Pontiac Fiero 1988 Service Manual page 511

6 E 2 - B - 2 DRIVEABILITY A N D EMISSIONS - FUEL INJECTION (TBI)
INTERMITTENTS
Problem may or may not turn "ON" the "Service Engine Soon" light, or store a code.
DO NOT use the Trouble Code Charts in
Section "A" for intermittent problems. The fault
must be present to locate the problem. If a fault is
intermittent, use of Trouble Code Charts may result
in replacement of good parts.
• Most intermittent problems are caused by
faulty electrical connections or wiring.
Perform careful check of suspect circuits
for:
Poor mating of the connector halves, or
terminals not fully seated in the connector
body (backed out).
Improperly formed or damaged terminals.
All connector terminals in problem circuit
should be carefully reformed to increase
contact tension.
Poor terminal to wire connection. This
requires removing the terminal from the
connector body to check as outlined in the
Introduction to Section "6E".
• If a visual (physical) check does not find the
cause of the problem, the car can be driven with
a voltmeter connected to a suspected circuit or a
"Scan" tool may be used. An abnormal voltage
reading when the problem occurs indicates the
problem may be in that circuit. If the wiring and
connectors check OK and a Trouble Code was
stored for a circuit having a sensor, except for Codes
44 and 45, substitute a known good sensor and
recheck.
• Loss of trouble code memory. To check,
disconnect TPS and idle engine until "Service
Engine Soon" light comes on. Code 22 should be
stored, and kept in memory when ignition is
turned "OFF" for at least 10 seconds. If not, the
ECM is faulty.
• An intermittent "Service Engine Soon" light
and No Trouble Codes may be caused by:
- Electrical system interference caused by a
defective relay, ECM driven solenoid, or switch.
They can cause a sharp electrical surge.
Normally, the problem will occur when the
faulty component is operated.
- Improper installation of electrical options, such
as lights, 2-way radios, etc.
- EST wires should be routed away from spark
plug wires, ignition system components, and
generator. Wire for CKT 453 from ECM to
ignition system should be a good ground.
- Ignition secondary shorted to ground.
- CKTs 419 ("Service Engine Soon" light) and
451 (Diagnostic Test) intermittently shorted to
ground.
- ECM grounds.
HARD START
Definition:
Engine cranks OK, but does not start for a long-
time. Does eventually run, or may
start
but immediately dies.
• CHECK:
- For water contaminated fuel.
- Fuel system pressure CHART A-7.
- TPS for sticking or binding should read less
than 1.25 volts on a "Scan" tool.
- EGR operation. CHART C-7.
- Fuel pump relay - Connect test light between
pump test terminal and ground. Light should be
on for 2 seconds following ignition "ON". If not,
refer to CHART A-5.
- For a faulty in-tank fuel pump check valve
which would allow the fuel in the lines to drain
back to the tank after the engine is stopped. To
check for this condition:
1. Ignition "OFF".
2. Disconnect fuel line at the filter.
3. Remove the tank filler cap .
4. Connect a radiator test pump to the line and
apply 103 kPa (15 psi) pressure. If the
pressure will hold for 60 seconds, the check
valve is OK.
• Check ignition system for:
- Proper Output with ST-125.
Bare and shorted wires.
Crank sensor resistance or connections.
Loose ignition coil connections.
Spark plugs, wet plugs, cracks, wear,
improper gap, burned electrodes, or heavy
deposits.