Secondary Air System problem

[Adam D'Agosto]

Hi.

I've got a 1997 Box. The car is in great shape with just under 40,000 miles. I'm the third owner and just got into it this past June. During this time, the Check Engine light has come on a few times and the codes alway indicate the Secondary Air System fault. My mechanic says its pretty common problem and the best course of action is the replace all the parts of the system as you really cannot diagnosis each part individually. The labor to get in there one part at a time would be nuts. So, he says it will run about $800 to fix it all up.

 

First, I'd like to work on this myself. What do you all suggest and how I should go about doing this? 

 

I have had the codes cleared and the light does not come back on right away, so the thinking is that whatever is tripping the system fault is NOT always at fault. To me this means it is probably not a leak in a line as the fault would/should immediately return after being cleared on the next cold start. In my case, I can go weeks without it coming back on. Sometimes it goes out on its own.

 

What do you think?

 

Thx!!

[Ahsai]

Do you have an OBDII scanner or Durametric that can read the O2 sensor voltage in real-time? If so, you can try some basic diagnostic first. The problem with your symptoms is it could be anything from a sticky changeover valve, bad one-way valve to partially clogged SAI ports, which require removal of the headers to fix.

[JFP in PA]

Two comments:  First, you need to get the actual codes when the car trips the MIL light.  Without the actual codes, you are guessing at what to check out and/or replace.

 

Secondly, your mechanic's comments are very telling, as they sound like someone who just wants to replace everything rather than do some diagnostics.  Unfortunately, too many shops like to throw your wallet at a problem rather than take the time to do it correctly.  You decidedly can test each component in a system, and quite often replacing or repair one item will fix the problem.

[Adam D'Agosto]

Hi.

I do not have a OBDII Reader (yet). I plan on getting one soon.

The codes are P0410 and P1411.

My mechanic says to replace everything because in his experience this is the most effective way to deal with the nagging problem for someone who does not work on cars. It makes sense for those folks to do that. The LAST thing you want to do it bring your car back to the shop to dig into the car again and replace another part in the system only to find out it's not fixed. Then do it all over again in a few months!

 

But for those who do the work themselves and don't mind digging into the guts of the engine a few times a year to find the culprit, replacing the entire system is unreasonable.

But again, if you see it from the prospective of someone running a business...just get it done the first time and NEVER have to fix it again means you're a good mechanic. Dig in multiple times and charge all that labor each time means you a mechanic rapist! Otherwise, you're just a luck mechanic if you guess right the first time.

 

Anyway I know what the codes are, but they are not specific enough to know which is the first part in the system to replace followed by the second, followed by the third...

That's why I'd like your advice on that. Based on what I've described avove, what is the likely first, second, third part to look at replacing?

 

Thanks!!

 

[Ahsai]

Those codes mean the engine (O2 sensors) doesn't see enough fresh air injected. The most common cause is somethng that's commn for both engine banks sch as one of the vacuum valves and change over valve. If you don't plan to diagnose it yourself, at least you can check if the air pump is running for about 1 min upon cold start (sounds like a small portable vacuum). If the pump is running, further diagnostic is needed.

[Ahsai]

Note also since the SAI system is operated by vacuum, the problem can be as simple as vacuum leak such as an unplugged vacuum hose.

 

 

[Adam D'Agosto]

Hi.

 

Yes I would very much like to diagnose this and figure out what to start with.

And yes the air pump does work as expected. That was the first thing my mechanic asked...

 

As for a leak in a hose....my thought was this. If it were a leak in a hose, the problem would always be present. But, after clearing the codes, the Check Engine light will often stay off for weeks at a time. Also, there was a case or two, where the system cleared the code on its own. So, if it were a leaky hose, I'd think that the check engine light would be a permanent fixture on my dash panel. 

This leads me to believe it it related to a sticky valve (or something like that).

 

Thoughts?

 

 

[Ahsai]

Then it could be the changeover valve, the vacuum activated valve and the one-way valve. Also sometimes a leaky vacuum reservoir could also be the culprit. Further diagnosis is needed for sure. I guess you just have to choose between spending money on diagnostic or use a shot gun method and hoping the problem is fixed. I don't know how much labor will be involved tearing into those valves on a Boxster so I can't comment whether it's worth replacing all the components in case another part fails down the road.

[Adam D'Agosto]

Ok. This is at least a good start. Now maybe someone can help me figure out which of those three items you listed have a higher rate of failure or maybe one is easier to get to or maybe one is freak'en expensive....

 

So, can anyone help me determine the best approach to further investigating the following parts of the SAS:  changeover valve, the vacuum activated valve and the one-way valve on a 1997 Boxster.

 

Thanks!!

[Ahsai]

One will have to get to those valves and apply vacuum and/or power to test them to see if one can blow through the valves.

[Ahsai]

Some good info and pics in this thread.