Air Flow Sensor, Checking and Adjusting

Air Flow Sensor, Checking and Adjusting

WARNING: Fire Hazard! Do not smoke or have anything in area that can ignite fuel.

Sensor plate lever and control plunger, checking

- pull injectors out of inserts and place in openings of VAG 1348/2B fuel analyzer
- operate either starter or remote control VAG 1348/3A for approx. 10 seconds





- check quality of sensor plate lever movement by lifting sensor plate bolt using magnet
- sensor plate lever must exhibit same resistance over entire travel

- pull sensor plate upward with a quick movement using a magnet on the sensor plate bolt
- no change in lever resistance should be felt

If YES

- replace air flow sensor assembly

If sensor plate lever is difficult to move upward but moves downward easily

- replace fuel distributor
- control plunger is hanging up





Sensor plate rest position, checking

- upper edge of sensor plate must be dimension "a" below cone edge of venturi
- a = 1.9 + 1.1 mm

Sensor plate rest position, adjusting

- remove upper section of air filter housing and remove air filter element





- adjust rest position clearance (dimension "a") using adjustment nut (arrow)
- a = 1.9 + 1.1 mm

CAUTION: Do not bend leaf spring while performing adjustment.

Sensor plate free play, checking

Requirements
- sensor plate rest position OK
- CO adjustment OK





NOTE: Free play is the clearance between the control plunger and sensor plate lever (right arrow), measured on the side of the sensor plate closest to the fuel distributor (left arrow).

- operate starter or remote control VAG 1348/3A for approx. 10 seconds

- lift sensor plate slightly until resistance is felt
- free play: 0.5 mm minimum
3.0 mm maximum (up to edge of venturi)

If free play NOT OK
- adjust free play on fuel distributor via control plunger

Sensor plate free play, adjusting at fuel distributor

Requirement
- CO adjustment OK





- adjust sensor plate free play using wrench VW 674/2 on control plunger stop screw

- distance "a" = 0.6 mm between stop screw and collar of hex hut

- 1/4 turn = approx. 1.3 mm of play at sensor plate

- turning in = increases free play

- turning out = decreases free play

After free play adjustment is completed

- re-check free play adjustment, if necessary adjust CO content via control current adjustment





Sensor plate lever, basic adjustment

NOTE: The basic adjustment should only be performed if the fuel distributor or air flow sensor have been replaced.

- measure distance between the air flow sensor housing opening (for the fuel distributor) and the sensor plate lever roller, if necessary adjust using CO adjusting screw
- must be 21.3 ± 0.1 mm*

* After adjusting CO content to specifications (via control current), this dimension no longer applies.





Control plunger, removing

- mark position of stop screw by scribing
- measure and record distance "a" between stop screw and hex nut collar

- remove stop screw using VW 674/2 wrench

Control plunger, Installing

- wash control plunger with clean gasoline before installing
- inspect stop screw sealing ring for damage, replace if necessary
- install with smaller diameter 0 of sealing ring towards control plunger





- insert stop screw using VW 674/2 wrench until previously recorded dimension "a" is obtained
- check sensor plate rest position and free play, adjust if necessary

NOTE: Mechanically cleaning the control plunger is not permitted. If the piston shows heavy scoring and/or does not move easily after washing with clean gasoline, the complete fuel distributor must be replaced.