• Tiny
  • SsgtManley
  • 2003 Ford Focus

Engine Performance problem
2003 Ford Focus 4 cyl Two Wheel Drive Automatic 78000 miles

My car jerks and hesitates when I hit the gas. Alot of people are telling me that it could be my fuel filter or my fuel pump any ideas

Thursday, August 28th, 2008 AT 10:41 AM

1 Answer

  • Tiny
  • renaudTN
  • Member

Could be all these things, but it could be many other things as well.
Is your 'check engine' light on?
I would start by checking for DTCs.
You could have a misfire going on (in which case further diagnostic will be necessary).

Possible causes include: - Dirty or leaky fuel injectors
- Bad MAP (manifold absolute pressure) sensor (I'm not sure if Focus have this sensor though)
- Bad TPS (throttle position) sensor
- Bad or dirty MAF (mass airflow) sensor
- Low fuel pressure
- Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)

and in some instances. Bad fuel!

There is a few easy things that you can do to help diagnose and maybe fix your problem: - Do a fuel pressure test. This will tell you if your problem comes from a lack of pressure (due to a bad pump, filter, damage fuel line, regulator etc).

If pressure is too low: - your pump output could be too low (weak pump, low voltage to the pump)
- or your filter is clogged (when was the last time you replaced it? I think Ford recommends replacing the fuel filter on focus every 30,000- 35,000 miles). Although it's not a very accurate test, you can try to remove it and blow thru it to check.
- or your fuel pressure regulator is messed up (disconnect the vacuum line from the regulator and check for gas in it; if there's gas in it, the diaphragm in the regulator is messed up and you need to replace the regulator).
- you could also have a leak somewhere including leaky injectors.
- it could be your inlet filter sock that's clogged. (If you replace your fuel pump, make sure you replace the sock as well)

Other things you can do: -Buy some electronic cleaner, remove the air duct from the throttle body and clean your MAF.
- Put some fuel system cleaner in your tank to clean fuel injector and fuel system (put it in a full tank).

- check for a vacuum leak (intake manifold, and vacuum hoses, throttle body, EGR valve etc)

Good luck!

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Thursday, August 28th, 2008 AT 5:01 PM

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