Engine With One Knock Sensor
Requirements:Engine at normal operating temperature, 80°C (176°F).
All electrical consumers (A/C, rear window defroster, etc.).
Radiator fan must not be running while checking or adjusting.
No fuel pressure gauges connected to the fuel system.
Throttle valve in the proper idle position.
Throttle valve switch must be adjusted properly and working.
Exhaust system must be tight and free from leaks.
Oxygen sensor system in good working order.
NOTE: If the injection lines were loosened or replaced, run the engine up to at least 3000 RPM several times to clear the system of trapped air before making adjustments.
1. Initial setup
a. Remove the cap from the charcoal canister 'T' fitting (located near the fuel distributor).
b. Remove the breather hose from the elbow fitting at the valve cover. Plug the hose that is still connected to the valve cover.
c. Connect an exhaust gas analyzer to the exhaust manifold sampling port.
d. Connect a tach-dwell meter to the engine.
Connecting Ammeter To Idle Stabilizer Valve:
e. Disconnect the idle stabilizer valve harness plug, and install a test harness (VW 1315 A/2 or use set-up as shown in diagram) between the valve and the harness connector.
f. Connect a multimeter to the test harness, set to 2 Amp range.
2. Check Idle Speed
a. Start the engine and let it idle.
b. Idle speed should be;
Manual Trans. .......... 800 +/- 50 RPM
Automatic Trans. ...... 720 +/- 50 RPM
c. If the idle speed is not within specification, adjust the speed by turning the throttle bypass screw in the throttle housing.
d. Disconnect the green wire from terminal 1 of the ignition coil junction block (located on the ignition coil) to activate the idle stabilizer preset value.
e. Idle valve current reading should be 430 +/- 20 mA.
f. Reconnect the green wire to the ignition coil terminal block.
g. Idle valve current should be 430 +/- 20 mA and fluctuating, and the idle speed should remain within specifications.
3. Check the CO
a. Connect dwell meter to the test connector located near the fuel distributor.
b. Start the engine and allow it to idle.
The oxygen sensor dwell should be 35~-55~ (25 - 65%) and fluctuating.
The CO should be 0.3 - 1.2% (with oxygen sensor connected).
NOTE: If the CO is above 1.2%, and the dwell is between 35~ and 55~ (25% and 65%), check the following:
Ignition system (check the primary and secondary systems).
Exhaust system (look for leaks, and repair as necessary).
Fuel distributor (check for sticking control plunger, unequal injector volumes, etc.).
4. Adjust the CO
a. Switch the engine OFF.
b. Remove the intake air boot from the air flow sensor.
c. Drill a 3 mm (3/32 in.) hole in the concealment plug (located on the air flow sensor housing, between the fuel distributor and the air boot). Clean away any metal shavings, then extract the plug with a sheet metal screw and a pair of pliers.
d. Re-install the air boot.
e. Start the engine and allow it to idle.
f. Using a 3 mm allen wrench, adjust the duty cycle using the CO adjusting screw.
g. Turn the adjusting screw to change the dwell. The dwell should be between 35~ and 55~ (25% and 65%) and fluctuating.
Clockwise (richer) to decrease the dwell.
Counter-clockwise (leaner) to increase the dwell.
CAUTION: Do not push the adjustment wrench downward while adjusting. This will cause the engine to run lean and possibly backfire, causing damage to the air flow meter. Do not accelerate the engine with the adjustment tool in place, as it will bind in the adjustment hole, possibly damaging the air flow meter, the adjustment tool, or both.
h. Re-check the idle speed. The idle speed should be:
Manual Trans. 800 +/- 50 RPM
Automatic Trans. 720 +/- 50 RPM
i. Adjust idle speed if necessary.
NOTE: After adjustments are completed, re-connect the crankcase breather hoses. If the idle control current and the CO change, this is not due to improper adjustment, but rather to oil contamination. If the car is used only for short trips, fuel vapors can accumulate in the oil and dilute it. A long distance drive will return the oil to normal again. If a long drive is not possible, an oil change will cure the problem temporarily.