Compression, Checking

WARNING: This page is about a different car, the 2024 Audi Q5 and 2023 Audi Q5. However, it is still accessible from the selected car via links, so may be relevant.

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:

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 Operating Manual.

-- 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 .

-- 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