TERMINOLOGY
Due to federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The following table will help eliminate confusion when dealing with these components and systems. Only relevant components and systems whose names have changed from current General Motors Corp. terminology have been listed.
| Former Name Or Acronym | New Name Or Acronym |
|---|---|
| ALDL | Data Link Connector (DLC) |
| CHECK ENGINE Light | Malfunction Indicator Light (MIL) |
| CTS | Engine Coolant Temperature Sensor |
| Diagnostic Circuit Check | On-Board Diagnostic (OBD) System Check |
| ESC System | Knock Sensor (KS) System |
| EST System | Ignition Control (IC) System |
| MAT Sensor | Intake Air Temperature (IAT) Sensor |
| Park/Neutral (P/N) Switch | Park/Neutral Position (PNP) Switch |
| Port Fuel Injection | Multi Port Fuel Injection |
| Scan Data | Scan Tester (ST) Data |
| SERVICE ENGINE SOON Light | Malfunction Indicator Light (MIL) |
| Thermostatic Air Cleaner (TAC) | Air Cleaner (ACL) |
| Throttle Position Sensor (TPS) | Throttle Position (TP) Sensor |
| Throttle Position Switch | Closed Throttle Position (CTP) Switch |
| Throttle Position Switch | Wide Open Throttle (WOT) Switch |
| Viscous Converter Clutch (VCC) | Torque Converter Clutch (TCC) |
| (1) Text includes old and new terminology. This is a representative listing. | |
| (1) | Text includes old and new terminology. This is a representative listing. |
SAE TERMINOLOGY CHART (1)
Compression
Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. See engine analyzer manual for specific instructions. See COMPRESSION SPECIFICATIONS table.
| Application | Specification |
|---|---|
| Compression Ratio | 9.5:1 |
| Normal Compression Pressure | 199 psi (14.0 kg/cm 2 ) |
| Minimum Compression Pressure | 156 psi (11.0 kg/cm 2 ) |
| Maximum Variation Between Cylinders | 14 psi (1.0 kg/cm 2 ) |
COMPRESSION SPECIFICATIONS
Exhaust System Backpressure
Exhaust system can be checked using a vacuum or pressure gauge. If using a pressure gauge, remove O2 sensor or air injection check valve (if equipped). Connect a 1-10 psi pressure gauge. Operate engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.
If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restriction.
FUEL SYSTEM
| WARNING | Always relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. |
FUEL PRESSURE RELEASE
- Loosen fuel tank cap to release fuel tank pressure. Remove cover from main fuse box located in left front corner of engine compartment, behind battery. Remove coolant reservoir from bracket. Remove main fuse box retaining screws. From underneath main fuse box, release 2 locking tabs of fuel pump relay. (Scheme 10)
- Remove fuel pump relay from main fuse box. Disconnect electrical connector from fuel pump relay. Start engine. Idle engine until it dies. Crank engine for about 10 seconds to ensure residual fuel line pressure is released. Turn off ignition. Install fuel pump relay.
Scheme 10
FUEL PRESSURE
Note. For fuel pump specifications, see FUEL PUMP PERFORMANCE table.
Release fuel pressure. See FUEL PRESSURE RELEASE. Disconnect negative battery cable. Remove air cleaner assembly. Remove fuel inlet hose from throttle body. Install Fuel Pressure Gauge (J-34730-1) and Adapter (J-34730-75). (Scheme 11) Reconnect negative battery cable. Check fuel pressure. see scheme 10, see scheme 11 and see scheme 12. Release fuel pressure. Remove fuel pressure gauge.
Scheme 11
| Application | Pressure: psi (kg/cm 2 ) |
|---|---|
| Metro | (1) 23-30 (1.6-2.1) |
| (1) With ignition on and engine off. | |
| (1) | With ignition on and engine off. |
FUEL PUMP PERFORMANCE
IGNITION CHECKS
Note. For a no-start condition, see DIAGNOSTIC CHARTS .
