Q: Mileage is getting progressively worse

asked by on

I recently had the plugs, plug wires and timing belt replaced. My mileage was 20 mpg before the work and has dropped to less than 10 mpg. There is a significant loss of power and the engine bogs down and runs rough.

My car has 250000 miles.
My car has an automatic transmission.

Hi there. This can be caused by a number of things. If it occurred right after the work was done then you may want to have it double checked. They may have used poor quality wires or the wrong spark plugs.

It is also possible that you have a leaking fuel pressure regulator or a fuel injector as they will also cause this.

If the engine runs smooth but just lacks power and MPG then you may also be looking at a bad catalytic converter. If the vehicle was running bad before the tune-up then this is possible. A back pressure test would need to be performed to verify if it is bad.

If you want to have this done, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your decreasing gas mileage and repair it as necessary.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Mileage is getting progressively worse

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: OBll CODE : P1899

Hi there. As the service manual reads, the resistance between pin 2 on the range switch and pin 6 black PCM connector must be checked for less than 5 ohms of resistance. Any more than 5 ohms of resistance and...

Q: My 2007 Nissan Altima is not accelerating properly... when I punch gas the rpms go up but the car doesn’t accelerate

It sounds like a problem with your transmission. It may not be shifting out of first gear. This could be due to any number of issues but may have something to do with the check engine light on your dashboard....

Q: Thermostat malfunction code read

The Code that was set might have been P0126. The engine cooling thermostat maintains optimal engine temperature. Inasmuch as the PCM can measure actual temperature from other sensor inputs (such as the coolant temperature sensor), the functioning of the thermostat...

Related articles

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...
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...
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...