So here's my story, condensed of course, so as to not take too much time getting to the point.

Just bought my A4 about 2 weeks ago, previous owner said he had fixed all mechanical probs he was aware of, which included replacing the secondary air pump. Bought it, got it home, and that pump felt the need to turn on every 3-4 minutes and run for about 15-20 seconds, which didn't really worry me till it did it all night and left me with a dead battery the next day. So I unplugged it so that wouldnt happen again, had it checked out by a mechanic and they said everything came up fine but reset the computer just to be sure and for the last week it worked fine, heard it run when I started the car, heard it stop when I shut it off, thought it was good. Last couple days, its started doing it again and its clicked the cel on, which autozone pulled up the code and sure enough, the code said something about a bad secondary air flow somethinorother so I poked my nose under the hood and found where the pump connected to the airbox and when it clicked on (still with the engine off...) it didnt seem like it was sucking that much air, not even enough to hold a dollar bill firm enough for it to not just fall to the ground, so my questions are:

-Is the lack of suction normal? Do all secondary air pumps not suck very much or are they supposed to draw in air with enough force that a measly dollar bill should stick to the end of the hose without falling to the ground?
-Is it common that this pump doesnt like to stay off long after the engine is turned off?
-Is it more likely than not that even though this is supposedly a 'new' pump, that its defective regardless?
-And finally, I'm considering just doing away with the whole business with this airbox and just sticking a CAI in there, I found a K&N one for 150 bucks online, but looking at some of the mod-lists of the other members here, the carbino one is pretty popular too so 1) any suggestions on which might be the better deal? and 2) how exactly does a CAI work into the computer system? when I was monkeying with the aforementioned air pump business, I noticed two or three locations on the piping from intake to engine that had wires connected to them, with my assumption being that those are sensors of some sort either for O2 or airflow or whatever so when a CAI is installed, do those get bypassed somehow or are they hooked back up to the new piping for the CAI and the computer adjusted so the CEL doesnt register something funky or something like that?

Thanks for all your help,
-Justin

 

A cold air intake doesn't replace the secondary air pump - those are two separate parts. You can get your intake with no worries - it won't cause problems with the car, but it also won't give you much besides a nice induction roar above 4k RPM - on these cars, the OEM airbox is sufficient for flow. However, I'd still recommend it - it'll dress up the engine bay a bit and you won't have to keep buying air filters. As for which one to get - skip the Carbonio unless you have a burning need for the CF box. Since none of these filters make much power, why spend well over $300? You can pick up a basic cone filter with polished intake pipe and couplers for $40-60 and have every bit of the benefit of the Carbonio.

As for the SAP problem, something is definitely wrong. There's no reason for the SAP to turn on when the car is off. I suppose it's possible that you have an electrical gremlin, but my thinking is that the pump's power is tied to the ignition, and that without the key in the car and turned on, the SAP wouldn't get any power anyhow. Maybe not though - I've never looked into it to be sure. Did the previous owner put in a new SAP, or one from a salvage yard or secondhand purchase? If it's used, then all bets are off - there's no way to know for sure that it wasn't defective before being installed.

 

Gotcha, thanks I know the two are separate parts, when I said 'replace the whole deal' I meant just yank it all out, air box, SAP, and whatever else. I guess the question I should have asked along side that was that since the SAP is a separate part, with a CAI you dont need it right? So it could be just taken out and all would be good ya? Next, it sounds like the carbonio is a poor choice so I doubt I'd go with that anyway, but just for reference, what is the CF box you mentioned? I looked on the noob list for it but didnt find anything. Just curious. Also, with the CAI, whether I bought a kit from K&N or whoever or just did like you suggested and bought the cone filter and intake piping, how exactly does it install? Does it just go straight from filter, through pipe to intake manifold or do you have to put some electronic gizmo's between the filter and pipe and whatnot? Isnt there a sensor for the airflow getting to the engine? Or is that and the O2 sensor and whatever else in the intake manifold and its just a straight shot from the filter, through the pipe and into the manifold?

As for the whole issue with the SAP, the previous owner told me he got the car from a local, non-major dealer that bought it from an auction in california. He said the guy at that sold it to him said it didnt have any problems but when he got it inspected for registration, it came up with leaking oil gaskets, this SAP problem and some other stuff and he said he got it all fixed and put the new SAP in just a few days before I bought it from him but I dont remember him specifying whether it was a new OEM authentic audi part or if it was a rebuilt deal or from a junkyard or what so I'm betting its more than likely that it was a lousy pump from the get-go.

 

Nope - you still need the SAP since its function is not specific to the OEM airbox. If you don't live in an emissions-control inspection state, you could dump it. Someone out there has a delete kit for the SAP including a block-off plate and resistor to trick the ECU. I don't recall who it is, but send a message to CincyTT - he knows. If you have emissions though, you'll fail without it.

