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Idle manifold vacuum questions: 3.5L Taurus


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All, I've been working through a bug that has my 2010 running rough. According to the codes, it had low starting fuel rail pressure (lift pump) and a cylinder misfire. I changed the plugs, and cleaned the injectors. The car is still running rough(rich?) and is showing 10"Hg (PID through the OBDII scan read). It smokes copiously, especially underload.


I pulled the upstream O2s to check function in Open Loop and the car runs better, but still smokes. In closed loop, the fuel trims quickly run to -30 (maximum allowed) on both banks.


What could be causing this?


The OBDII ports show full function (sensors vary based on conditions) for:


Throttle position(all sensors)

MAP - varies between boost and up to 28"Hg, settles at 10 at Idle

Fuel rail pressure (High side) varies from 65psi up to 1500 (maximum I can see at light/medium throttle)

IAT reads through the range

ECT reads through the range



Does this sound like a mechanical problem or a faulty sensor?

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What plugs are you running? Most of us have changed to the SP534 plugs gapped at .030. Don't know if that will help but it's something to consider because a fair amount of folks have discovered a big variation in plug gaps. As far as the others, don't have enough knowledge to give you any input.

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