Pontiac Fiero 1988 Service Manual page 645

6 E 3 - B - 6 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT)
BACKFIRE
Definition: Fuel ignites in intake manifold, or in
exhaust system, making a loud popping noise.
• CHECK:
Compression - Look for sticking or leaking
valves.
Exhaust gas recirculation (EGR) operation
for being open all the time. See CHART C-7.
EGR gasket for faulty or loose fit.
Valve timing.
Output voltage of Ignition coil using a shop
ocilliscope or spark tester J-26792 (ST-125)
or equivalent.
Spark plugs for crossfire also Inspect
(distributor cap, spark plug wires, and
proper routing of plug wires).
Ignition system for Intermittent condition
See Section"6D" or Section "6E3-C4."
Engine timing - see Emission Control
Information label.
>OOR FUEL E C O N O M Y
Definition: Fuel economy, as measured by an actual road test, is
noticeably lower than expected. Also, economy Is noticeably lower than it
was on this car at one time, as previously shown by an actual road test.
f
!
Check owner's driving habits.
- Is A/C "ON" full time (Defroster mode
"ON")?
Are tires at correct pressure?
Are excessively heavy loads being carried?
Is acceleration too much, too often?
Suggest owner fill fuel tank and recheck fuel
economy.
Suggest driver read "Important Facts on
Fuel Economy " in Owner's Manual.
• C heck for proper calibration of speedometer.
• Visually (physically) Check:
- Vacuum hoses for splits, kinks, and proper
connections as shown on Vehicle Emission
Control Information label.
- Ignition wires for cracking, hardness, and
proper connections.
- Air cleaner element (filter) for dirt or being
plugged.
o Remove spark plugs. Check for cracks, wear,
improper gap, burned electrodes, or heavy
deposits. Repair or replace as necessary.
• CHECK:
Engine thermostat for faulty part (always
open) or for wrong heat range. Using a "Scan"
tool, monitor engine temperature. A "Scan"
displays engine temp, in degrees centigrade.
After engine is started, the temperature
should rise steadily to about 90°C, then
stabilize, when thermostat opens. See
Section "6B".
- Fuel Pressure. See CHART A-7.
Compression. See Section "6A".
Transmission/transaxle converter clutch
(TCC) for proper operation. See CHART C-
8A. A "Scan" should indicate an rpm drop,
when the TCC is commanded "ON".
Exhaust system restriction. See CHART B-1.
DIESELING, RUN-ON
Definition: Engine continues to run after key is
turned "OFF", but runs very roughly. If engine runs
smoothly, check ignition switch and adjustment.
• Check injectors for leaking. See CHART A-7.
• If engine runs smoothly, check ignition
switch and adjustment.