I'm not exactly sure what the order of importance is for the IAT readings, but I also didn't think the coolant temp sensor was high priority until I had one fail. Truck ran like it was sucking marbles into the intake.

 

Unplug your IAT and see how it runs.

 

From the service manual:

During Open Loop modes, the PCM receives input
signals and responds only according to preset PCM
programming. Input from the oxygen (O2S) sensors
is not monitored during Open Loop modes.
During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.

 

And some about a couple of the important (from a performance standpoint at least) open loop mode operations:

ACCELERATION MODE
This is an Open Loop mode. The PCM recognizes
an abrupt increase in throttle position or MAP pressure
as a demand for increased engine output and
vehicle acceleration. The PCM increases injector
pulse width in response to increased throttle opening.

WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the PCM receives the following
inputs.
² Battery voltage
² Crankshaft position sensor
² Engine coolant temperature sensor
² Intake manifold air temperature sensor
² Manifold absolute pressure (MAP) sensor
² Throttle position sensor (TPS)
² Camshaft position sensor signal (in the distributor)
During wide open throttle conditions, the following
occurs:
² Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off. The PCM ignores the oxygen sensor input
signal and provides a predetermined amount of additional
fuel. This is done by adjusting injector pulse
width.
² The PCM adjusts ignition timing by turning the
ground path to the coil on and off.

 

I need to find a friend that has a dyno.....

 

FYI, here are all the modes the PCM recognizes, and which are open versus closed loop operations:

² Ignition switch ON -open loop
² Engine start-up (crank) - open loop
² Engine warm-up - open loop
² Idle - closed loop
² Cruise - closed loop
² Acceleration - open loop
² Deceleration - open loop
² Wide open throttle (WOT) - open loop
² Ignition switch OFF - n/a

 

He wes being towed by a Prius.

 

wow.air temps play a big roll in a speed density system.how would the pcm know the density of the incoming air.the map sensor measures the volume not the o2's.speed density=rpm,map,temp.the o2's just fine tunes the mix in closed loop.

 

Sorry, but speed density systems do not use temperature to determine the density of the air (i.e. barometric pressure). This is what the MAP sensor does. Density = mass divided by volume. Temp has nothing to do with determining density. It is MAF systems that utilize temp in fuel calculations to a greater degree because a MAF sensor measures both temp and volume (and some measure velocity too), but our trucks are not MAF.

You are correct about the o2's, which is exactly what I stated out of the service manual.

 

correct formula for density of a solid.air is not a solid its a gas.one would need to ad in the ideal gas law when calculating VE tables.P*V = n*R*T.combining both equations you get density=P(pressure)/R(GAS/constent)*T(TEMP).speed density VE TABLES will be N(estimated)=PV/RT.VE table are calculated using this equation.VE tables are not the only thing that controls the fuel.you have heard the saying "hot air rise's".density,volume,mass are not all the same.MAF sensor is MASS air flow.not volume air flow.anyway cold air is free horsepower anyway you slice it