SPARK
Crank engine, checking for a strong Blue spark at coil wire and each spark plug wire using Spark Tester (ST-125). If spark exists on some spark plugs, check for defective distributor cap and defective rotor. Check spark plug high tension wire resistance. Replace spark plug high tension wires if resistance exceeds specification. See the HIGH TENSION WIRE RESISTANCE table.
| Application | Ohms |
|---|---|
| All Models | (1) 3000-6500 |
| (1) Resistance for every 12" (305 mm) of wire. | |
| (1) | Resistance for every 12" (305 mm) of wire. |
HIGH TENSION WIRE RESISTANCE
IGNITION COIL POWER SOURCE
Turn ignition switch to ON position. Using voltmeter, check voltage between positive terminal of ignition coil (Black/White wire) and ground. If battery voltage does not exist, check for open circuit in Black/White wire between ignition coil and 20-amp ignition fuse in fuse block. Fuse block is located below left side of instrument panel.
IGNITION COIL RESISTANCE
- Disconnect negative battery cable. Remove protective cap from ignition coil. Disconnect coil high tension wire from ignition coil.
- Remove wires from positive and negative terminals (primary wires) of ignition coil. Using ohmmeter, check primary resistance between positive and negative wire terminals (primary terminals) of ignition coil.
- Check secondary resistance between ignition coil high tension wire terminal (secondary terminal) and primary positive terminal. Replace ignition coil if readings are not within specification. See «IGNITION COIL RESISTANCE»(ref-19470-S23169503692001010200000) table.
| Application | Primary | Secondary |
|---|---|---|
| Metro | 1.33-1.55 | 10,700-14,500 |
IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)
PICK-UP COIL/CRANK ANGLE SENSOR
Measure pick-up coil/crank angle sensor air gap. If gap is not .008-.016" (.20-.40 mm), adjust or replace distributor. Check pick-up coil/crank angle sensor resistance. See I - SYS/COMP TESTS article in this section.
Scheme 12
IDLE SPEED & IGNITION TIMING
Ensure idle speed and base ignition timing are set to specification. For adjustment procedures, see ADJUSTMENTS article in this section.
CHART A-3, ENGINE CRANKS BUT WILL NOT RUN
Before using this chart, ensure battery condition, engine cranking speed and fuel quantity are okay.
When ignition switch is in ON or START position, battery voltage is applied to ignition coil. If ignition coil's primary coil is being toggled to ground by ECM, a high voltage is induced in secondary windings of ignition coil and is applied through distributor to spark plugs.
Note. Test numbers refer to numbers on diagnostic chart.
- Checks if diagnostic trouble codes are stored in ECM memory.
- Checks for spark at ignition coil.
- Checks for spark at distributor.
- Checks for spark at spark plugs.
CHART A-5, FUEL INJECTION CKT CHECK (NO-START)
When fuel injector is energized by ECM, it will activate fuel injector plunger and pressurized fuel will be injected into throttle body. Fuel pump will operate as long as engine is cranking and ECM is receiving ignition reference pulses.
Note. Test numbers refer to numbers on diagnostic chart.
- Checks to see if ECM is controlling fuel injector signals.
- This checks fuel injector for correct resistance.
- This checks for voltage at fuel injector.
- This checks for an open or short to ground in Yellow/Black wire, a faulty ECM and a faulty fuel injector.
- This checks for an open or short to ground in Yellow wire, an open in White/Blue wire, and a faulty fuel injector resistor.
CHART A-7A, FUEL PUMP RELAY CHECK
With ignition on, ECM energizes fuel pump relay for 3 seconds, allowing for fuel pump operation. When fuel pump relay is de-energized, fuel pump stops operating. If engine is being cranked or is running, fuel pump will continue to operate as long as ECM is receiving ignition reference pulses. If ignition reference pulses are not detected, fuel pump will stop after 3 seconds.
Note. Test numbers refer to numbers on diagnostic chart.
- Checks fuel pump operation with ignition switch in ON position.
- Checks fuel pump relay switch for power.
- Checks for faulty ECM and improper fuel pressure.
- Checks fuel pump circuit.
- Checks for open in Pink wire from fuel pump relay to fuel pump.
- Checks for faulty fuel pump relay coil for power.
- Checks for faulty fuel pump or an open in Black wire (ground).
- Checks for faulty fuel pump relay.
- Checks for faulty ECM or an open in Pink/White wire from fuel pump relay to ECM.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, go to TESTS W/CODES article in this section. If no hard codes are found in self-diagnostics, go to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.