A8: Engine Performance

Front 1

Symptom:
A heavy thumping noise when started after sitting overnight.

Back 1

Cause:
The heavy thumping noise when the engine is first started may be caused by worn main bearings,

Front 2

Symptom:
a heavy clicking noise at higher engine speed

Back 2

Cause:
Worn camshaft lobes may cause a heavy clicking noise at higher engine speeds.(appox. 2000 rpm)

Front 3

Symptom:
a light rapping noise at idle speed

Back 3

Cause:
Loose piston pins may cause a light rapping noise at idle speed

Front 4

Symptom:
a light clicking noise at idle and low speed

Back 4

Cause:
sticking or worn valve lifters may cause a light clicking noise at idle and low speed.

Front 5

Symptom:
a sharp metallic rapping noise that worsens during acceleration

Back 5

Cause:
Piston rings or ring ridge

Front 6

Symptom:
a heavy thumping noise with the engine idling

Back 6

Cause:
Loose flywheel bolts

Front 7

Symptom:
an exhaust "puff" at regular intervals while idling

Back 7

Cause:
misfire from compression, ignition, or fuel system problem

Front 8

Symptom:
blue exhaust smoke

Back 8

Cause:
Oil consumption

Front 9

Symptom:
Black exhaust smok

Back 9

Cause:
Rich A/F ratio

Front 10

Symptom:
Excessive sulfur smell on Catalytic converter equipped vehicle.

Back 10

Cause:
Rich A/F ratio

Front 11

Symptom:
A steady vacuum gauge reading of appox 14 in at idle

Back 11

Cause:
Late ignition timing, or intake manifold leak

Front 12

Symptom:
Vacuum gauge holds steady at 20 in with engine idling

Back 12

Cause:
Normal operation

Front 13

Symptom:
Vacuum gauge reading varies between 20 and 14 in at idle

Back 13

Cause:
sticky valves

Front 14

Symptom:
Vacuum gauge reading floats between 17 and 21 in at idle

Back 14

Cause
Rich or lean A/F ratio

Front 15

Symptom:
During a power balance test one cylinder causes much less RPM drop than the others at idle, but causes a similar rpm drop at 2000 rpm

Back 15

Cause:
A lack of rpm decrease during the cylinder power balance test indicates the cylinder is misfiring. Because the cylinder misfire disappeared at 2,000 rpm, an intake manifold vacuum leak is indicated.

Front 16

Symptom:
During a compression test, one cylinder has much less compression than the others, During the wet test, the compression raises dramatically.

Back 16

Cause:
Worn piston rings cause an increase in compression readings during the wet test,

Front 17

T/F
a bent intake valve may cause excessive air to escape through the throttle body during a leak down test

Back 17

True
During a cylinder leakage test, excessive leakage and air escaping from the throttle body may be caused by a bent intake valve

Front 18

T/F
a bottomed intake valve lifter may cause excessive air to escape through the throttle body during a leak down test.

Back 18

True
During a cylinder leakage test, excessive leakage and air escaping from the throttle body may be caused by a bottomed intake valve lifter.

Front 19

T/F
Some engine analyzers compare test results to specifications and indicate readings that are out of spec

Back 19

True
Some engine analyzers compare test results to specifications and indicated readings that are
out of specifications.

Front 20

T/F
Some engine analyzers provide the option of manual or automatic test modes.

Back 20

True
Manual or automatic test modes may be selected on some enginelyzers

Front 21

T/F
an exhaust leak may cause inaccurate emission analyzer readings

Back 21

True
A leak in the exhaust system may cause inaccurate emission readings.

Front 22

T/F
with the tester probe in the tailpipe, the analyzer provides accurate hc and co readings from the engine

Back 22

False
With the emissions analyzer probe in the tailpipe, the analyzer indicates the emissions coming out of the converter, which could be considerably lower than the emissions coming out of the engine.

Front 23

T/F
the catalytic converter reduces co2 and o2 levels

Back 23

False

Front 24

T/F
If the exhaust valve clearance is less than spec, premature valve burning may occur

Back 24

True

Front 25

T/F
the piston should be at TDC exhaust when the valves are adjusted

Back 25

False

Front 26

T/F
Excessive intake or exhaust valve clearance causes a clicking noise with the engine idling

Back 26

True

Front 27

T/F
the piston should be at TDC compression when the valves are being checked.

Back 27

True

Front 28

When verifying camshaft timing, the #1 piston is at TDC exhaust, with the exhaust valve (...) and the intake valve (...)

Back 28

with the piston at TDC on the exhaust stroke, the intake valve should be starting to open and the exhaust valve should be starting to close.

Front 29

The hall effect pickup in a distributor can be checked by...

Back 29

connecting a votmeter from the signal wire to ground while cranking

Front 30

on an EI ignition system coil pack, the negative side of each primary winding is connected to...

Back 30

The module or PCM

Front 31

on an EI ignition system coil pack, the ends of the T
secondary winding are connected ...

Back 31

from the coil tower to the primary terminal

Front 32

on an EI ignition system coil pack, 12v are supplied to...

Back 32

the positive side of each primary winding

Front 33

T/F
ignition timing must be adjusted on electronic distributor less ignition systems.

Back 33

False

Front 34

T/F
In order to set basic timing on some fuel injected engines with a distributor, the pcm must be in the limp mode.

Back 34

True