Engine Stutter while driving

My engine seems to run normal when idling... usually idles around 800rpms... but when driving the engine stutters, notably when I am cruising around town (under 40mph, and between 1000-2000rpms)...
however when I am on the highway or going at speeds faster than 40mph the engine runs smooth. I have a 2001 focus ZTS, just had plugs & wires done and the fuel pump replaced. I'm not sure what the problem could be - mechanic says nothing is coming back to him on the diagnostic computer... Thanks for your help!
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I also have a US 2001 ZTS and had a problem just like that--except that my Check Engine Light was on so the mechanic could pull a code from it. It turned out to be a fairly common issue--a faulty differential pressure sensor. Replaced--all is well.
Poor us--I also had a fuel pump replaced before my stuttering issue arose. I hope Ford's extended warranty on the pump applied to you, too.
Fuel filter replaced with the new pump? Are you at 100k miles to have been due for the plugs?
Craig
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The fuel pump was covered under a technical service bulliten - so that was great - although my car was out of commission for a month because I didn't know there was a TSB on the fuel pump. It would be nice if they notified us of those by mail, like the recalls, but unfortunately they don't! Not sure if my fuel filter was replaced as well... I would assume so but I'll have to check my records. Mechanic recommended having the plugs & wires replaced last fall, but I just recently had them done - my focus is at 75k miles - and the plugs were blackened... definitely past due for replacement!
Thanks for your input - I'll have the differential pressure sensor checked this week. Check engine light is not on but my mechanic will look into it if I ask him to.
Thanks again!
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snipped-for-privacy@gmail.com writes

Coilpack?
--
Paul Giverin

British Jet Engine Website:- www.britjet.co.uk
  Click to see the full signature.
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This is a well known problem in the focus community, just as craig said its the DFPE sensor. It measures the difference between the intake manifold and exhaust back pressure. It's what controls the EGR system. You can either replace the DFPE sensor for around 80 bux, or just block off the EGR System. One is legal and expensive, the other is illegal and cheap lol
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snipped-for-privacy@gmail.com wrote:

Funny this would be an issue at this moment....I have my new sensor right next to me. $31.11 (U.S.), from a Ford dealer, no less.
"One F63Z-9J459-AA, Control Valve. Contents made in Mexico"
Ron
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