Air Pump, what does it do besides pumping air into the exhaust?

V12-Engine
1

Yesterday, while re-installing the again repaired alternator, we noticed that a hose to/from the airpump had ripped.

The engine has been having some misfiring and uneven running from cold starts lately.
We exchanged the defective hose and now the engine has the best cold start performance since I don’t know when…purrs like a kitten, no backfiring, no hick-ups and a very impressive roar and power delivery when putting the pedal down.

The makes me curious, because in other air pump related topics, it is stated that the air pump only pumps air into the exhaust for emissions reasons…
Does this pump have a secondary function???

2

Nope, only pumps air into the exhaust and only when the engine is cold. Your misfiring and uneven running must have come from something else, perhaps something you bumped while in there replacing that hose.

3

OK, so the output goes to the exhaust system ONLY. Check…

Is there a vacuum hose that runs towards or in the direct vicinity of the airpump then?
In a V12 it’s quite hard to identify what runs (from) where…

It should be this a hose with a 90 degree bend, screwed onto a piece of metal tubing and a valve system of some kind. After replacing that hose, the engine idles like a charm and pick-up has become quite impressive…

4

There is a valve down there that diverts the air pump output from the exhaust system into the RH air filter housing instead – on the engine side of the air filter. I think it is a vacuum-operated valve. I dunno which way is which on it, but if the air pump continued to pump air into the exhaust after the engine was fully warm, that’d mess things up for sure. Generally, I think the oxygen sensors would detect oxygen due to the pumped air, decide the car is running too lean, and richen it up. That’s primarily a problem once it gets warm, though. After doing this a while, perhaps the spark plugs would get coked up and mess up how it starts and runs cold, I dunno.

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