MarkChai

UPDATE: The issue appears to have been a boost leak at the IAT sensor.

diagnosticator1

It's easy to disregard sometimes, seams that the Turbo would cover the difference in air flow easily, but your experience here indicates not.

cparke

How did you find this? Why TOO RICH only on Bank 1 for an air intake leak?

diagnosticator1

OP noted oily residue at intercooler tank where the IAT sensor is mounted.

cparke

Ok, so if this was a 6-cyl, we'd expect both would have been too rich.

diagnosticator1

with the scenario here, but with the V6, other factors can cause bank 1 and 2 to differ.

cparke

So, Mark must have actually found intake air blowing out of the IAT sensor? I would have thought the reverse---unmetered air entering the system through the IAT sensor.

Also, he said he passed the MAF redline test, yet if he had an IAT sensor boost leak\, shouldn't the redline test have suggested something wrong with the MAF first?

I'm still not out of the woods myself, so answers to these questions are very important to me right now.

diagnosticator1

On a turbocharged engine, when the intake system is pressurized above ambient surrounding atmospheric pressure, if a leak exists, then some of the measured air mass is lost before reaching the cylinders, but the ECU injects enough fuel for all of the measured air mass.
However, due to the "boost leak", not all of the measured air mass is filling the cylinders, but enough fuel is being injected for all of the measured air mass, thus the rich air/fuel mixtures.
Now on the other hand, when the turbo is not boosting the intake, the absolute pressure in the intake manifold after the throttle valve, is lower than the ambient atmospheric pressure, and any leak point on the downstream side of the throttle valve, is a "vacuum leak". Now, the air mass entering the engine cylinders is more than the measured air mass, and the ECU injects only enough fuel for the measured air mass, but there is a large fraction of the total air mass that is unmeasured or "False air", so there is not enough fuel mass injected, thus the resulting lean air/fuel mixtures. Capisce?

MarkChai

It was a pronounced sound of air escaping that I could never figure out until I saw that residue.