Question: What Causes A Small Engine To Rev Up And Down?

How do you fix an idle surge?

The cure for this condition is to clean the valve with some aerosol throttle cleaner or engine top cleaner.

Here’s how to clean the IAC valve: Disconnect the air intake ductwork from the throttle body.

Start the engine, then increase and hold the idle speed to 1,000 to 1,500 rpm..

How do you adjust the idle speed on a Briggs and Stratton engine?

How to Adjust the Idle on a Briggs & Stratton Lawn MowerLoosen the set screw in the center of the air filter with a flathead screwdriver. … Tighten the idle adjustment screw, found on the side of the carburetor, by turning it clockwise just to the point where you feel it lightly touching the seat of the carburetor.More items…

How do you adjust the governor on a Briggs and Stratton 19.5 hp?

First, loosen the arm until it is moving freely. Next, open the throttle to full capacity while making a note of which direction the arm moves in when the throttle moves through it. Once the throttle is fully opened, move the governor shaft in the same direction the governor arm traveled.

What causes an engine to hunt and surge?

Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem. Cleaning/overhauling the carburettor, adjustment of the governor, and/or changing the air filer may be required.

Why is my car revving on its own?

It sounds like you may have a dirty or failing idle air control valve. … This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage.

What does surging mean?

verb (used without object), surged, surg·ing. to rise, roll, move, or swell forward in or like waves: The sea surged against the shore. The crowd surged back and forth. to rise as if by a heaving or swelling force: Blood surged to his face. Electricity. to increase suddenly, as current or voltage.

Can bad spark plugs cause surging?

Surging and Lagging Another good indication that your spark plugs are dirty or worn is if your vehicle experiences surges of speed, resulting in a jerking acceleration. These surges occur because your spark plugs are not igniting the fuel in your engine at the proper rate, resulting in an uneven speed.

What would cause an engine to surge?

If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.