Engine Controls - Adjustments Geo Prizm pre-I

IDENTIFICATION

MODEL IDENTIFICATION

ENGINE COMPRESSION

1. Warm engine to normal operating temperature. Ensure battery is fully charged, remove spark plugs, block throttle wide open and disconnect ignition coil primary connector.
2. Disconnect cold start valve, distributor and fuel injector connectors.
3. Put transmission in Neutral (M/T) or Park (A/T). Attach compression gauge and crank engine until maximum compression is reached at each cylinder and record pressure. See COMPRESSION SPECIFICATIONS table.

COMPRESSION SPECIFICATIONS

Scheme 1

VALVE CLEARANCE

1. Remove negative battery cable and valve cover. Rotate engine until zero degree mark on timing belt cover is aligned with timing mark groove on crankshaft pulley. Ensure cylinder No. 1 is at TDC by removing distributor cap and ensuring rotor is pointed at No. 1 spark plug wire terminal. If rotor does not point to No. 1 terminal, rotate crankshaft one revolution (360 degrees). (Scheme 1)
2. Check intake valve clearances of cylinders No. 1 and 2, and exhaust valve clearances of cylinders No. 1 and 3. Record clearance measurements of valves that are not within specification. See VALVE CLEARANCE SPECIFICATIONS table. Turn crankshaft one complete revolution (360 degrees). Check intake valve clearances of cylinders No. 3 and 4, and exhaust valve clearances of cylinders No. 2 and 4. Record clearance measurements of valves that are not within specification.
3. To adjust clearance, rotate crankshaft until cam lobe of appropriate valve is 180 degrees away from lifter adjusting shim. Use Lifter Compressor (J-37141-1) to push lifter down. Insert Lifter Detainer (J-37141-2A) between camshaft and lifter. (Scheme 2)
4. Remove lifter compressor and lifter adjusting shim using screwdriver and magnet. Calculate required lifter adjusting shim thickness using Shim Thickness Selection Charts. (Scheme 10)and (Scheme 11) or use following formula: N = T + A N = Thickness of shim required. T = Thickness of shim removed. A = Valve clearance measured minus valve clearance specification.
5. Replace removed lifter adjusting shim with one allows the required valve clearance. Repeat procedure as necessary.

Scheme 2

VALVE CLEARANCE SPECIFICATIONS

BASE TIMING

1. Inspect timing mark indicator and crankshaft pulley notch. (Scheme 1) Clean timing marks if necessary. Remove diagnostic connector cover, located on left strut tower. Connect tachometer to specified terminal of diagnostic connector. (Scheme 3)
2. Start and warm engine to normal operating temperature. Ensure idle speed is 700 RPM. Idle speed adjusting screw is located behind rubber plug on top left rear of intake plenum chamber, slightly forward of throttle position sensor. (Scheme 8) Turn off engine and all accessories. Attach timing light to No. 1 spark plug wire.
3. Connect jumper wire between diagnostic connector terminals "E1" and "T". (Scheme 3) Start engine and aim timing light at crankshaft pulley. If timing is not within specification on underhood emissions label or in IGNITION TIMING SPECIFICATIONS table, loosen distributor flange hold-down bolts and rotate distributor to obtain correct ignition timing.
4. Tighten distributor flange hold-down bolts to 15 ft. lbs. (20 N.m) and recheck timing. Remove jumper wire from diagnostic connector and install cover.
5. On all models except GSi, unplug Idle Speed Control (ISC) valve connector (mounted on front of intake plenum chamber) and recheck timing. (Scheme 4) Ignition timing should be 10 degrees BTDC. If timing is not 10 degrees BTDC, check for vacuum hose leak or ISC malfunction.
6. Reconnect ISC connector. Turn engine off. Remove timing light and tachometer. Install diagnostic connector cap.

Scheme 3

Scheme 4

IGNITION TIMING SPECIFICATIONS (Degrees BTDC @ RPM)

Ignition Timing Advance

Ignition timing advance curve is controlled by the Electronic Control Module (ECM). Proper pick-up coil air gap is necessary.

PICK-UP COIL AIR GAP (1)

IDLE MIXTURE

Note. Mixture is ECM controlled and nonadjustable on fuel-injected models.

