Pontiac Fiero 1988 Service Manual page 513

6E2-B-4 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)
DETONATION / SPARK KNOCK
Definition: A mild to severe ping, usually worse under acceleration. The
engine makes sharp metallic knocks that change with throttle opening.
> CHECK for obvious overheating problems.
- Low coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted
water flow thru radiator.
- Faulty or incorrect thermostat.
- Inoperative electric cooling fan circuit. See
CHART C-12.
- Coolant Sensor which has shifted in value.
- Correct coolant solution - should be a 50/50
mix of GM #1052753 anti-freeze coolant (or
equiv.) and water.
• CHECK:
- For poor fuel quality, proper octane rating.
- For correct PROM.
- Spark plugs for correct heat range.
- Fuel system for low pressure. See
CHART A-7.
- Check EGR system for proper operation- CHART
C-7.
- For proper transmission shift points. See Section
f t rjtt
- TCC operation. See CHART C-8.
- For incorrect basic engine parts such as cam,
heads, pistons, etc.
- Excessive oil entering combustion chamber.
• Remove carbon with top engine cleaner.
Follow instructions on can.
HESITATION, SAG, STUMBLE
Definition:
Momentary lack of response as the accelerator is pushed down.
Can occur at all car speeds. Usually most severe when first trying to make the
car move, as from a stop sign. May cause the engine to stall if severe enough.
Perform careful visual (physical) check as - Generator output voltage. Repair if less than 9 or
described at start of Section "B". more than 16 volts.
CHECK: -
For open Ignition System ground, CKT 453.
Fuel pressure. See CHART A-7. - Canister purge system for proper operation. See
Water contaminated fuel. Section "C3".
TPS for binding or sticking. - EGR valve operation CHART C-7.
CUTS OUT, MISSES
Definition:
Steady pulsation or jerking that follows engine
speed, usually more pronounced as engine load increases. The
exhaust has a steady spitting sound at idle or low speed.
Perform careful visual (physical) check as
described at start of Section "B".
If Ignition System is suspected of causing a miss
at idle or cutting, out under load:
Refer to appropriate ignition "Misfire" Chart in
Section "C4".
If the previous checks did not find the problem:
Visually inspect ignition system for moisture,
dust, cracks, burns, etc. Spray plug wires with
fine water mist to check for shorts.
Use a "Scan" tool to check for erratic TPS
voltage.
Fuel System - Plugged fuel filter, water, low
pressure. See CHART A-7.
Perform compression check.
Valve Timing.
Remove rocker covers. Check for bent pushrods,
worn rocker arms, broken or weak valve springs,
worn camshaft lobes. Repair as necessary. See
Section 6A.