Vacuum Gauge Flickers

[Eric_S]

I am trying to smog my 78FJ40 and I decided to hook up a vacuum gauge to the intake manifold. At idle, it flickers, oscillates, vibrates, bounces, etc about 2" What should I look for? It rapidly flickers between 16 and 18".

 

[Michael Hanson]

Check the valves.2 cents Mike

 

[Degnol]

On Fire



You might find that helpful....

 

[Eric_S]

I would say it looks like this, but a lot faster at idle. and between 16 and 18"

LEAKY VALVE: needle drops 2-4 points when valve should close. short circuiting individual spark plugs will indicate cylinder in which the valve is defective, when engine idling.

or it can even look like this...

RETARDED IGNITION: needle gives steady reading between 17 and 19 with engine running at a higher idle speed

 

[k91]

I have the same thing you have......Do you by chance have a loss of power during acceleration?

 

[Eric_S]

I have the same thing you have......Do you by chance have a loss of power during acceleration?

I do not know, my FJ40 has not been street legal in a few years so I have only driven it off road.