Engine Controls - Adjustments: Other Geo Prizm II

ENGINE MECHANICAL

Note. Unless otherwise indicated, references to Prizm include Prizm LSi.

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

VALVE CLEARANCE SPECIFICATIONS

1. Disconnect negative battery cable. Remove valve cover and gaskets. Rotate crankshaft until No. 1 cylinder is at TDC of compression stroke. Ensure timing mark on crankshaft pulley aligns with zero mark on timing belt cover.
2. Valves on No. 1 cylinder should have clearance and be closed. If both valves on No. 1 cylinder are not closed, rotate crankshaft one revolution (360 degrees).
3. Using feeler gauge, measure and record clearance between camshaft lobe and adjuster shim on intake valves of cylinders No. 1 and 2, and exhaust valves of cylinders No. 1 and 3. Adjust valve clearance if not within specification. See VALVE CLEARANCE SPECIFICATIONS table.
4. Rotate crankshaft one revolution (360 degrees). Check clearance on intake valves of cylinders No. 3 and 4, and exhaust valves of cylinders No. 2 and 4. Adjust valve clearance if not within specification. See VALVE CLEARANCE SPECIFICATIONS table.
5. To adjust valve clearance, rotate crankshaft until camshaft lobe is pointing upward, away from adjuster shim. Install Spring Compressor (J-39871-1) between camshaft and adjuster shim to push lifter downward. (Scheme 3)
6. Insert Lifter Detainer (J-39871-2) between camshaft and lifter. Ensure bottom edge of lifter detainer is positioned on lifter, not on adjuster shim. (Scheme 3) This will hold lifter away from camshaft.
7. Remove spring compressor. Using small screwdriver and magnet, remove adjuster shim. Replacement adjuster shim thickness can be determined by using adjuster shim charts. (Scheme 4)and (Scheme 5). Adjuster shim thickness can also be determined by using following formula: N = T + A N = Thickness of adjuster shim required. T = Thickness of adjuster shim removed. A = Measured clearance minus valve clearance specification.
8. To install NEW adjuster shim, depress valve spring using spring compressor. Install adjuster shim. Remove lifter detainer and spring compressor.
9. Ensure valve clearance is within specification. To install remaining components, reverse removal procedure.

Scheme 3

Scheme 4

Scheme 5

IGNITION TIMING

1. Warm engine to normal operating temperature. Turn engine off. Remove cover from Data Link Connector (DLC) located on left strut tower. Connect a tachometer to battery and terminal No. 19/IG (Black wire) of DLC. (Scheme 6) CAUTION: DO NOT ground terminal No. 19/IG in Data Link Connector (DLC). Grounding this terminal could result in ignitor or ignition coil damage.
2. Start engine. Ensure all accessories are off. With transaxle in Neutral, ensure idle speed is 650-750 RPM. If idle speed is not as specified, see IDLE SPEED under IDLE SPEED & MIXTURE.
3. Turn engine off. Connect timing light to No. 1 spark plug wire. Install jumper wire between terminals No. 3/E1 (Brown wire) and No. 8/TE1 (Blue/White wire) of DLC. (Scheme 6)
4. Start engine and check timing mark alignment on crankshaft pulley with timing marks on timing belt cover. Notch on crankshaft pulley should line up at 10 degrees BTDC on timing indicator.
5. If adjustment is required, loosen distributor hold-down bolts and rotate distributor until a 10-degree BTDC reading is obtained. Tighten distributor hold-down bolts to 15 ft. lbs. (20 N.m). Recheck ignition timing.
6. Turn engine off. Remove jumper wire from DLC. Recheck timing. Ignition timing should be varying between 5 degrees and 15 degrees BTDC. Remove timing light.

Scheme 6

IDLE SPEED & MIXTURE

Note. Air/fuel mixture is controlled by the Engine Control Module (ECM)/Powertrain Control Module (PCM) and is not adjustable.

IDLE SPEED

Idle speed adjustment is controlled by the Engine Control Module (ECM)/Powertrain Control Module (PCM). ECM/PCM controls idle speed with the Idle Air Control (IAC) valve. No adjustment is required. Check IAC valve as necessary.

California Only

1. Start engine and warm to normal operating temperature. Connect tachometer to battery and terminal No. 19/IG (Black wire) of data link connector. (Scheme 6)
2. Disconnect throttle opener vacuum hose from throttle opener, and plug hose. Maintain engine speed at 2500 RPM. Release throttle lever, and ensure throttle opener is set with engine speed at 1300-1500 RPM and radiator fan motor off. If throttle opener does not set, replace throttle opener.
3. If throttle opener setting speed requires adjustment, turn adjusting screw clockwise to increase engine speed or counterclockwise to decrease engine speed. (Scheme 7) Reconnect throttle opener vacuum hose to throttle opener and disconnect tachometer.

Scheme 7