smog

[Erik the Awful]

@Travis Bowser, please proofread what you write before you post it and use punctuation. You'll get better help if we can understand you easily.

The air pump robs almost zero horsepower. Leave it alone unless it's broken.

 

[Schurkey]

It never occurred to me that the computer programming for my '88 with AIR might be run extra-rich at startup when the AIR pump is actively pushing air into the exhaust manifolds instead of blowing in the air cleaner.

I just assumed that it's going to be a bit rich based on the low coolant temp, without being even more rich because of the AIR.

One of our resident computer-tuning experts could probably answer this definitively. Until then, I'd say that unless there's an actual problem with the AIR system, leave it functional.

My AIR pump died at somewhere over 300,000 miles. I had no indication of problem with the AIR pump when the head gasket popped, but the pump was locked-up when I went to install it on the replacement engine a couple months later. 'Course, I had another AIR pump from another core engine that went on in it's place. There's not much to an AIR pump. I'm sure I could fix my broken one with a couple of bearings; all I have to do is figure out what size they are and get replacements.

 

[BeXtreme]

It won't run any richer with or without the pump. Pumping air into the exhaust has zero effect on AFR inside the engine.

It never occurred to me that the computer programming for my '88 with AIR might be run extra-rich at startup when the AIR pump is actively pushing air into the exhaust manifolds instead of blowing in the air cleaner.

I just assumed that it's going to be a bit rich based on the low coolant temp, without being even more rich because of the AIR.

One of our resident computer-tuning experts could probably answer this definitively. Until then, I'd say that unless there's an actual problem with the AIR system, leave it functional.

My AIR pump died at somewhere over 300,000 miles. I had no indication of problem with the AIR pump when the head gasket popped, but the pump was locked-up when I went to install it on the replacement engine a couple months later. 'Course, I had another AIR pump from another core engine that went on in it's place. There's not much to an AIR pump. I'm sure I could fix my broken one with a couple of bearings; all I have to do is figure out what size they are and get replacements.

So... if AIR only functions during warm up, when the O2 sensor isn't affecting fueling at all and it's just running off the tables for CTS fueling, then you would be dumping a bunch of unburnt fuel into your CAT without the AIR system working.

 

[PlayingWithTBI]

if AIR only functions during warm up, when the O2 sensor isn't affecting fueling at all and it's just running off the tables for CTS fueling, then you would be dumping a bunch of unburnt fuel into your CAT without the AIR system working.

I would think the pump is making it leaner so it fires the Cat, heating it up faster, by adding Oxygen. The fuel is already burned in the combustion chamber.

 

[Supercharged111]

So... if AIR only functions during warm up, when the O2 sensor isn't affecting fueling at all and it's just running off the tables for CTS fueling, then you would be dumping a bunch of unburnt fuel into your CAT without the AIR system working.

Correct

I would think the pump is making it leaner so it fires the Cat, heating it up faster, by adding Oxygen. The fuel is already burned in the combustion chamber.

There IS unburned fuel leaving the engine, this is mixed with fresh air from the pump to fire off the cat. Removing the pump and/or cat will not affect AFRs in the engine.

 

[Schurkey]

So... if AIR only functions during warm up, when the O2 sensor isn't affecting fueling at all and it's just running off the tables for CTS fueling, then you would be dumping a bunch of unburnt fuel into your CAT without the AIR system working.

Not dumping MORE unburnt fuel, but pumping LESS air--oxygen--into the exhaust. AIR promotes the burning of that fuel in the exhaust manifold and down-pipe (Y-pipe), this "super-heats" the exhaust flow, which helps heat the catalyst to get it functioning quicker. By burning the fuel in the exhaust system, tailpipe emissions are also reduced at startup.

Without AIR, the "startup" emissions would be higher--enough that in some locations (California and others) they put an AIR pump on the engine to bring the startup emissions down. But in other locations where the looser, "Federal" emissions are in effect, they don't bother.

Far as I know, my truck was originally sold in a "Federal" emissions state. Maybe the county it was sold in has stricter regulations than the rest of the state.