2000 Ford Excort ZX2


Old 12-30-08, 04:14 PM
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Join Date: Dec 2008
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Unhappy 2000 Ford Excort ZX2

Have a ZX2. Anybody have any ideas or had the following problem?

Problem is a P0171 code.

Symptoms: Severe "miss" between 1700 and 2300 RPM when engine is warm and under light load, rough idle, occasionally dies when idleing. Pressing gas pedal (or releasing) gets rid of "miss" at speed. The "miss" could better be described as bucking, sometimes as though you were turning the key on and off rapidly, sometimes mild like a fouled plug.

Known good:

Fuel pressure at rail under all conditions (~35 psi) - checked with gauge.

Suspected okay:

Plugs and wires - inspected
Spark - verified on each plug wire at speed with a timing light - no visual change in strobe
No misfire codes
Vacuum lines visually inspected - no audible leaks either
Throttle position sensor

MAF Sensor

Not sure:
Both O2 sensors cycle between ~0.1 and 0.9 volts about every half to full second at idle - no apparent change when the miss occurs.

Has 186000 miles but runs okay otherwise - decent oil pressure, no smoke or oil consumption...
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Old 12-30-08, 04:35 PM
HotxxxxxxxOKC's Avatar
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Have you checked your PCV valve and hose?
Old 12-31-08, 09:00 PM
Join Date: Dec 2008
Location: Rhode Island
Posts: 182
i second the pcv hose, but look for collapsed hoses too. there
is a leak somewhere it's a common code for a ford. also
could be a failing intake manifold gasket leaking rare but a cause too.

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