Adjusting the Throttle Butterfly Valve

Important Note:-

This document is only a translation of the german document from the website.

I, Phil Ade have never tried to do any of the following myself.

This document was translated in my own words by myself, Phil Ade on Saturday 11th February 2006.

Adjusting the Throttle Butterfly Valve:-

The idle speed adjustment screw is normally preset at the factory and should never be changed unless it really is necessary. If however the screw has either been accidentally adjusted or has come loose then the air intake unit must be adjusted correctly.


Key to fig. 1:-

1 = Accelerator Lever End-stop

2 = Idle Speed Adjustment Screw

5 = Accelerator Cable Clamp Bolt

6 = Accelerator Cable

Fig.1 Air Intake Unit viewed from its left-hand side.

To adjust the throttle butterfly valve correctly, unscrew the idle speed adjustment screw until you can just about see a gap between the accelerator lever end-stop (1) and the idle speed adjustment screw (2).

Now check the gap with a thin piece of paper, it should just about fit into that gap. Now turn the adjustment screw ½ turn clockwise (inwards). The accelerator lever should now be correctly adjusted.

Now check to see if the throttle butterfly valve (shown in fig. 2) is completely closed.

[Image] Key to fig. 2:-

1 = Accelerator Lever End-stop

2 = Idle Speed Adjustment Screw
(here you see it origional with paint on it for locking)

7 = Throttle Butterfly Valve

8 = Air Intake Temperature Sensor

9 = Accelerator Potentiometer

Fig. 2 Air Intake Unit viewed from above

The value of the accelerator potentiometer must now be checked. This can be checked by using any of the following diagnostic tools:-

- VAG 1551/1552

- VAS 5051/5052/5053

- or VAG-COM + PC interface cable

To do this enter the following commands (in this case using a VAG 1552):-

01 - Engine Electronics (followed by the Q key)

08 - Read Measuring Block (followed by the Q key)

002 - Measuring Block 2 (followed by the Q key)

You should now look at the angle of the potentiometer (shown in the second column). It must read 0.00% when the throttle is fully closed (eg. at idle). This value should then increase as the throttle is gradually opened.

This adjustment procedure is particularly important. The following symptoms will be present if it is not adjusted correctly:-

Increased fuel consumption, erratic idling,
ECU does not recognise the idle position .
Accelerator end-stop screw
turned in too far !!
Engine cuts out or splutters on acceleration
from idle speed.
Accelerator end-stop screw
turned out too far !!

After you have adjusted the idle speed adjustment screw correctly, you should now use locktite or paint to prevent the thread from becoming loose.

The accelerator cable adjustment should now be checked which will require two people. You will need to watch the accelerator cam (shown in fig. 3) whilst your assistant sits inside the car and pushes the accelerator pedal down fully.

The gap between the accelerator cam (3) and it's full throttle end-stop (4) should be between 2mm to 3mm when the accelerator pedal is pushed down fully.

If this gap is incorrect, then it should be adjusted. Release the accelerator pedal and carry out the accelerator cable adjustment.

[Image] Key to fig. 3:-

3 = Accelerator Cam

4 = Full Throttle End-Stop

Fig.3 Adjustment at full throttle

The accelerator cable can be adjusted by undoing the 8mm bolt on the accelerator lever. You should now be able to move the accelerator cable to tighten it up. Pull it outwards to decrease the gap between the accelerator cam and the air intake's full throttle end-stop and do the opposite to increase that gap.

Once the accelerator cable has been adjusted, tighten up the 8mm bolt on the accelerator lever and repeat this adjustment procedure if necessary.

After you have adjusted the air intake unit correctly, the basic setting procedure must now be carried out. To do this make sure that the following conditions are satisfied:-

- No faults reported by the ECU

- Engine oil temperature at least 80°C

To carry out the basic setting procedure do the following (in this case with a VAG 1551/2):-

01 - Engine Electronics (followed by the Q key)

04 - Initiate Basic Setting (followed by the Q key)

001 - Block 1 (followed by the Q key)

Now wait for about 60 seconds for the ECU to learn the current setup (eg. throttle potentiometer position) and press the C or the -> key to exit the basic setting mode.

The car should now run properly.


Datum: 15.05.2005 22:01:32 Westeuropäische Sommerzeit

Ich hätte noch einen Tip in Bezug auf das "Sägen":
Mach 2 hatte trotz guter Grundeinstellung etc hin und wieder etwas gesägt. Das konnte man durch kurze Gasstösse zwar abstellen, war aber lästig. Es trat bei langsamer Gaswegnahme häufiger auf, daraus schloss ich dass evtl. der Gaszug leicht hängt und er deshalb den Leerlauf nicht sauber findet. Also habe ich nach deiner Technikseite das Drosselklappenspiel/abstand nochmal exakt eingestellt und den Seilzug am Gaspedal/ Eingang Tunnel und hinten Ausgang motorseitig mit "Breakfree CLP", einem Teflonhaltigen Superschmieröl geölt. Seither ist das Sägen nicht mehr aufgetreten.

Beste Grüsse aus Markt Schwaben ins Bibertal