Chart 2 Diagnosis and Identification Characteristics

POSSIBLE CAUSES DIAGNOSTIC/IDENTIFICATION CHARACTERISTICS

Ignition Relay Malfunction Select Monitor display may go blank, Codes
24 and 35.

Cam Angle Sensor Malfunction No signal from cam angle sensor, loose
mounting bolts.

02 Sensor Malfunction Is 02 feedback present warm engine idling, is
heater circuit operating correctly.
Substitution test.

Timing Belt Out of Position Check for recent engine work, cannot be
timed, backfire.

Spark Plug Fouling Black smoke, rough idle.

ISC Valve Sticking Check duty ratio, warm engine, A/C and fans
off. Substitution test.

Idle Adjust Screw Investigate previous repair attempts, look
Mis-Adjusted for evidence of mis-adjustment. Substitution
test.

Throttle Valve Mis-Adjustment See August, 1991 Helpline Update for check
and adjustment tips.

Vacuum Leak Look for out of spec. Select Monitor
readings. Use propane enrichment to locate.

Fuel Pressure Regulator Fuel pressure should change when vacuum hose
Malfunction is pulled from pressure sensor.

Fuel Injector Leakage Intermittent hard starting after cold soak,
with grey or black smoke upon start-up,
condition clears up by itself. Swap test
including fuel gallery pipe to confirm.

Air Flow Meter Malfunction Normal operation is a smooth and gradual
voltage drop down to low end of spec. when
starting cold engine. Swap with known good
one to confirm.

Exhaust Valve Sticking Vacuum gauge reading fluctuation during
occurrence. May happen during start or warm-
up. Excessive engine cranking speed (loss of
compression).

Water Temp Sensor Output Select Monitor reading is abnormal.
Incorrect

Intake Valve Isolate with leak down tester. Fuel
problems.


Chart 2 Diagnosis and Identification Characteristics (cont'd.)


POSSIBLE CAUSES DIAGNOSTIC/IDENTIFICATION CHARACTERISTICS

Fuel Pump Check for electrical signal, operation and
pressure.

Crank Angle Sensor Resistance check, hard or no start.
Malfunction

Abnormal Compression Disconnect injector connector one by one to
identify the cylinder. Excessive crank speed,
check for mechanical problems, use leak down
tester.

Electrical Wiring Poor "Everything" has been checked or replaced,
Connection problem still exists intermittently.

Fuel Problems Suspect improper winter/summer blend, tank
contamination, poor quality

ECU Perform substitution test with known good
unit, confirm by problem transfer using
"failed" unit.