1 Fault Code found - Secondary Air Injection System - PO411 - 35 NEED HELP

being from a world of Minis though, it does make sense, at least in the "hey, let's reduce emissions by diluting the exhaust with clean air, it's not cheating at all because the exhaust gas analyser says so" world of WTF'ness


from '76 they had a thing we call the "smog pump", the head has a fitting in the front for each exhaust valve chamber and a pipe that connects them to a fanbelt driven air pump - it just pumps clean air into the exhaust - apparently to "promote the burning of any raw fuel in the exhaust", but we know the truth on that one - if it ain't gonna burn at 2000° in the chamber, it ain't gonna burn in the exhaust...

filtered air goes to the pump, is pumped out to the top of the combi tower. When the solenoid atop the cam cover gets its signal (eg cold start) it will activate allowing plenum vacuum to suck the combi valve open. The SAI pumped air then flows through this combi valve, down the stack and takes a right angle turn at the base of the stack. From what I understand there's a long horizontal port that links all the exhaust ports. The pump will artificially lean out the mixture prior to the cat. The o2 sensor will see this lean air at start up and this way knows that the pump is running. If you get the CEL its because the ECU knows its running the pump but isn't seeing the desired effect. The aim of the lean mixture is to turn the cat converter into a fan forced furnace and bring it up to operating temperature asap so that precious seconds of potential climate saving cat converting aren't wasted. It should run for about 20 seconds from memory. Basically the engine can run as rich as it needs to or run what timing it needs to (mixtures etc that may not be favourable to the cat) to get a nice clean start and idle, whithout the exhaust gases being too noxious.

Quote:

---

Originally Posted by h100vw

Bad pump Al. ket me know if it comes back. I'll sort it out for you.

Gavin

---

I have to confess Gav, that about a month ago, Sue had been telling me about a new high pitched noise coming for the direction of the SAI. Yes i could not hear it and Sue said it was there at cold start only and went away after a minute so I ignored it. Until the recent CEL.

Gav, what do you suggest is best practice solution to sort hmm, 'fix' the SAI issue?

Cheers Al

Quote:

---

Originally Posted by sambb

The SAI pumped air then flows through this combi valve, down the stack and takes a right angle turn at the base of the stack.

---

see, that's what I expected, so why do people talk about losing water when taking the combi off? where does it come from?

Two choice Al, replace the pump and probably the combi valve too. Or get a tune to fix it. If you're stage 2, I forget, then it's easy for me to arrange that.

If you go stage 2 you usually get the SAI coded out which means you can get rid of the pump and all its gear. You can remove the combi valve itself from on top of the tower and put a blanking plate there or you can pull out the airbox and a few other things to gain access to where the tower bolts onto the side of the head. The latter makes things a lot neater. Trouble is one of the bolts is directly behind a coolant pipe junction. You don't actually have to loose water. You can slide the spring clip hose clamp out of the way and then pull the coolant hose back and park it just before it springs a leak. With the long end of a ball end allen key (and a tube over the short end) you should then be able to get the bolt off to remove the combi tower and then fit a forge blanking plate or the like to cover over the port. First time around I used an ebay cheapy that claimed to have a viton seal. I was lucky I caught it in time but when I went to steal bits off the old cars engine to transfer onto my new engine, I found that the 'viton' o-ring had mostly melted and was on the brink of being sucked into the exhaust. If it'd gotten thru to the turbine that could have been a drama. I just refit the same plate with the steel gasket off the old tower instead and have had the opportunity to check it a few times and it isn't leaking.
If you find that you do have to pull the hose, leave the coolant bottle cap on and clamp the hose and you shouldn't loose much.

Quote:

---

Originally Posted by h100vw

Two choice Al, replace the pump and probably the combi valve too. Or get a tune to fix it. If you're stage 2, I forget, then it's easy for me to arrange that.

---

Hi Gav, thanks advice and for the offer. I still have the Revo tune on mine that it came with. I knew that you can tune it out but can you sort Revo? Cheers Al

Hi Sam, thanks for your shared SAI experience and a seriously well thought out tutorial on the SAI. Appreciate your efforts to assist. They are not in vain! Well done.

Won't be able to do anything with the Revo

Quote:

---

Originally Posted by h100vw

Won't be able to do anything with the Revo

---

Hi Gav, you told me that when you were here, just hoping there was a way.

Plan B what ever that is? Will be a considered and well thought out. Doh!

Give me your best offer for tune options, Gav?

Cheers Al

Quote:

---

Originally Posted by simon k

see, that's what I expected, so why do people talk about losing water when taking the combi off? where does it come from?

---

http://www.vwwatercooled.com.au/foru...tml#post557120

Combi valve has coolant behind it on the head. It's been a few years and i must admit i don't remember much more than that though!