Nissan 240sx S13 Engine Performance Basic Diagnostic Procedures

Nissan 240sx S13



NOTE: Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition. The first step in diagnosing any driveability problem is verifying the vehicle operator's complaint with a test drive under the conditions the problem reportedly occurred. Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Compression
Check engine mechanical condition using a compression gauge, vacuum gauge or an engine analyzer. See engine analyzer manual for specific instructions.

4-CYLINDER COMPRESSION SPECIFICATIONS

• Normal Compression Pressure: 179 psi (12.6 kg/cm2)
• Minimum Compression Pressure: 151 psi (10.6 kg/cm2)
• Maximum Variation Between Cylinders: 14 psi (1.0 kg/cm2)

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 0-5 psi pressure gauge. Run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4-2 psi (.12-.14 kg/cm2 ), 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 a restriction.

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FUEL SYSTEM

FUEL PRESSURE

Begin basic diagnosis of fuel system by determining fuel system pressure. If fuel pump is inoperative, check fuel pump fuse.

WARNING: Always relieve fuel pressure before disconnecting any fuel injectionrelated component. DO NOT allow fuel to contact engine or electrical components. If connecting fuel pressure gauge to fuel system without using a "T" connector, DO NOT operate fuel pump for more than a few seconds. Operating fuel pump longer than a few seconds under this
condition can damage fuel pump.

1. To relieve fuel system pressure, remove fuel pump fuse. Start engine, and allow it to run until it stalls. Crank engine 2 or 3 more times to verify all pressure has dissipated.
2. Turn ignition off. Install fuel pump fuse or relay. Connect fuel gauge between fuel filter outlet and fuel tube using a "T" connector. Disconnect electrical connector at fuel pressure regulator control solenoid valve (if equipped).
3. Start engine. Check fuel line connections for leaks. Check fuel pressure with engine idling. Disconnect vacuum hose from pressure regulator. Recheck fuel pressure.
4. Compare fuel pressure readings on pressure gauge with specifications in FUEL PRESSURE table. Release fuel system pressure as described in step 1). Disconnect fuel pressure gauge. Reconnect fuel lines. Start engine and check for fuel leaks.

FUEL PRESSURE

• 240SX
  • At Idle W/O Vacuum psi (kg/cm2): 43 (3.0)
  • At Idle W/ Vacuum psi (kg/cm2): 34 (2.4)

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IGNITION CHECKS

DISTRIBUTOR IGNITION

To determine cause of no-spark condition, perform following tests in order given. Deviation from this procedure may cause false diagnosis and replacement of non-defective components.
Spark Check for spark at coil wire and each spark plug wire using spark tester. DO NOT crank engine continuously for more than 2 seconds. Inspect secondary coil wire for arcing while testing spark at plugs. Check electrical connections at Crankshaft Position (CKP) sensor, ignition coil and power transistor.

Ignition Coil Power Source
1. Disconnect ignition coil 2-pin connector. Turn ignition on. Check for voltage at specified wire terminal.
2. If voltage is present, go to POWER TRANSISTOR. If voltage is not present, check continuity of entire circuit between battery and ignition coil, including fuse link and ignition switch.

IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION

• 240SX - Wire Color: Light Green/Black

Ignition Coil Resistance
1. If ignition coil malfunction is suspected, carefully inspect external housing for burned spots indicating secondary circuit arcing to primary or ground circuits. Disconnect ignition coil primary 2-pin connector.
2. Using an ohmmeter, check resistance between primary connector terminals. Check resistance between secondary tower and positive terminal of coil primary connector. Positive terminal is identified by wire color in IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION table. If either resistance is not as specified, replace ignition coil.

4-CYLINDER IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)

• 240SX
  • Primary: 1.0
  • Secondary: 10,000

Crankshaft Position (CKP) Sensor
1. CKP sensor is located inside distributor. If a fault is present in CKP sensor, Code 11 may be set in ECM memory. If Code 11 is set, perform appropriate CODE 11 (CKP SENSOR).
2. To test CKP sensor, remove distributor. Leave wiring harness connected. Using a voltmeter, connect negative lead to ground and alternately connect positive lead to 1-degree signal terminal and 120/180- degree signal terminal. See Fig. 1 .
3. Measure voltages at both terminals while rotating distributor by hand. Voltage should fluctuate 0-5 volts. If either voltage signal does not fluctuate 0-5 volts, check harness for short or open circuit. If no problems are found, replace CKP sensor.

CKP SENSOR INPUT SIGNAL TERMINALS

• 240SX
  • 1-Degree Signal: Terminal No. 2
  • 120/180-Degree Signal: Terminal No. 1

Fig. 1: Distributor Wiring Harness Connector Terminal ID (240SX)

IDLE SPEED AND IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. Improper setting of ignition timing and idle speed may cause driveability problems and/or false setting of trouble codes.

4-CYLINDER IDLE SPEED AND CO LEVEL

• 240SX
  • Idle RPM (With throttle position sensor connected.): 650-750 (Automatic transmission/transaxle in Neutral.)
  • Idle RPM (With throttle position sensor disconnected.): 600-700 (Automatic transmission/transaxle in Neutral.)
  • Maximum CO Level (Measured in Self-Diagnostic Mode II.): 7.0%

4-CYLINDER IGNITION TIMING (Degrees BTDC @ RPM)

• 240SX
  • Man. Trans.: 18-22 @ 700-800
  • Auto. Trans. (Automatic transmission/transaxle in Neutral.) : 18-22 @ 700-800

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Nissan 240sx S13

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