Adjusting the Air/Fuel Mixture

NOTE: a. Refer to NOTES CONCERNING THE AIR/FUEL MIXTURE and CHECKING THE AIR/FUEL MIXTURE ADJUSTMENT for tester connection locations and procedures prior to adjusting the idle air/fuel mixture.
b. Adjustment procedure will require the use of on/off ratio tester (Bosch KDJE-P 600) or equivalent.
c. Adjustments are to be performed after the engine has reached normal operating temperature.
d. All accessories must be switched off.
e. Engine must be in good mechanical working order and be free from electrical misfires.
f. If after completing the adjustment procedures the correct On/Off Ratio can not be obtained refer to technical service bulletin #07318 in TECHNICAL SERVICE BULLETINS. Information concerning the possibility of internal fuel leakage within the CIS-E fuel distributor may lead to the remedy for the problem.

Fig. 70 Adjustment Tower Location:

1. Remove the air cleaner and drill a hole approximately 6 - 8 mm (15/64-5/16 in.) deep with a 2.5 mm (3/32 in.) twist drill in each of the break away bolts on the adjustment tower.

CAUTION: Do Not Drill Through The Bolts As The Metal Chips May Cause Engine Damage. Thoroughly Remove The Metal Chips With A Cleaning Rag.

2. Unscrew the break away bolts with a left hand twist drill or a screw extractor and remove the adjustment tower.
3. Install a new adjustment tower kit.
4. Reinstall the air cleaner and start the engine.

Fig. 40 Fuel Mixture Adjustment Location:

5. Push the screwdriver through the recess in the top section of the air filter housing and onto the adjusting device.
6. Push the adjusting device down with the screwdriver against the spring force, and turn it slightly until the hex head engages in the air/fuel mixture adjusting screw.

^ Turn the air/fuel mixture adjusting screw counterclockwise for a leaner air/fuel mixture. The on/off ratio will increase.
^ Turn the air/fuel mixture adjusting screw clockwise for a richer air/fuel mixture. The on/off ratio will decrease.

7. After each adjustment snap the throttle slightly, then check for the variation between 2500 RPM and idle speed with the on/off ratio tester. The difference between the two readings should not vary by more than +10. Adjust as necessary.
8. Switch off the engine.
9. Remove the air filter.

Fig. 71 Tamper Proof Lock:

10. Knock in the steel tamper proof lock with an appropriate tool so that the lock is flush with, or deeper than, the bottom edge of the taper of the adjusting tower.
11. Reconnect the purge line to the purge valve.
12. Reinstall the air filter.
13. Start the engine, turn on accessories, and place the transmission selector in drive.

^ The engine should run smoothly at idle.