Taurus Idle Problem:
2000 Ford Taurus SEL, V6, 3.0L (182 CID); DOHC, automatic, 125,000mi.
When engine is ‘COLD’ (morning startup and afternoon startup), engine starts immediately then comes to normal idle speed. Within a few seconds engine begins to idle roughly even while idle speed is constant. About one half of the time, the condition is not sever enough to cause stalling, so I can get the car in gear and drive until the engine warms up enough for the problem to go away. The engine runs like the day I bought it when it is hot. The other half of the time, after the engine begins to idle roughly, the RPMs drop and the engine stalls. After several restarts, and running the engine speed up to 2000 RPM for a minute or two I have been able to prevent the stalling and drive until warm-up. When the engine is idling roughly it is enough to shake the car, sometimes it make what I call a loping sound but the RPMs are constant.
About a month ago I bought an OBD II tester and have consistently gotten a DTCs P0171 System Too Lean (Bank 1), and DTC P0174 System Too Lean (Bank 2), and I have also gotten engine misfire codes, (somewhat inconsistently), everything from P0300 (random misfire) to misfire on specific cylinders.
So far I have: (1) changed the gas filter, (2) changed the spark plugs, (3) change all of the ignition coils where I have gotten a misfire DTC for a specific cylinder (three total), (3) replaced the upper intake manifold gaskets (since I had to remove this to get to the spark plugs), (4) changed the EGR gasket (since I had to remove this to get to the spark plugs), (4) checked for obvious vacuum leaks (visually and by touch), (5) tested both key-on and engine-on fuel injector rail pressure, (6) listened for fuel injector valve clicking, and (6) tested the PCV valve by applying a vacuum to the connecting hose.
Changing the fuel filter and spark plugs gave the engine more power (that I had not noticed was lost) but it did not correct the problem. Changing the coil for the first DTC code (P0306) that I received, eliminated an annoying little misfire that I would notice when the engine was hot and at idle, but it did not correct the cold engine problem. Changing the other 3 coils did nothing. I was never able to find any obvious vacuum leaks, all of the injectors seemed to be clicking (so I assume none are sticking) and the fuel pressure test was within spec. Finally, while the PCV valve did move in response to applied vacuum, however it is 12 years old and did not have the crisp clicking noise as it snapped back into place, but it did move freely and go back into position. Why did Ford make this valve so hard to get to on my engine?
I can send one of the diagnostic reports from Innova if I can figure out how to do this.
Help would be appreciated.
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Sunday, February 12th, 2012 AT 3:26 PM