Skip the auto shop - Our mechanics make house calls

Q: trying to figure out misfire or fuel system problem

asked by on

i have a 3rd engine mustang with around 140000k I believe and its losing power when I accelerate. It happens in all gears and at all speeds. And sometimes leaves me with a rough idle. It shakes and only seems to have maybe 30-40% of its normal power. It shakes and sputters I can feel it in the steering wheel. It also leaves an unburnt fuel smell when I get out. Sometimes puts out white smoke out the exhaust. Not heavy just a light amount. Sometimes while it is sputtering it will act like it caught the gear and will pick up like normal when I accelerate but after I let go of the pedal it sputters again. It will only happen maybe 1 out of every 50 times I press the pedal. I changed 7 of 8 spark plugs (a bolt for the cool was rounded off didn't have the socket for it) and no change. I turned off the fuel system from the trunk and let it die then turned it back on and that seemed to fix it! But then today (about 2 days later) it starts happening again.

My car has 140000 miles.
My car has an automatic transmission.

When the problem is happening you would need to have fuel pressure checked to see if the pressure is low and if the filter and pump needs to be replaced. If you have an oil bath type of air filter then you may have a contaminated mass airflow sensor and you may need to replace it or try cleaning it first. Also, use a paper style filter instead. If you need some help with this, consider YourMechanic, as a certified technician can run these checks and diagnose your misfiring 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: Starter only clicking

The most likely cause is that the starter motor or the relay is not making contact; a mechanic should check for power from the relay to the starter. I recommend having a mechanic, such as one from YourMechanic, inspect the...

Q: I am looking to buy a 2000 lincoln LS with 186k miles on it. The only issue is that the owner told me that he gets misfire codes

The codes P0302 and P0307 are misfires on cylinders 2 and 7. I agree that you should have a tune-up on the car if you decide to purchase it. You would need to have the spark plugs replaced and the...

Q: Car won't turn over but has new battery

YourMechanic next door was most likely correct and you have a problem with the key anti-theft system disabling the vehicle. You will either have to have a specialized locksmith come to you, program the key and make new ones, or...

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...