FAST IDLE SPEED (ENGINE COLD)

Note. Cold start/fast idle speed is not adjustable on fuel-injected models. Air valve operation supplies by-pass air for cold starts.

Scheme 5

Scheme 6

1. Ensure air cleaner and all electrical connections and emission hoses are properly installed. Warm engine to normal operating temperature. Turn engine off. Ensure all accessories are off.
2. Remove cover from diagnostic cover, located on left strut tower. Connect tachometer to specified terminal of diagnostic connector and to the battery. (Scheme 4) CAUTION: DO NOT ground tachometer terminal in diagnostic connector, as grounding terminal could result in ignitor or ignition coil damage.
3. Install jumper wire between terminals E1 and "T" or TE1 of diagnostic connector. (Scheme 4) Start engine and note idle speed. Idle speed should be within specification. See IDLE SPEED SPECIFICATIONS table.
4. If idle speed requires adjustment, remove plug and rotate idle speed adjusting screw to obtain correct idle speed. (Scheme 5)and (Scheme 6).
5. On A/C equipped models, turn A/C on low speed. With A/C operating, idle speed should be within specification. See A/C IDLE SPEED SPECIFICATIONS table.
6. If idle speed requires adjustment, rotate adjustment screw on air conditioner idle-up Vacuum Switching Valve (VSV) to obtain correct idle speed. Idle-up VSV is located in right rear corner of engine compartment, near end of intake manifold on Prizm or left rear corner of engine compartment, near mass airflow sensor on Prizm GSi.
7. On all models, turn engine off and remove tachometer. Remove jumper wire from diagnostic connector and install cover on Prizm models.

IDLE SPEED SPECIFICATIONS (1)

A/C IDLE SPEED SPECIFICATIONS

Scheme 7

1. Ensure idle speed is within specification. See IDLE SPEED under IDLE SPEED & MIXTURE. With engine running, remove cap, filter and separator from dashpot on side of throttle body. (Scheme 7)
2. Maintain engine speed at 3500 RPM (Prizm) or 2500 RPM (Prizm GSi) and plug VTV hole inside dashpot. (Scheme 7) Release throttle and ensure engine speed is 1500 RPM (Prizm) or 1800 RPM (Prizm GSi).
3. If engine speed is not correct, rotate idle stop screw on throttle shaft until correct engine speed is obtained. With dashpot RPM adjusted, remove plug from VTV hole.
4. Ensure engine speed returns to correct idle speed in approximately one second. Reinstall dashpot components.

Prizm (4A-FE VIN 6)

1. Unplug throttle switch connector and loosen switch screws. Insert.028" (.70 mm) feeler gauge between throttle lever and stop screw. Using DVOM, check for continuity between switch terminals "E2" and "IDL." (Scheme 8)
2. Insert.032" (.80 mm) feeler gauge and ensure continuity does not exist between switch terminals. Adjust switch as necessary to achieve these results. Hold throttle switch and tighten screws. Recheck adjustment and reconnect throttle switch connector.

THROTTLE SWITCH RESISTANCE

Scheme 8

THROTTLE POSITION SENSOR (TPS)

Note. DO NOT use throttle stop screw to perform throttle position sensor adjustment on Metro with automatic transmission.

Prizm GSi (4A-GE)

1. Unplug TPS connector and loosen TPS attaching screws. Place.014" (.35 mm) feeler gauge between throttle lever and stop screw. (Scheme 9) Using DVOM, check for continuity between terminals "E2" (Brown wire) and "IDL" (Blue wire).
2. Place.032" (.80 mm) feeler gauge between throttle lever and stop screw. Connect ohmmeter between terminals "E2" and "IDL". TPS should have NO continuity with throttle in idle position.
3. If resistance values are incorrect, loosen TPS attaching screws and rotate TPS until correct readings can be obtained. Hold TPS in this position, tighten attaching screws to 30 INCH lbs. (3.4 N.m) and repeat inspection procedure to verify correct operation. See THROTTLE POSITION SENSOR (TPS) RESISTANCE table. If TPS cannot be adjusted to obtain the correct values, replace TPS.

Scheme 9

THROTTLE POSITION SENSOR (TPS) RESISTANCE

Scheme 10

Scheme 11