mwood

First post, here, for me...new Boxster owner, having picked up a 49k mile, 2003 986 S a month or so ago. I'm pretty much infatuated with the car, most fun I've had with a daily driver since I sold my Z06.

I've already joined PCA, mostly to gain access to the great autocross site the GG region has at Alameda (although I'm sure I'll find lots to like about the club). Autocross/Solo is what I do for motorsport, right now, after starting with road racing (initially motorcycles when young and crazy), then open track and then moving to Solo...yes, that sequence is backwards, but that's how it has gone! I run primarily SCCA events and have won class a good number of times at SCCA Tours and Pros, but have only made it "into the trophies" at Nationals. I currently am running a Van Diemen RF88 Formula Ford in the C Modified class.

Besides the autocrossing, I also am finishiing a bare-metal up "restomod" on my 1966 Sunbeam Tiger...looks stock, but running updated drivetrain (302 roller cam motor and 5spd, modified suspension) and no cutting, so it can be returned to stock if ever desired.

So, that's me. I should also add that while I'm a pretty good parts replacer and can set up a car, I'm not so good with the more complex systems on newer cars...particularly the electronics and emissions stuff.

Now, my questions...

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: a) a Porsche oem part is very expensive b) you can get a new Bosch replacement part for around $545 c) 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 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?

And sorry for the very long post

Macster

The SAI pump is triggered by an engine start with the engine temp (make this the coolant temp and the air temp) below a certain threshold.

I can't put my hands on this number right now.

Suffice it to say that in warmer weather the thing may not come on. It won't come on at warm or hot engine start, at least I've never heard it come on these times.

But with cooler weather it will come on. And recently we have had a spell of this in this area.

Out in Livermore I hear the one in my 02 Boxster come on at the 1st start of the engine after the car sits outside overnight.

How long the SAI pump runs is also temp related.

I do not know the details and its seems illogical but I can tell you that milder temps can result in the thing running longer than it would at even colder temps.

I believe this happens because in mild temps the DME doesn't have to enrichen the engine air/fuel mixture as much with the result there is less unburned gasoline to combine with the air provided by the SAI pump to burn a and speed up the warming up of the converters. So the SAI pump runs longer until the O2 sensors after the converters signal things are hot enough.

(About the time the SAI pump shuts off the DME goes closed loop which means the sensors and the converters have to be up to operating temperature.)

In colder weather, the DME has to add more fuel to the air/fuel mixture and this provides more excess fuel in the exhaust which generates more heat ias it is burned in the exhaust/converters and warms up the converters much quicker.

It does seem a little strange -- it did to me at first anyhow -- but once I got familiar with the SAI system at least when the pump came on how long it ran and developed a sense of this run time based on temp I really pay it little mind.

What I do is listen for the pump to come on -- that it comes on when experience tells me it ought to -- and listen to how it sounds -- that it sounds ok and the same as it always has -- and that it goes off after what my seat of the pants SAI tester tells me is a reasonable amount of time. Not too soon, but too late either.

The system has performed flawlessly since Jan 02 and for now over 258K miles.

In your car's case, absent any error codes and absent the thing making any scary noises I'd hazard a guess your car's SAI is just fine.

But I'm not at the car and I can't hear the thing.

So you might want to get a 2nd opinion and from a professional tech. I can't really recommend any indy shops not having any direct experience with any of them, but there are a number of Porsche dealers around, with which I have had experience with regarding their service departments.

There is a Porsche dealer in Walnut Creek, one down in Fremont, another over in Burlingame, one down in Redwood City, yet another dealer in Santa Clara, and last but not least one near me out in Livermore. (There's one in the north bay too, but the city in which it is located escapes me -- and I've never used the dealer's service department.)

Anyone of these would probably give the thing a listen, but of course you'd have to set this up and leave the car overnight outside so the tech would have the benefit of being able to start the engine dead cold and hear the SAI pump run.

Sincerely,

Macster.

mwood

Thanks, Macster, that is very helpful information. I appreciate your taking the time to respond.

The duration of the pump running being kind of inverse to temp (may run longer on slightly warmer days) hits the nail on the head, as it has been a little warmer mornings this week. I still am thinking there has been a definite change in the quality of the sound (louder) over the month I've owned the car, so the concern with the pump's bearings may, unfortunately, be real. I will just have to monitor!

btw, we're kind of neighbors, as I'm just up the road in Alamo. The car has been in Alamo since day one, as I bought it from the original owner, a dentist who lived near us.

Macster

Temperature plays a role in how a car sounds.

In warmer temps my Boxster sounds quite different than it does in colder temps. In the coldest temps the thing sounds well, old.

Sure, it is old, 10 years old and has covered plenty of miles.

But in warmer weather the thing sounds new again.

I'm not talking so much about the engine's sounds, but the car's sounds.

In colder temps fits are tighter and rubbers seals and such are firmer and noise and vibration is just transmitted better. Hence the car has more audio going on.

When warmer things do not fit as tight and the seals and such are much more pliable and better able to dampen vibration and noise.

A lot of words leading up for me to say that the differences in noise you are hearing may be due to simple temperature changes that change the audio signature of the car and in this specific case that of the noise generated/transmitted by the SAI pump.

But I'm not at the car. If you are concerned then all I can suggest is you get a professional mechanic's opinion. Even though there is no CEL and nothing obviously amiss -- ignoring the possibility the noise is an obvious sign something's amiss -- the flip side is the possibility the noise may be an obvious sign (to an experienced mechanic listening to it) something's amiss or on its way to being amiss.

Sincerely,

Macster.

mwood

I should have been more clear. I was referring to "louder" only in regards to the SAI pump, not the car in general. I've listened to the various sound clips on the web of the SAI pump and I'm certain that's is the noise I'm hearing on start up. Given no CEL, a run time right in the expected range (30-45 seconds) and the fact that an outright failure of the pump has no impact on the engine's performance or other components, I'm planning on just leaving it alone, for now. Make sense?