Idle Mixture Adjustment

1. Connect either the BOSCH KDJE 7457 tester or equivalent to test wire no. 153 to read the OCR (Open Cycle Ratio).
2. Adjust idle speed to 800 RPM.
3. Read the OCR value on the meter. The reading should be equal to 62% - 68%. For dwell meter conversion use the following formula: dwell meter reading multiplied by 100 divided by degree scale of dwell meter. (for a 90° scale, use 90; for a 60° scale use 60).
4. If OCR reading is not within specs, adjust as follows:
a. Remove the DO NOT TAMPER plug.
b. Disconnect battery and remove connecting boot between throttle body and fuel metering distributor.
c. Remove air supply hose to air pump and PCV hose.
d. Taking care not to damage fuel hoses, disengage the 4 screws and separate the fuel metering distributor from the air cleaner housing.
e. Turn fuel distributor upside down and remove flow plate lower stop.

Fig. 7 Removing tamper resistant plug:

f. Drive out tamper resistant plug using 3 mm drift, Fig. 7.

Fig. 5 Idle Mixture Adjustment:

g. Adjust idle mixture, Fig. 5, to obtain a reading of 62% - 68% on the dwell meter.

NOTE: BEFORE EACH READING, REMOVE THE SPECIAL SCREWDRIVER FROM THE ADJUSTMENT SCREW.

h. Recheck idle speed. If it incorrect, perform the idle mixture adjustment again, starting with step 2.
i. The adjustment may be verified by connecting a HC-CO analyzer.
j. Install the pick up probe onto the front tap of the catalytic converter, the Teflon hose onto the probe, and the hose to the analyzer. The CO should be 0.3% - 1.3%.
k. Readjust if necessary, beginning with step 2.
l. Install a new DO NOT TAMPER plug .
m. Remove the pick up probe and reinstall the plug on the catalytic converter.