Skip the auto shop - Our mechanics make house calls

Q: Bad gas mileage, high idling

asked by on

I'm getting really bad gas mileage while driving my truck. It has now dropped to 7 MPG. When I'm driving on the highway, it runs great. However, it is idling high at the 1000-1500 RPM range. When I'm starting it up, especially when it's warmed up, I have to floor the gas pedal. It starts to sputter a bit before it gathers power. I've been told that many things can cause this, from throttle position sensor, MAF sensor to fuel pressure regulator etc. What do you think I should do to improve the gas mileage and overall performance of the vehicle?

A: Idle speed for your vehicle should be betwe...

Idle speed for your vehicle should be between 725 and 750 RPM. So, it is idling high. Common causes for this include vacuum leaks and a faulty idle air control (IAC) valve. Either of these issues could also affect fuel economy. However, there are many other potential causes as well. The first step is to retrieve any stored Diagnostic Trouble Codes (DTCs) which serve as a starting point for any further diagnosis. I suggest you have a trained professional, such as one from YourMechanic, diagnose your poor gas mileage and repair your vehicle firsthand.

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

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: Sluggish acceleration during quick speed increase

The intake variable runner control may be stuck in the wrong position and would need to be checked to see if it is able to move. The control valve for this or the solenoid for the variable valve timing may...

Q: Cranks, has spark and fuel, won't start

Hey there. It's quite possible that either the distributor has moved and the timing is off; or plug wires are not correctly installed to the right cylinders. Believe it or not, that's very common. You might want to verify that...

Q: Slight smell of gas or oil and poorer mpg fuel efficiency

This may be a result of a faulty oxygen sensor. As you may know the oxygen sensors which are part of your emissions system read exhaust gases to determine whether or not the appropriate amount of oxygen is present in...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...