Riviera V6-231 3.8L Turbo VIN 3 4-bbl (1982)
of GM Top Engine Cleaner or equivalent, when properly used, should correct spark knock caused by carbon build-up. If the condition returns, determine
what is causing the excessive carbon build-up. Leaking intake valve stem seals should not be overlooked.
FUEL
This engine is designed to operate on a fuel with, and octane rating of 87; anything less can cause engine spark knock. (See Owner's Manual for an
explanation of octane rating and high altitude octane rating).
IGNITION TIMING
Excessively advanced ignition timing can cause a ping or spark knock condition. This knock is the result of premature combustion of the air fuel mixture
working against the rotation of the engine.
ITEMS WHICH CAN AFFECT IGNITION TIMING AND CAUSE SPARK KNOCK
1.
Base ignition timing too far advanced.
2.
Abnormally high engine operatihg temperature.
3.
Check for proper operation of:
^
Coolant Sensor
^
Map Sensor
^
Baro Sensor
4.
Check for correct distributor wave washer.
5.
Unshielded EST wiring must be routed at least one inch from any spark wire.
ITEMS WHICH MAY CAUSE A LEAN FUEL MIXTURE
EGR System:
1.
The EGR system is designed to introduce exhaust gases through the intake manifold into the engine cylinders. These exhaust gases lower the
combustion temperatures which in turn reduce oxides of nitrogen to an acceptable level. Therefore, improper EGR system operation can cause a
lean air fuel mixture which permits excessively high combustion temperatures to develop. The excessively high combustion temperatures result in
the igniting of the lean air fuel mixture prior to spark plug firing, causing the engine to ping or spark knock.
Check for:
^
Proper operation of EGR control solenoid.
^
Proper operation of EGR cutout relay.
Stall testing the engine with foot on brake pedal will cause EGR cutout relay to energize and cutout EGR, causing engine to spark knock. This is a
normal condition.
^
Proper operation of EGR valve.
^
Correct EGR valve application for engine.
^
Plugged EGR passages in the cylinder head or intake manifold.
EGR system diagnosis can be found on Page 6E-63 and EGR valve check on Page 6E-49 of the 1982 Chassis Service Manual.
2.
Plugged, or pinched or leaking vacuum hoses.
3.
Proper operation of Early Fuel Evaporation (EFE) Valve.
4.
Restricted fuel system, i.e.; plugged fuel filter, etc.
ADDITIONAL CAUSES OF DETONATION
^
Low back pressure (removed catalytic converter or beads).
^
Stuck thermal.
^
Lean carburetor (secondaries stuck closed), stuck metering rods.
