Re: Unless the buildup is really extraordinary and with no other symptoms....

Hi all, I have a 2002 base, manual trasmission with 68,972 miles. I have owned this care for five years and have had very few problems. Just the usual with headlight and ignition switch replacement, I have changed my own oil every three thousand miles. I have noticed a build up on my tailpipe since my last oil change about 1500 miles ago. Recently it has blown smoke on start up a bit more frequently than I have noticed in the past. I did some research and am thinking it is the AOS, however when I remove the oil cap at idle it comes off easily. Any suggestions would be helpful. Thanks.

... trick does is only for a completely blown diaphragm on the AOS.
When they start to go it's a small variation which will progressively get worse with time.
If you're seeing much more soot on the tail pipe and smoke on startup, change the AOS.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

the build up is probably nothing to worry about. Like I like to say: Soot happens. (Cracks me up to say this out loud...)

Anyhow, there are 2 converters between the cylinders of each bank and the exhaust tips. Anything at the tips other than oil or coolant dripping from one or both is more a reflection of how the converters are doing rather than on what's gong on in the chambers.

Just a shot in the dark: Have you changed your driving style? Have you switched brands of gasoline? Do you run the oil level too high, overfilled (above the MAX line)?

All or any combination of one of the above can affect to some extent how the exhaust tips look. But even after sometimes 2 to 3 hundred miles of non-stop driving when I pull one of my car's into a gas station to fill up the gas tank the exhaust tips have some soot build up. Well, not build up per se just a good coating. The coating is thinner than it looks. Once in a great while when no one is looking I'll run a finger tip through the stuff and its just a thin layer of soot. About the only time I've read the tips change their appearance is from track driving. Then the owners worry about that...

Still, pay attention to the engine how it runs.It could be the early warning signs of an AOS. Real early. Or it could be normal. Regardless, like Pedro points out the oil filler tube cap "test" is not always going to have the cap stuck down tight on the tube even if the AOS proves to be bad.

But your car has the pre-conditions for a bad AOS. It has one. You are using the car. Oh, you want me to be more specific? Ok, your car has 68,972 miles. That's the miles at which they have been known to fail. Also at 68,973 miles, 68,974 miles, and well, you get the idea. The AOS can go bad at anytime.

Soot happens.

Soot happens.

Hahahaha.

I needed a laugh.

Thanks Marc, I laughed too. The build up is thick, not soot, and only on top of the exhaust tip. No to overfilling the oil, it generally is right on the mark or just one level below. I did have to add approx a quarter quart last weekend. Will keep checking and tear apart throttle body this weekend to see if it is dirty or has any oil deposits. Yes I have been very fortunate the past 30,000 miles with just routine maint, tires, brake pads, etc. I look at this as a challenge to diagnose and repair, that is a bit of the fun of owing this car.