Engine Vacuum Test Quiz

What is a typical vacuum reading for a healthy engine at idle?

• 5–10 in. Hg

• 10–15 in. Hg

• 17–21 in. Hg

• 25–30 in. Hg

Which tool is used to test engine vacuum?

• Timing light

• Fuel pressure gauge

• Compression tester

• Vacuum gauge

Where do you connect the vacuum gauge?

• Valve cover

• Exhaust manifold

• Intake manifold vacuum port

• Radiator hose

What does a rapidly fluctuating vacuum needle at idle likely indicate?

• Normal engine operation

• Leaking valve or valve guide

• Faulty fuel pump

• Restricted air filter

A slow and steady drop in vacuum when accelerating may suggest:

• Normal engine performance

• Exhaust restriction

• Dirty spark plugs

• High fuel pressure

A steady low vacuum reading (e.g., 12 in. Hg) could mean:

• Perfect combustion

• Late valve timing

• Rich fuel mixture

• Proper ignition

Why should you warm up the engine before performing a vacuum test?

• To lubricate the vacuum gauge

• To stabilize vacuum readings

• To reduce fuel pressure

• To cool the radiator

What does a sudden drop and recovery in vacuum suggest?

• Weak spark

• Misfire

• Sticky valve

• Cracked manifold

What could a vacuum reading of 0–5 in. Hg at idle indicate?

• A clogged air filter

• Severe vacuum leak

• Normal idle

• Strong valve seals

What happens to engine vacuum when you open the throttle suddenly?

• It increases sharply

• It decreases briefly

• It remains unchanged

• It becomes erratic permanently