Engine IAT sensor

IAT sensor

OK - I'm real curious of something...

Common sense says the ECU will add fuel for colder air temps. The density of air increases by 1% for every drop of 5ºC, so theoretically, the ECU would inject 1% more fuel to correspond. I know other factors play into this, but in general.

But....what happens to timing with colder air temps?? Does the ECU advance or retard with colder temps? I've heard both.

I've also heard that the IAT sensor is ignored in closed loop. The ECU uses O2 sensor readings in closed loop to adjust fuel injection and timing and only uses the IAT sensor value if in open loop (warm up and WOT, e.g.). Any ideas??

Late,
Trav

The IAT sensor is part of the MAF sensor and is used for detecting ambient temperature on a cold start, and intake air temperature as the engine heats up the incoming air to determine fuel pulse duration.
Only engine RPM, TPS, ECT, MAF and knock sensor inputs can have an influence on the ignition timing map.