'02 C2, 176,000 miles, original engine. Owned 7 years.

About 2 years ago my car started throwing code 0491 (secondary air injection system, IIRC). Had my P car Indy look at it when I had it in for something else. He thought it was the pump, but since the car ran fine and we have no DMV pollution checks to worry about, he thought it would be fine to just let it go for the time being.

It would throw the code occasionally, although under all kinds of circumstances, so I couldn't draw any conclusions. Lately it's happening more often. Car runs flawlessly. Do I need to address this?

 

I had the same problem on my boxster....I thought it was the pump but I tested it using my durametric and it ran so I knew it wasn't that. Ended up being the vacuum lines...cracks in the rubber fittings....replaced them and all good....no more CEL

Won't hurt car other than maybe foul cats is what I heard since fuel will be too rich. Air injection pump just makes sure there is more oxygen in the exhaust so that unburned fuel will burn in the cats....at least that what I have been told.

 

Thanks lowpue!

 

Fix it! These engines don't like "rich"...read bore scoring.

 

Bill, the air injection does not effect the engine....in the first 30sec when the air pump turns on and the engine is cold, engine tends to run rich whether pump is on or not. The injection happens in the exhaust system and not the engine so there is no impact to engine combustion whether the injection works or not. This is purely an emissions thing to burn off gasoline vapors in the cats.

Southern man, the vacuum lines are needed to open up valves to exhaust system so air can be pumped in. Once engine is warm pump turns off and valve closes so exhaust won't backflow into pump and foul it.

Same thing happened on my Mercedes....replaced crack vacuum hose in that case.

Report back on what eventually solves your CEL

 

Lol, I shouldn't get on the forum at 3am before having my coffee!
Now help me understand this, if the SAI vacuum leak gives a false reading, then adding more fuel, does it not wash down the cylinder?

 

I got the same CEL after i accidentally smashed a vacuum hose taking my alternator out. All of the plastic gets brittle with age and its easy to crack a line. Good luck, hopefully the crack is easy to spot

 

Think of it this way....the combustion has already happened...the exhaust leaves the engine with still some unburnt fuel vapors mixed in....it goes to the catalytic converter which are not hot enough so all the vapors don't burn yet because there isn't enough oxygen....so they inject oxygen before the cats so it could burn more fuel and get cats hotter faster so they are full function sooner and lower emissions. Air injection pump is all about cat efficiency and has nothing to do with engine other land the oxysensors detect the problem and CEL. I am no expert but I am pretty sure I have this right....so stop worrying about fuel wash

 

Understood. I haven't done much research on the SAI and how it functions. Isn't the air injected through the intake runner?I now see it feeds into the head. I had this visioned all wrong...More, coffee and reading needed!

I appreciate the quick 101.

 

That is what the forum is for....I learn so much myself here which is why I love it.

 

Good article i found as i got the code last week. I cleared it and it hasnt come back yet.

http://p-car.com/996/diy/sai/mainpage.html

 

That is what I did for awhile but finally because emissions testing forced me to fix.