Idle Speed & Mixture: Notes

NOTE: Ignition timing and valve clearances must be correct and engine must be at normal operating temperature prior to adjusting idle speed and mixture.

Disconnect canister purge hose at check valve near intake manifold. Plug hose, then start engine and warm up for at least 5 minutes. Adjust idle speed with transmission in neutral.

Fig 1: Idle Mixture Test Connections
Courtesy of SUBARU OF AMERICA, INC.

NOTE: Idle mixture should not need adjustment unless carburetor has been removed and disassembled. Roll pin must be removed from in front of idle mixture screw before adjustments can be made.
Connect a dwell meter to Yellow/Red wire in Pink connector near right front shock tower. Set meter on 4 cylinder scale and observe needle movement with engine idling. See Fig 1.
Dwell meter needle should move up and down within a 30-40° range. If not moving, run engine at 2000-3000 RPM for at least 2 minutes, then recheck. After noting movement, move dwell meter lead to Yellow/Green wire in Pink connector and repeat check.
If dwell meter needle movement is not within specified range, adjust idle mixture screw until needle movement is between 27-36°. Repeat adjustment and check with both solenoid wires in Pink test connector. Recheck idle speed, then remove test equipment, reconnect purge hose and install roll pin.