Ford Focus Runs Rough at Idle

Problem May Be Water in Differential Pressure Feedback Sensor

Question: Ford Focus Runs Rough at Idle

Hi, I have a 2000 Ford Focus LX, 2.0 liter SPI, not dual-cam, automatic transmission with about 71,500 miles. My problem has me stumped. The car idles rough, whether hot or cold, but it's fine when the gas pedal is depressed. I've changed the spark plugs, plug wires, fuel filter, oxygen sensor, air filter, had the fuel injectors cleaned at the dealership, and poured many bottles of injector cleaner into the tank.

That seems to do the trick until I get close to empty, but will continue if I don't pour another bottle in during the next fill up. I use Chevron gas, if that makes a difference. I've been thinking it's my EGR system, so I unplugged the line from the solenoid to my EGR valve, and no difference, although I feel a vacuum pulsation coming from the solenoid at idle. I hear that may be bad. Is there anything else I can try before I take the car in and dump a couple hundred dollars on it? I'd like to fix it myself.

Thank you,

Answer: Possibly Water in Differential Pressure Feedback EGR Sensor

There are two possible problems that could be creating this rough idle. If my first choice doesn't solve the problem, consider the second one.

First, I'm thinking you're probably right about it being an EGR problem. The 2000 to 2003 Ford Focus has a problem with water getting into the Differential Pressure Feedback EGR (DPFE) Sensor.

The specific fix for this depends on when the car was built.

The one procedure they all have in common is to seal the DPFE Sensor. There are two types of DPFE Sensor mountings. For the ones mounted on the firewall:

Firewall Mounted DPFE Sensor

  1. Remove the DPFE.
  2. Fold the insulation on the partition wall 900 downward so it lays over the top of the EVR.
  1. Reinstall the DPFE such that the insulation is trapped in place between the bottom of the DPFE and the top of the EVR. Tighten to 36 +/- 6 lb-in. (4.1 +/- 0.7 N.m)
  2. Verify the DPFE and EVR hoses are fully seated.

Tube-mounted DPFE Sensor

  1. Remove the EVR solenoid.
  2. Trace out a 2.5" wide x 3" tall rectangle in the insulation, starting from the bottom, and just outside of the EVR mounting lugs.
  3. Cut vertically upward from the bottom along each of the two vertical lines, stopping at the line drawn horizontally.
  4. Fold the section of insulation 900 upward.
  5. With the insulation held up, reinstall the EVR solenoid. Tighten to 36 +/- 6 lb-in. (4.1 +/- 0.7 N.m) 

Another Possibility: Vacuum Leaks

Another possibility common to all 2000 to 2004 Ford, Lincoln, and Mercury products is a vacuum leak. So, a through check of all the vacuum lines and hoses is a good idea.

Troubleshooting Idle Problems: See common symptoms and causes for idling too low, too high, rough idle, and stalling.

Additional Information provided courtesy of AllDATA