Engine Controls - Basic Diagnostic Procedures - 2.2L: Other Pontiac Sunfire I

Compression

The results of a compression test will fall into the following categories

1. Normal Compression builds up quickly and evenly to specified compression on each cylinder.
2. Piston Rings Compression is low on the first stroke, tends to build up on following strokes, but does not reach normal. Compression improves considerably with the addition of oil.
3. Valves Compression is low on the first stroke, does not tend to build up on the following strokes, and does not improve much with the addition of oil. Use approximately three squirts from a plunger-type oiler.

1. Conduct the following steps in order to check cylinder compression: Engine should be at room temperature. Disconnect wiring from the ignition module. Remove the spark plugs. Throttle body valve should be wide open. Battery should be at or near full charge.
2. For each cylinder, crank engine through four compression strokes.
3. The lowest reading cylinder should not be less than 70 percent of the highest.
4. No cylinder reading should be less than 100 psi (689 kPa).

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. See RESTRICTED EXHAUST under SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.

FUEL SYSTEMS

Note. For fuel pump circuit testing, see appropriate diagnostic procedure under NO-START DIAGNOSIS .

Manufacturer does not provide testing procedures for many individual systems and components. For fuel system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.

FUEL SYSTEM PRESSURE RELEASE (GASOLINE)

1. Disconnect the negative battery cable.
2. Connect Fuel Pressure Gauge (J 34730-1A), or equivalent, to the fuel pressure connection, located on the fuel rail. see scheme 1
3. Place the bleed hose into an approved container and open the valve to bleed the system pressure. The fuel connections are now safe for servicing.
4. Open the valve to bleed the system pressure. The fuel connections are now safe for servicing.
5. Disconnect the fuel pressure gauge from the fuel pressure connection.

FUEL SYSTEM PRESSURE RELEASE (CNG)

Note. If High Pressure Lock-Off (HPL) is replaced, or tank is to be cleaned, replaced or shipped, also perform FUEL TANK VENTING (CNG) under FUEL SYSTEMS (CNG) in REMOVAL & INSTALLATION - CAVALIER & SUNFIRE article.

1. Using a scan tool communicate with the PCM. If communication cannot be established and the «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS (ALTERNATIVE FUELS)»(ref-154639-S18635029522003051900000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article, has already been performed proceed to step 9.
2. Store the DTC Information using the scan tool.
3. Clear the DTC Information using the scan tool.
4. Turn ignition switch to OFF position.
5. Start and idle the engine. If the engine fails to operate on CNG or start at all, go to step 9.
6. Ensure that the engine is operating on CNG by observing if the Fuel Indicator Light (FIL) is OFF, or the AFO Enable scan tool display indicates the engine is operating on alternative fuel.
7. Using a scan tool, select the HIGH PRESSURE LOCK-OFF (HPL) solenoid special function.
8. While the engine is operating on CNG command the HPL solenoid OFF and observe the fuel tank pressure sensor data parameter. The fuel tank pressure should slowly decrease. If the fuel pressure fails to decrease proceed to next step. When the engine stalls or a switch-over to gasoline is observed, perform the following: Turn ignition switch to OFF position. NOTE: Turning the ignition ON with the AF Lock-off fuse removed may set a DTC. Clear DTC Information after repairs are complete. Remove the ALT. FUELS LOCK-OFF 10-amp fuse in order to disable the CNG fuel system. A small amount of CNG will remain in the fuel lines and components. Slowly open the fittings in order to release any remaining pressure when disconnecting a fuel line. Fuel Pressure Relief for the CNG system is now complete. Proceed to step 16.
9. Close the manual lock-down screw located on the end of the High Pressure Lock-Off (HPL) solenoid. The manual shut-off fitting is closed by rotating the Allen screw clockwise until fully seated. (Scheme 76)
10. Turn ignition switch to OFF position.
11. Disconnect the negative battery cable.
12. Slowly loosen the fuel line fitting at the Low Pressure Lock-Off (LPL) solenoid elbow several turns. (Scheme 77)
13. Fuel Pressure Relief for the CNG system is complete when the fuel line can be pulled away from the "O" ring face seal and fuel does not vent.
14. Replace the "O" ring face seals at all fittings that were disconnected or loosened.
15. After all necessary repairs are complete perform the following: Tighten any loosened fittings to specification. See «TORQUE SPECIFICATIONS»(ref-153402-S15109679952003040400000) in REMOVAL & INSTALLATION - CAVALIER & SUNFIRE article. Open the manual lock-down screw located on the HPL manual shut-off fitting by rotating the Allen screw counter-clockwise until fully seated on any vehicle that does not require venting of the CNG fuel tanks.
16. If the service necessary for the vehicle requires the CNG fuel tanks to be relieved of all internal pressure, go to «FUEL TANK VENTING (CNG)»(ref-153402-S00524229582003040400000) under FUEL SYSTEMS (CNG) in REMOVAL & INSTALLATION - 2.2L CAVALIER & SUNFIRE article.

Scheme 76

Scheme 77

High Pressure Regulator Stage

When the PCM commands the HPL open fuel begins to flow through the High Pressure Regulator (HPR). The HPR reduces fuel pressure to between 110-210 psi (758-1448 kPa).

Low Pressure Regulator Stage

With a pressure between 110-210 psi (758-1448 kPa) the fuel exiting the HPR flows through the intermediate fuel line to the Low Pressure Lock-Off (LPL) solenoid. The LPL is controlled by the PCM. Fuel flows out of the LPL and into the Low Pressure Regulator (LPR). The LPR reduces fuel pressure to between 43-46 psi (246-317 kPa). Fuel flows out of the LPR and into the fuel rails.

IGNITION SYSTEMS

Note. For circuit identification, see WIRING DIAGRAMS .

Manufacturer does not provide testing procedures for many individual systems and components. For ignition system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Camshaft Position Sensor

A malfunction in Camshaft Position (CMP) sensor can set a DTC. For testing procedures and specifications, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.

Crankshaft Position Sensor

A malfunction in Crankshaft Position (CKP) sensor can set a DTC. For testing procedures and specifications, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.

Crankshaft Position (CKP) Sensor Output Signal

Set DVOM on 2-volt AC scale. Connect DVOM leads to CKP sensor located on side of engine block. Crank engine and observe voltmeter reading. CKP sensor should generate a voltage signal of about 2 volts.

Tach Pulse (RPM) Signal

Connect scan tool to DLC. RPM should be indicated on scan tool when engine is cranked or running. Tach pulse (RPM reference) will be indicated as a voltage signal when a DVOM (with a minimum 10-megohm input impedance connected to ground) is used to backprobe RPM high reference circuit. If tach pulse signal is not present, engine will not run.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For specifications and adjustments, see appropriate SERVICE & ADJUSTMENT SPECIFICATIONS and ON-VEHICLE ADJUSTMENTS articles.

ALERO

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

CAVALIER

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

GRAND AM

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SUNFIRE

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.