Compression, Checking

WARNING: This page is about a different variant/trim than selected.

Special tools and workshop equipment required

Spark Plug Removal Tool:3122 B

Fig 1: Identifying Spark Plug Removal Tool 3122B
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Trim Removal Wedge:3409

Fig 2: Identifying Trim Removal Wedge
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Compression Tester Kit:V.A.G 1763

Fig 3: Compression Tester Kit VAG 1763
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Adapter:V.A.G 1763/13 , not illustrated
Engine Bung Set:VAS 6122

Fig 4: Engine Bung Set
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Test Sequence

Engine oil temperature at least 30 °C.
Battery voltage at least 12.7 V.

All except Audi Q7/Q8:

-- Remove the engine cover. Refer to ENGINE COVER, REMOVING AND INSTALLING .

Audi Q7/Q8:

Refer to the appropriate Service Information.

Audi A6/A7 with High-Voltage System:

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-- Free up the wiring harness.

-- Lift the clamp -3-, remove and free up the coolant hose.

-- Disconnect the connector -5- for the Engine Coolant Level Sensor -G32-.

-- Remove the bolt -4-, and push the coolant expansion tank to the side.

Continuation for all Vehicles with High-Voltage System:

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-- Disconnect the connector -2- for the Charge Air Pressure Sensor -G31-.

-- Loosen the screw-type clamp -1- and remove the air duct pipe from the Throttle Valve Control Module -GX3- (example illustration).

-- Seal off any open lines and connections with plugs that are thoroughly cleaned from the Engine Bung Set:VAS 6122 .

-- Disconnect the connection -1- for Throttle Valve Control Module -GX3-.

Fig 5: Identifying Throttle Valve Control Module Electrical Connector And Bolts

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-- Open the throttle valve by hand and lock it in open position using the Trim Removal Wedge:3409 or a wooden wedge -arrow-.

Fig 6: Locating Throttle Valve

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-- Appropriately secure the trim removal or wooden wedge using a thread.

CAUTION:

Risk of destroying the engine due to accidentally sucked in foreign objects while the throttle valve control module is open or removed.

- Make sure that no foreign objects are located in the work area and that the trim removal or wooden wedge is secured.

-- Connect the Vehicle Diagnostic Tester and switch on the ignition.

-- Select the Diagnostic mode and start the diagnosis.

-- Select the Test plan tab.

-- Select the Select individual test button and select the following tree structure consecutively:

Diagnostic-capable systems
0001 - Engine electronics J623
0001 - Engine electronics, functions
0001 - Activate the service mode

Continuation for All Vehicles:

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-- Disconnect the fuel injector connector -arrow-.

-- Remove the ignition coils. Refer to IGNITION COIL, REMOVING AND INSTALLING .

-- Remove the spark plugs using the Spark Plug Removal Tool:3122 B .

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-- Install the Adapter:V.A.G 1763/13 as shown in the respective spark plug hole and connect the Compression Tester Kit:V.A.G 1763 .

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-- Check the compression using the Compression Tester Kit:V.A.G 1763 . Refer to the appropriate Operating Information.

-- Have a second technician operate the starter until the tester stops displaying a pressure increase.

-- Repeat the procedure on each cylinder.

Compression pressure	bar pressure
Compression pressure	Performance class 2	Performance class 3
New	10.0 to 14.0	9.0 to 13.0
Wear limit	7.0	6.0
Maximum difference between cylinders	3.0	3.0

TIP:

If the test with the Compression Tester Kit:V.A.G 1763 does not lead to a clear result there are two additional tests.

In addition to the compression test a pressure test can be performed with the Pressure-Loss Tester:VAS 522 001 . The procedure for this is described in the operating instructions for the Pressure-Loss Tester:VAS 522 001 .
As an additional test the CO2 content in the coolant expansion tank can be measured. A raised CO2 content in the cooling system indicates a leak between the combustion chamber and the cooling system. The CO2 content can be determined using the CO2 Coolant Tester:VAS 531 009 . The procedure for this is described in the operating instructions of the CO2 Coolant Tester:VAS 531 009 .

Assembling

-- Install the spark plugs. Refer to OVERVIEW - IGNITION SYSTEM .

-- Install the ignition coils. Refer to IGNITION COIL, REMOVING AND INSTALLING .

Refer to the appropriate Service Information.

-- Install the engine cover. Refer to ENGINE COVER, REMOVING AND INSTALLING .

-- Delete the DTC memory entries in the engine control module that have occurred during the test using the Vehicle Diagnostic Tester.

Tightening Specifications

Refer to the appropriate Service Information.