Well, I know that it pumps in air to warm up the cats and such..

But I'm wondering - as far as I can surmise, the airpump works by pulling in air from the intake airbox, and pumps it through the air injection fittings into the manifolds/headers while the car is cold.

What I'm wondering i s- when the car is cold and first starts up, its in open loop, reading values from the O2 sensors, right?

Does the extra air/oxygen that's being pumped into the manifolds mess up the O2's readings, and throw off the a/f ratio (or BLMs i guess) after the car enters closed loop? Or does the PCM compensate for the extra air being injected by the air pump?

I'm wondering this because I pulled off the AIR injection fittings and blocked them off, but the air pump still runs - and I can feel air coming out of the metal crossover tubes that the air injection tubes connect to. They're wide open now.

Would this screw up my pcm's learning, or a/f adjustments? Or is there some bigger idea I'm missing?

 

The oxygen pumped in helps the exhaust system heat up quickly. This gets the O2 sensor working faster, as well as the catalytic converter(s) which both need to reach high temperatures before they become effective.

The O2 sensors are NOT read until they reach operating temperature. One of the reasons a car starts in closed loop is that the O2 sensors are too cool to read the exhaust gases.

The AIR system shuts off entirely once the car goes into closed loop. Once it shuts off, there is no way it can affect the gasses in the exhaust, thus your BLM's, A/F ratios, etc will not be affected.

 

Anytime the engine coolant is above 59 degrees after start-up the PCM enables the AIR pump for about 3-4 min max until the car enters closed loop. As for any effects on the O2s, PCM and a/f adjustments I would say there are none and I doubt the AIR pump would have that much influence on any computer readings. HTH

 

if you unhooked the air from the manifolds you should unplug the pump it is pointless to leave it on there running for no reason.

 

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Nah, the reason I unhooked it was because the air injection tubes were cracked.. got to buy new ones so I can pass smog in april.

Thanks for the quick responses and informative posts, guys.