Carbonio is nice-looking but that's about it. CF = carbon fiber (that's what the box is made of, or at least styled to look like). As for installing the intake, I bought mine off eBay. It has silicone connectors, an air intake cone, and an adapter plate. The whole stock airbox and box piping comes out, and you install it this way: air cone - adapter plate screwed to mass airflow sensor (which is what measures the air coming in - it's already on your car) - silicone connector - chrome intake pipe - silicone connector to inlet of throttle body. Once you have it, it'll be pretty self-explanatory. The O2 sensors are in the exhaust piping, not the intake side, so they have no relevance to the installation.

It could be, but it could also be that the SAP is new, but the hoses hooking it up are old/damaged/rotted/etc. It's worth the time to inspect and/or change them - maybe you'll get rid of your codes that way.

 

Sweet, that was a very dummy proof explanation, just what a noob needs thanks. The one thing that still confuses me with the SAP is where does it plug in to a CAI? If I'm supposed to have it for emissions (I live in Utah, so yes I have to do that test) where exactly does it fit in to a CAI's piping? Cuz from most pix I've seen of engine bays that sport CAIs, I've never seen a little one inch hose leading off the main pipe or off the end of the cone or anything like that. Then again, chances are that the owners of those cars I've seen live in an emissions free state and they've just simply done away with the little bugger and modded the ecu like you said is possible.

As for the hoses being bad, its very possible that that's the case, when I did my little dollar bill test to see how hard it was pulling in air, I noticed that the little hose that hooks into the airbox was quite cracked around the end that plugs into the airbox so I threw some electrical tape around it and the elbow connector that went to the airbox in hopes that that might do something, but that was before the pump concluded that it needed to run when the car is off so I havent had a chance to really test my patchwork cuz it was the same day that I patched it that it started clicking on every 5 minutes again.

Anyhow, thanks again for all the help, I'll take a closer look at the hoses on monday and then maybe see if I can track where the power cord is plugged into for the pump and see if its not connected properly, since in my mind, and as you mentioned, once the key is out it should cut the power to that pump all together so maybe the ground wire isnt connected or something so I'll see if I can track that down and maybe that'll work. Normally I wouldnt bother with it since I'm planning on going through with the CAI but since I live in an emissions control state, I'll have to fix it eventually.

 

Actually the SAP won't plumb into an aftermarket intake, but that's OK - the 1" hose you're talking about is just a reference pipe for it, and plumbing it into the airbox is a way for them to keep it drawing air that won't be full of road debris. The breather filter on the end is a way to protect the SAP once you install the intake on the car. And actually it's kind of a pain to get the SAP out, so probably the ones you've seen still use the SAP, or at least still have it in the car.

I can believe that. You should definitely go to AutoZone and ask them to scan your car. They'll do an ECU scan at no charge, and give you a printout of any codes that are stored. A dealer will charge you a half-hour to an hour labor for doing this, so it's a great opportunity to get a scan done. When they give you the printout, they'll give you the codes and their definitions. However, the definitions are not always accurate, as I found out when I had a bad cam sensor (their definition of the code was that it was some secondary driveability sensor). The codes will be correct though, so you can get them, come home, and use the search feature on the forum here to find the codes and what they represent. Also, if you dig through the forum in recent posts (say, the last week or so), someone else talked about having their pump running off and on all night when the car was shut off, and it was killing his battery. Take a look for that thread and you'll probably get some more info that'll help you. And good call about tracing the vacuum lines and power harness as well, although you may also want to see if there is a relay driving the SAP - possibly it's one that's shorting out and causing the SAP to start up - never hurts to check.

 

So pretty much I'll just have this pump chillin in my engine bay without a purpose and taking up unnecessary space? Also, I'm unsure now of what exactly the function of this pump is. I had originally thought it was supposed to draw more air into the airbox when you start the car to balance the fuel/air ratio for the first few minutes before you start driving, which is why I thought that once I had a CAI I could just take it out because there wouldnt be an air box that needs extra air in it, so does it have a different output location that goes right into the motor or exhaust lines or something and its just tubed into the airbox for cleaner air like you said?

 

Exactly right about the fact that it pumps into the engine (from my recollection). Without it you log "incorrect airflow" faults. The pump will still be fully functional with a CAI. Instead of drawing filtered air from the hot side of the airbox, it'll now draw air from the end of the pipe that used to plumb into the airbox. Most people put a small breather filter on it (the "mini-K&N" looking filters that are sold at Advance Auto Parts for about $9). Just put one of those on, and the pump will now draw air through that instead of through the OEM airbox. Then you're good to go.

 

Well that makes a whole hell of a lot more sense thanks. maybe Ill just stick one of those filters on it before I get the CAI and see if that at least gets rid of my CEL and then when I have more time and more money, see if I cant figure out why the little bugger likes staying on all the time. I found that other thread that you mentioned might contain more info, it hadnt been posted on very much so there wasnt a whole lot of actual problem solving info, but it did give me new ideas about other things that might be causing the problem.