phild328

I have a 2000 Boxster S with M620 e-accelerator, around 96K miles. It has a problem that when started cold it will cough and sputter until it goes closed loop. I have traced it to be a vacuum leak. I think it actually was a few vacuum leaks. I fixed two, and I have no idea where the third one is. I will try to describe this as best as I can.
Coming off the intake manifold is a plastic y-tube that goes to the air-oil seperator (AOS). If that is disconnected and plugged up at the AOS - perfect running engine, everytime. So it is not a leak in the intake. And it is not a leak in the line in the y not going to AOS. I replaced the AOS, also the bellows below it had slipped off a little - which I say is leak #1. All replaced and nice and tight - pretty much the same running problem - didn't fix it. I blocked off the vacuum line coming out of the side of the AOS - did not affect problem. So the only place left to get the air is from the AOS side and downward connection to the block. Somewhere else lets air into the crankcase and then into the AOS and back into the intake. So I double check the oil filler, which looked good first time - it was actually cracked upon further inscpection. So I replace the oil filler bellow-type tube. This seemed to help a little bit - the problem isn't as bad - but it is still there. Removal of the oil filler cap while running does what it should - small vacuum draw - engine compensates.

So - my actual question is: Where else can there be a vacuum leak?

I have never worked on these types of engines before and I don't know where to look without tearing everything off the engine (I would rather not).
Thanks in advance.

Macster

Had a vacuum leak from the oil filler tube cap. Had me thinking all sorts of things, even caused me to replace MAF. Of course, error codes came back shortly after new MAF installed.

Was really puzzled until co-worker heard the thing leaking one night while I had rear trunk open and engine running. (I'm hard of hearing.)

You can "search" for a vacuum leak with a bottle of propane or whatever the stuff in those blue small pressure tanks is that for instance plumbers use to solder up copper pipe.

With engine idling open valve on tank and aim nozzle at various locations from MAF on down stream towards engine, around the intake manifold. If leak area encountered engine should react by picking up some rpms.

(With engine running, test this by shoving nozzle with valve open into air intake opening and seeing how engine reacts.)

For those hard to get at locations, find length of hose that slips over propane tank nozzle and that you can shove/snake down under manifold. Be careful you don't shove it into serpentine belt drive at front of engine.

Sincerely,

Macster.

rdshon

There are several vacuum lines, valves, and a vacuum reservoir under the intake manifold that can be a source of vacuum leaks. Half of the system is to operate the Air Injection valve, the other half to operate the intake manifold resonance tube valve (which is on the bottom of the forward intake manifold crossover tube). It is easy for one or another of the connections to become disconnected, or for a plastic line to crack somewhere. The reservoir (item #16) can also become leaky, or an electric vacuum control valve (item #18) could fail.

You will need to see a service manual to understand all of the connections, Attached is a diagram of the Air Injection valve control part of the vacuum system. The check valve (item #22) is supposed to plug into a hole in the bottom of the right-front intake manifold connector (the rubber connector with two hose clamps). This is most commonly disconnected item.

depositchoice

I have ran into the same problem with a vacuum line from the manifold where the dealer has discribed that this line has cracked causing further problems along with a valve ultimately leading to the cause of an emergency transmission run. If this does not fix the problem it may be something else ? My 2002 porsche boxster S is a German machine correct ? At 83,000 miles one would figure that the vehicle was practically brand new considering it is a 3.2 w/triptronic. How can this be the case with such a hiccup before dinner is even served ? Tell me its not true cause I dont want to have to skip dinner in search of better food to satisfy my hunger, In other words I dont agree to be fed HAM and told that its sirloin.

depositchoice

Is this problem with the vacuum leak anything more than fantasy ?

Macster

Boxster is made in Finland if it has U in the factory code position of its VIN. If it has an S it is made in Germany.

At 83K miles the car is not brand new, not unless it rolled off the factory floor with 83K miles on it.

At around 80K miles I had replaced on my 02 an RMS (doesn't everyone?), AOS, and not long after 80K miles a rear wheel bearing.

My advice is to locate the cracked hose(s) and replace along with whatever other hardware is acting up -- this valve you mention -- and then enjoy the car.

Celebrate the vacuum/valve repairs by driving the car to a local hamburger joint!

Sincerely,

Macster.

depositchoice

Im not going to waste my time if the car isnt going to last than it isnt worth the embarrassment, I followed my instinct when I purchased, I will definitely go an alternate direction since problems lye in the near future, I would like to speak my mind as this may be my very last post in the porsche forum. " If the new generation of porsche cannot be compared to the race horse that is on the hood than than horse should no longer be part of emblem or crest. The great Ferdinand Porsche did not make these cars to be like all the rest and the fact that another non european car could even compete with porsche with durability curves ones appetite "