The saga continues (was T44TQ MC2 stumbling)

[Larry C Leung]

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At the moment, I believe that the air temp sensor in the IC
is possibly suspect. The main question is, can the air
temp sensor affect cold starts? If so, how? Does a sensor
that acts as if the air is warm prevent the cold start valve
from firing? What end of the resistance range is considered
cool? Hot? From the Bentley, all I can figure out is that the
range of resistances that are acceptable are from 0 to 700 ohms
with the sensor plugged into the circuit. Measured resistance
of the lines from the sensor to ECU is about 143 ohms.

Symptoms:

Car stumbles on acceleration under load, or struggles under
load intermittently.

Acts like it's either retarded or starved for fuel, SOMETIMES
recovers when backing off of the gas and re-applying, though
this doesn't always help.

Worse at part throttle under boost, though sometimes goes totally
flat even at full throttle.

Worse when the car or air is warm

BUT, won't start when it's cold without pumping the gas, even then
sometimes won't start totally cold if it's cool out.

Gets full boost, and then some, wastegate is shimmed. Stock ECU,
never have hit fuel pump shut-off. ECU can reach a sustained 1.5
bar with an occasional blip of 1.6 on the dash gage.


Background of repari attempts:

So far, have eliminated vacuum leaks as the problem. Used Ether
based starting fluid and even manipulated the rubber parts while
spraying, no effect.

Passes weakly the dipstick test, (stumbles but doesn't stall, stalls
when oil filler cap is lifted.)

Cleaned ISV and Crankcase breather.

1 month old Multifunction sensor, and plug wires.

1 - 2 year old cap, rotor, plugs, visually check well.

New Fuel filter

Freshly cleaned air filter (K&N)

Clean and checked air temp sensor (engine cold) 407 ohms,

                      550 ohms at the ECU

Codes: First two codes - Bad OXY sensor, over-rev
                                                reset -

                                                Run car after new fuel
filter

                                                Air temp sensor

                                                reset

                                                Air temp sensor

Rechecked the air sensor - 550 at the sensor.

So, is the sensor showing enough heat to warrant a ignition retard
or not? looks like if seems to respond to longer runs under boost
with more stumbling, however, traffic doesn't allow a real test of
this.

Any ideas?

Thanks for all of your help.

LL - NY befuddled
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