Engine Vacuum Test - Snapping the Throttle

This shows an example of a good engine's response to having the throttle snapped. Notice how it climbs well above the steady state of 21-22 in Hg and then drops back down to it's steady vacuum after the throttle is snapped.

Typically, dropping to 0-3, typically more like 2-3 and then climbing up to about 25 then dropping back to 17-22 is ideal.

If your car doesn't do this when tested, it may have worn rings or valve seals.

Category:

Autos & Vehicles

Tags:

• engine vacuum
• check engine health

[TunerUniversityCom]

Low vacuum is an immediate clue to a plugged exhaust. To check further, run the engine at about 2500 rpm for about 15 seconds. If vacuum drops during this period and does not increase when you close the throttle, you're almost certainly looking at a restricted exhaust.

This particular engine has a brand new wide open exhaust, the reading also is consistent with good and new engines that I have done in the area.

Note that there is some variance in vacuum readings due to altitude, etc.

[ApuNehru]

Actually the reading seems to indicate a restricted exhaust.