss light: Off
Limp-in mode: None

Possible Causes:
Bad connection or wiring - Check the wiring and connections between the logic module and the relay. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.

Bad relay - Disconnect the relay and apply 12V across the coil terminals (between the white wire and either of the other two terminals on the small connector). You should hear a click for either of the two termials and the connection between the grey wire and the other two terminals of the large connector should be shorted.

Diagnostic Method
Trigger Parameters
- Near 0V or near 12V not detected when the relay is turned on or off, respectively
Results If Component Fails
Fault code 35 is stored.


Fault Code 45
Notes: For Turbo models only

Description: Turbo boost limit exceeded
Power loss light: On
Limp-in mode: None

Possible Causes
Vaccum leak - Check all vaccum lines between the wastegate actuator, manifold, and wastegate solenoid. Also check the line to the MAP sensor. Repair or replace any bad lines.

Wastegate solenoid failure - The wastegate solenoid is located in the right, front fender next to one to three other solenoids. See the Understanding Solenoids page.

Bad connection or wiring - Check the wiring and connections between the logic modle (or SMEC) and the wastegate solenoid. Clean and regrease any corroded connectors with dielectric grease and repair any shorts. This condition may be accompanied by a code 36.

Wastegate actuator spring failure - Try to slide the wastegate to wastegate actuator push rod into the actuator. It should not move. Try to pull it out. If it pulls out with little effort (even if it springs back in), replace the actuator.

Jammed wastegate - Disconnect the wastegate actuator pushrod and swing the wastegate arm on top of the turbo. It should have about a 50 degree swing. Make sure the lever and push rod are clear of any obsticles that may cause them to jam (the heat shield below the fuel rail is a major culprit).

Diagnostic Method
Trigger Parameters
- MAP sensor output voltage has exceeded overboost cut-off point



Following years are probably the same as 1987, but I don't have any hard data to back that up. Some have said that 4.74V was the max for Turbo I engines of later years. Some information indicates that the Turbo II with an automatic had a cut-off of 4.96V, but I don't know of any Turbo II vehicle that had an automatic transmission.

Results If Component Fails
A fault code 45 is stored, the power loss light is turned on, and the fuel injectors are shut off. Once the boost has fallen to 3 psi to 5 psi, the fuel injectors are turned back on and the power loss light is turned off. The overboost cut-off point for a particular vehicle depends on the year, engine, and transmission.


Keep us updated.

check the turbo wastegate, if it overboosts the ecu reduces or cuts fuel not to do any damage in the engine. I read this http://www.discovery2.co.uk/wastegate.html and after a while i saw your problem and thought that this was the problem.

If you are getting zero boost, then your wastegate actuator may be jammed, causing the wastegate to be stuck open. That'll bleed all the boost off around the turbine, straight to the exhaust, and you'll never build any boost pressure.

check wastegate(round valve on turbo)is working it may be loosing vacuum,or you have an electrical issue with the boost controler,but check wastegate first as its easier and could be the problem

You have blown a turbo charge pipe somewhere, check all hoses...Once this happens the car will begin to run very rich, as evidenced by the black smoke. Do not continue to drive like this, as the raw unburned fuel in the exhaust will clog the catalysts and that can be very expensive.

probably a bit late to reply, but i had exactly same problem and now my engine has seized up, so please get it checked out immediately by Audi service center.

The turbo never "engages". The turbo spins all the time, but the amount of exhaust gas driving it is adjusted by the wastegate.

The problem you are experiencing could be due to the wastegate's vacuum tube being disconnected. The wastegate is meant to open as the inlet manifold pressure increases, so that the turbo spins less and doesn't compress the air too much. It could also be the result of a faulty sensor, but check the vacuum tubes first. Your wastegate actuator is fitted just behind the turbo. If the pipe has come off recently, you should be able to see a clean section where it's meant to be joined to the actuator. The disconnected pipe should be fairly close by. Again, the pipe should be connected to the inlet manifold though from memory I think this is one of the difficult to reach pipes on the back of the engine.

As a side note, the turbo guage on the dashboard is very poor. Even if only for the sake of diagnostics, you should get a cheap direct vacuum driven guage.