Pontiac Fiero 1988 Service Manual page 274

ENGINE GENERAL INFORMATION 6-3
« Section 6E1 - Carbureted Engines
• Section 6E2 - Fuel Injection (TBI)
• Section 6E3 - Fuel Injection (Ported)
ENGINE MECHANICAL DIAGNOSIS
T h e f o l l o w i n g d i a g n o s t i c i n f o r m a t i o n c o w e r s c o m m o n p r o b l e m s a n d p o s s i b l e c a u s e s . W h e n
t h e p r o p e r d i a g n o s i s i s m a d e , t h e p r o b l e m s h o u l d b e c o r r e c t e d b y a d j u s t m e n t , r e p a i r o r p a r t
r e p l a c e m e n t a s r e q u i r e d . R e f e r t o t h e a p p r o p r i a t e s e c t i o n o f t h e m a n u a l f o r t h e s e p r o c e d u r e s .
E X C E S S I V E OIL L O S S
External oil leaks. Tighten bolts and/or replace
gaskets and seals as necessary.
Improper reading of dipstick. Check oil with car
on a level surface and allow adequate drain-down
time.
Improper oil viscosity. Use recommended S.A.E.
viscosity for prevailing temperatures. See
Owner's Manual for proper specifications.
• Continuous high speed driving, and/or severe
usage such as trailer hauling, will normally cause
decreased oil mileage.
• PCV system malfunctioning.
c Valve guides and/or valve stem seals worn, or
seals omitted. Ream guides and install oversize
service valves and/or new valve stem seals.
• Piston rings broken, worn, or not seated. Allow
adequate time for rings to seat. Replace broken
or worn rings, as necessary.
• Piston improperly installed or misfitted.
LOW OIL P R E S S U R E
Slow idle speed. Set idle speed to correct •
specification, if not ECM controlled. @
Incorrect, or malfunctioning, oil pressure switch.
m
Incorrect, or malfunctioning, oil pressure gage. •
Replace with proper gage.
m
Improper oil viscosity, or diluted oil. Install oil of •
proper viscosity for expected temperature, or
install new oil if diluted with moisture or #
unburned fuel mixtures.
Oil pump worn or dirty.
Plugged oil filter.
Oil pickup screen loose or plugged.
Hole in oil pickup tube.
Excessive bearing clearance. Replace if necessary.
Cracked, porous or plugged oil galleys. Repair or
replace block.
Galley plugs missing or misinstalled. Install
plugs, or repair as necessary.
V A L V E TRAIN NOISE
Low oil pressure. Repair as necessary
preceding diagnosis for low oil pressure.)
Loose rocker arm attachments,
repair as necessary.
Worn rocker arm and/or pushrod.
(See
Inspect and
Broken valve spring.
Sticking valves.
Lifters worn, dirty, or defective. Clean, inspect,
test and replace as necessary.
Camshaft worn, or poor machining. Replace
camshaft.
Worn valve guides.
ENGINE KNOCK DIAGNOSIS
KNOCKS COLD AND CONTINUES FOR T W O TO THREE MINUTES
INCREASES WITH T O R Q U E
Vacuum operated EFE engines may have valve
knock. Replace EFE valve.
Flywheel contacting splash shield. Reposition
splash shield.
Loose or broken balancer or drive pulleys.
Tighten, or replace as necessary.
Excessive piston to bore clearance. Replace
piston.
Cold engine piston knock usually
disappears when the cylinder is grounded
out. Cold engine piston knock which
disappears in 1.5 minutes should be
considered acceptable.