If you're not sure if your engine is pumpe duse, see 1000q: pumpe duse vs. common rail and direct injection. All TDI model year 2004 -2008 sold in North America were pumpe duse. The crankshaft (which moves the pistons) uses a timing belt to drive and precisely time the camshaft (which opens the valves). While the injection timing is electronically controlled by the ECU and injector solenoids, the pressurization of the pumpe duse injectors is mechanical and by the camshaft. The camshaft sprocket has an adjustment range to adjust torsion or idle stabilization. This adjustment can drift over the life of the timing belt on pumpe duse TDI engines which is a common cause of rough idling and hard start. In North America, pumpe duse engines include the 2004-2006 Golf, New Beetle, VW Jetta TDI and 2004-2005 Passat TDI. It also includes the V10 Touareg TDI but it used a gear drive for the camshaft and not a timing belt. Europe also had some DOHC TDI engines which are slightly different.
While this may fix your rough idling, a rough idle on pumpe duse engines could also be caused by worn camshaft lobes. This was a common problem on pumpe duse TDI due to their narrow lobes. See 1000q: TDI camshaft inspection and replacement for PD engines for details. It could also be caused by faulty and unbalanced fuel injectors. The procedure for inspecting is seen below. Lastly, the dual mass flywheel could be bouncing around and causing the rough idle. See 1000q: clutch FAQ for more details. DSG automatics seem to have more problematic DMF. See 1000q: DSG FAQ for more details. General running problems could be caused by a boost leak so make sure there are no air leaks in the intake path. See 1000q: boost leak check for more details.
Checking or adjusting torsion will also give the best results after doing a timing belt job on these engines. Once the timing belt is 60-80% through its scheduled replacement interval, check it again and adjust it as necessary. Proper timing will give the least vibration at idle and give easier starting. The camshaft pulley/hub (under the sprocket which the timing belt rides on) has bent tabs on the edge of the pulley. These tabs pass by the camshaft sensor and let the car's computer know exactly where the camshaft is. There's a key on the camshaft pulley which indexes its position to the camshaft so the relationship between the tabs and the camshaft position is fixed. Rotating the camshaft and pulley not only changes camshaft timing but how the car's computer sees the camshaft timing and may affect other engine operation such as fuel injection timing.
This is not a substitute for using the special VW/Audi timing belt tools. See the timing belt articles linked below for your engine for details. The point of the camshaft pin and the hole in the toothed window on the camshaft sprocket is to get timing to where the engine will start fine and be about right, as a rough estimate, +/- 1 degrees. If you don't have access to a VCDS, just find someone later who can help you and do it when practical.
Timing belt articles
1000q: 2004-2005 Passat TDI timing belt part 1, BHW engine
1000q: 2004-2006 Golf/New Beetle and 2004-2005 Jetta TDI timing belt removal, BEW engine
1000q: 2005.5-2006 VW Jetta TDI timing belt replacement 1, BRM engine
Note - if you just replaced the timing belt, first do all final checks, start the engine, and check fluid levels before doing this procedure.
If you didn't just replace the timing belt or you're ready to start, drive the car until it's
at normal operating temperature. With the headlights/fan/electrical load
off, plug the VCDS cable into the obd2 port
and start the software. Click on the "Engine" button to enter
the engine module.
Your controller part number may vary by year/engine. Click on
Then click "Up" 4 times or enter 4 to view Group 004. The
number on block 4 is labeled "Torsion Value". Higher than 0 is
advanced timing and lower than 0 is retarded timing. The best value is
about 0-0.5. The Passat TDI appear to like about 0-0.5. Jetta TDI
appear to like .5-1.0. A
little higher by 0.5 is fine because torsion tends to slightly retard as the
belt ages. More advanced than 1.0 may give best results in your case and
adjusting the torsion by +/- 1.0 won't cause any damage, so feel free to play
with the value.
While you're here, also check the idle stabilization through injection
quantity (measuring block group 13). The car's computer can adjust the amount of fuel injected to
stabilize idle. A value more than +/- 0.5 would indicate a problem.
You could try filling the fuel filter with a can of diesel purge and
running it like that to clean out the injectors.
Shut off the engine and the car. Take care when working on the engine since it will be hot. Open the hood and remove the engine cover by pulling it straight up. It pops off with rubber ball/snap sockets. If you have a VW Passat, it's held with 3x 10mm nuts. You may be able to retrofit the snaps, see 1000q: snap cover retrofit for details.
If you have a Jetta, Golf, or VW New Beetle TDI, remove the intake hose right
before the intake flap valve. (Does not apply to Passat). There are
spring clips that hold the hose in place at each end. There may also be a
T30 torx bolt or clips along the hose for the fuel line. Make sure the
hose is free before removing it.
Remove the upper timing belt cover. It's held by 2 clips.
Loosen the 3x 13mm camshaft sprocket bolts shown below by a few turns. The bolts have oval holes on the sprocket which let the camshaft pulley (hub) rotate under the sprocket, within a range, without turning the timing belt. Do not remove the bolts all the way - just loosen them enough so that the pulley under the sprocket can rotate.
Ignore the black pin and ball in the picture below, it's from another writeup.
The toothed window can help you determine how far you rotate the camshaft.
Also note the oval bolt holes peeking out on the sides of the 3x 13mm bolt
heads. If you can't see the toothed window, use the edges of the bolt
heads as a reference to see how far you've moved the camshaft.
Do not loosen the larger center 18mm bolt. It holds the pulley underneath the sprocket to the camshaft.
Use a 18mm wrench on it and just gently tap on it to turn the camshaft a few degrees at a time. Too much and timing will move too far. Turning the bolt (and pulley) clockwise will advance timing. Counter clockwise will retard timing. Again, you're not loosening the center 18mm bolt, you're just using it to turn the sprocket. The timing belt will not move, just the pulley and the camshaft.
If you want to use a sprocket counterhold tool like shown in the video below, the direction is the opposite. In other words, if you're moving the sprocket only, turning the sprocket counterclockwise will advance timing and clockwise will retard timing.
Tighten the 3x 13mm bolts to 18 ft-lb. You can choose to wait until after you're satisfied with the final position to replace the upper timing belt cover. However, make sure that nothing or no one can get caught in the timing belt. Objects falling into the timing belt can cause belt failure and serious engine damage. If it or any other belts catch loose hair/clothing/etc., or you, it can cause serious injury. Greatly overtightening the bolts can cause bolt failure and serious engine damage so make sure you use a torque wrench.
Replace any intake hosing that was removed. Make sure all tools are clear of the engine. Restart the engine and recheck camshaft torsion through VCDS.
When satisfied, replace the timing belt cover and engine cover. Double check that any intake hose tabs and quick connect clips are secured.
Here is a video that helps explain the procedure. In this example,
timing needed to be advanced slightly after checking it to get to that 0.5 value but a tiny adjustment can
result in a 2 degree change in timing.
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