Another SAI related question

[mwood]

First post here, so if I'm doing it wrong, let me know!

I'm a new Boxster owner, having purchased a 2003 986 S a month or so ago. It is a 49k mile car, all records, IMS done 1000 miles ago (PO had done just before extended warranty expired, to enhance resale value). I'm really pleased with the car. As for me, I am a decent parts replacer and set up guy (autocross SCCA at National level, currently running a Van Diemen RF88, and also am finishing a bare-metal up restomod on my '66 Sunbeam Tiger), but get pretty lost with modern electronics and emissions systems.

I started noticing an electric motor sound on start up recently, which through searching this forum (and others) I've determined is the secondary air injection pump. Seems it is getting that higher pitched noise that indicates bearings are either dry or worn. I have also searched and determined that: 1) a Porsche oem part is very expensive 2) you can get a new Bosch replacement part for around $545 3) they are readily available on ebay, used, for anywhere from $100-300. Sound about right?

But, here's the thing...I first noticed the noise last week, when it was lasting approximately 30 seconds or so, before cycling off. Now, this week, while the quality of the noise hasn't changed at all, it seems like it is lasting longer. I don't think it is temperature related, as it lasted just as long when I started up this afternoon, after being parked outside in the sun on a warm day, as it did this morning in the 55 degree garage. In any case, it seems like it is more of a 1 minute plus type deal, now, and I believe it was about half that a few days ago.

So, the question: If the SAI is cycling longer, all other factors being equal, what might that indicate?

My plan is to remove and clean/lubricate, as much as possible. If that doesn't work, let it die, if that's what it is going to do, and then replace. Not sure if that means a used part...anyone have any experience with buying used pumps? But, before I would replace, I'd like to figure out if the pump motor is going south for some other reason, if that makes sense.

Thoughts?

Thanks-Mike

Edited August 28, 2012 by mwood

[Loren]

From the Porsche Tech Book...

"If the engine is started in a temperature range between minus 10.5° C and plus 45° C, the secondary air system is activated for a period of time dependent on the start temperature (min. 50 seconds, max. 179 seconds).

The secondary air system is only activated if the following engine-related operating conditions apply:

• Engine load (TL) between 0.7 rns/rev, and 4.7ms/rev.

• Air mass (ML not greater than 300 kg/h

• Engine speed between 680 rpm and 2,800 rpm

• Altitude adaptation factor greater than 0.76 corresponding to less than 2,400 meters above sea level."

Unless it squeals like a pig or causes a CEL I would let it go until it fails.

[kedf1]

I've been running without the SAI system for years. I pulled the fuse., cleared the codes when they popped up, eventually they stopped popping up at all.

[wvicary]

If the combi valve isn't opening the secondary air pump will run long and the pitch of the pump will be different. The DME will operate the pump to the max time looking for a result from the O2 sensors, if the combi valve doesn't open the O2 sensors don't see mixture change and trigger the check engine light.

It's often a failed vacuum line to the valve that's the issue.

[mwood]

Thanks for all the input and ideas.

The idea of the combi valve is something to consider. If the CEL was on, I'd definitely look into it. Actually, I'd like to, anyhow. What's the best way to do so?

On another 986 board, it was suggested that the SAI may actually run longer in initial start up in mild temps, in comparison to when it is actually cold. This is due to the fuel mixture the engine sees in the colder start environment, which is richer and leads to more uncombusted fuel mixing with the injected air. This would result in the cats firing sooner. It makes sense, to me, and aligns with what has been happening...this week, the morning temps have been warmer and the SAI has run a little longer. Does that make sense?