Skip the auto shop - Our mechanics make house calls

Q: Car bucks, jerks, and idles rough - 1991 Ford Mustang

asked by on

My car seems like it isn't getting any gas. I can press on the throttle and it stalls, i let off the throttle and it bucks and jerks like something is misfiring. I press it to the floor and it just chokes. It does idle rough also, it goes from high to low. I put new spark plugs in and it's still doing the same thing.

My car has 240000 miles.
My car has an automatic transmission.

Hey there. This may be a sign of a failing idle air control valve. The idle air control valve is located on or near your intake manifold and monitors the air intake as it is mixed with fuel prior to being injected into the engine. This valve is controlled by the vehicle’s computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage.

When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. However, when the engine RPM drops below the normal range of 750-800 RPM (for most cars), this may indicate a dirty or faulty idle air control valve. In cases where this valve is clogged or failing, your vehicle will stall instead of slowing to an idle after the release of the throttle. If you would like to have this taken care of, a qualified professional from YourMechanic can come to your location to replace the idle control valve for you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car idling high and rough

The cleaning of your throttle body may have caused a vacuum leak in the intake system. It's also possible that an improper hose reinstallation to the throttle body is causing unmetered air between the throttle body and the mass air...

Q: Is it the clutch master cylinder, pressure plates, or both?

Hi, your clutch hydraulics are the most likely problem, and the slave cylinder is more likely to fail first. Since it essentially leaks on the ground, it is more difficult to recognize this component as your first failure point. The...

Q: Car is not firing on the first two cylinders

This is generally related to spark problems when it is more consistent. Spark related problems generally will result from things like ignition coils, crankshaft position sensor, spark plugs, spark plug wires or ignition modules not working properly. As you know,...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.