Getting Correct Co Level Porsche 928

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It is recommended to use the test connection in area of air cleaner housing, if there is suspicion of erratic engine running or when troubleshooting.

CO testing pipe for cylinders 1 - 4 is on righthand side, or lefthand side for cylinders 5 - 8.

Sensor Disconect

2. Disconnect oxygen sensor plug and connect CO tester according to supplier's instructions.

3.Install Special Tool US 4492 on CO testing pipe.

4. Check CO. If CO level deviates from specified value, correct the adjustment on air volume sensor. Use Special Tool 9230.

ADJUSTING IDLE (32 VALVE ENGINE)

Note

Engine in perfect mechanical condition. Electric equipment switched off during adjustments. Adjustments made as quickly as possible to prevent heating up the intake ports and consequently causing wrong CO values.

1. Run engine to operating temperature (oil temperature 80 to 90° C). Use Special Tools 9122 + 9122/1 to check oil temperature: 15 to 30° C.

2. Disconnect oxygen sensor plug and connect CO tester according to supplier's instructions.

3.Install Special Tool US 4492 on CO testing pipe.

It is recommended to use the test connection in area of air cleaner housing, if there is suspicion of erratic engine running or when troubleshooting.

CO testing pipe for cylinders 1 - 4 is on righthand side, or lefthand side for cylinders 5 - 8.

CO adjusting value: 0.6 + 0.2 % Turned clockwise - richer mixture

Turned anticlockwise - leaner mixture

If the CO level has to be corrected on the air volume sensor, remove plug in bore affording access to the idle speed CO adjusting screw after removal of the air volume sensor.

CO adjusting value: 0.6 + 0.2 % Turned clockwise - richer mixture

Turned anticlockwise - leaner mixture

If the CO level has to be corrected on the air volume sensor, remove plug in bore affording access to the idle speed CO adjusting screw after removal of the air volume sensor.

5. Connect oxygen sensor plug and insert plug in CO testing pipe after finishing adjustments.

6. Connect separate tachometer to supplier's instructions.

Idle speed adjusting value: 680 + 20 rpm.

7. Check and adjust idle speed.

This requires stopping the idle speed charging control.

a) Connect test jacks B and C with a piece of locally made wire. This stops idle speed charging control.

b) Check and adjust speed with, for example, VAG Tester 1367.

8. Turn control screw (bypass) on throttle housing with a standard screwdriver, e.g. Hazet 428 - 7, until the specified speed of 680 + 20 rpm.

9. Restore idle speed charging control after finishing adjustments (remove locally made wire on test jacks).

10. Recheck adjusted values.

CORRECTING CO ADJUSTMENT ON AIR VOLUME SENSOR (32 VALVE ENGINE)

Note

If CO level deviates from the specified value, remove plug in bore affording access to the CO adjusting screw after removal of the air sensor.

Removing

1. Remove air sensor.

2. Drill hole in plug with a 2 mm dia. drill (up to stop on steel insert).

3. Pull out plug with a lefthand spiral drill (size no. 2).

3. Install a new plug in bore affording access to CO adjusting screw after finishing adjustments. Press in plug flush.

Note

Drilled plugs must never be reused.

Installing 1. Install air sensor.

2. Adjust CO and engine idle speed. Turn CO adjusting screw accordingly with Special Tool 9230.

Turned clockwise - richer mixture Turned anticlockwise - leaner mixture

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Correcting CO Adjustment On Air Volume Sensor

FUEL PATH - LH-JETRONIC 928 S 85 MODELS ONWARD (32-VALVE ENGINES) ENGINE TYPE M28. 43/44/45/46

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