I have a Ford Taurus 3.0 V6 with DOHC<Vin S> motor. I'm having extreme
difficulties witht he idle on the car. In Open Mode (Cold idle) the
car run extremely rough. But when the car gets up to temperature and
the Oxygen sensors are operating in Closed mode the car runs better
but still rough. But in both instances the car is running extremely
Lean. I've check for vacuum leaks, EGR valve. I've cleaned the MAF
sensor and the Idle Air Control valve. I only get the two system codes
(P0171 & P0174), that the car is running lean on both banks. Even
when the car is running, it still running a tad on the lean side, but
at higher RPMS the oxygen sensors seem to be able to make up the
difference. I have check the reading of the MAF and at a hot idle its
reading approximately 3.09 gm/s, which is just slightley outside the
Ford reference values for the 4 valve motor (3.4-4 g/s) and at 2500
rpm its in the range 16 g/s, and the spec values are 13-14 g/s. Since
these are Reference values, I'm not extremely far off these values.
But in an idle, the both the oxygen sensors(1.1 and 2.1) are showing
almost 0 volts (extremely lean). Then if I remove the connector off
the MAF sensor the car will start to idle little rich. Also when you
crank the car up and its cold, the car will idle pretty high to start
with( 2000 rpms) and then slowly drop down to the 1000~700 range.
Also the Idle control valve seems to make alot of noise (whistling). I
know it suppose to allow vacuum out of the Intake. I can't remember
ever hearing it before, but that don't mean anything. I know that the
car will imediately stall if the sensor is disconnected.
If I'm was a betting person I would say that the MAF sensor is at
fault, since this seems the a common Ford problem. The car runs fine
from a drivers prespective, when driving. Just has a nack for stalling
at a red light, or at any complete stop for a period of time(doesn't
just stall, it takes it a few minutes until it get to this point.).
I'm curious if anyone else has had the issue. I'm almost to the Trial
and Error point. But the only problem is they normally do not allow
you to carry back sensors.
The measurement above are from a OBDII laptop interface. Its not a top
of the line model, but one that will work with just about any model
car. And the reference values come from the Ford Technical Service