5th gear stall, cloud of white smoke

[p88player]

Hello,

I had an incident on the freeway the other day in my 1999 boxster and I have no idea what kind of damage I'm looking at or how to fix it.

I was on the freeway cruising and out of the blue my car stalled out in 5th gear at about 70mph! No awkward sounds, jolting, sputtering, or anything of the sort just immediate stall and a cloud of white smoke. I looked in my rear view and there was TONS of white smoke being poured out from what seemed to be the exhaust, I don't recall smoke exiting the engine vents. Immediately, I pulled over to the shoulder and let my car sit in the off position and it remained smoking. Against my best judgment, I restarted my car a few minutes later and drove an addition 1/4 mile to the nearest exit. Fortunately there was a gas station at the exit to stop at until my tow arrived. When he arrived I started it again to unlock my wheels to align it with the flatbed, this time the smoke continued to slowly creep from the left side of the exhaust for about 5 minutes.

For about a week prior to this, my car would smoke at start up after remaining off for a few hours. I had arranged to meet with a mechanic but needless to say I didn't get to see him before this incident. I will be meeting with him this weekend, however he is now a porsche mechanic so I'm trying to get some addition feedback to get ideas of what the problem could be.

I have about 83000 miles on the car, I'm pretty good about keeping up with the maintenace, and I have not had any other problems with it prior to this. Any ideas, thoughts, comments about my stall and smoke of death?

[1schoir]

Hello,

I had an incident on the freeway the other day in my 1999 boxster and I have no idea what kind of damage I'm looking at or how to fix it.

I was on the freeway cruising and out of the blue my car stalled out in 5th gear at about 70mph! No awkward sounds, jolting, sputtering, or anything of the sort just immediate stall and a cloud of white smoke. I looked in my rear view and there was TONS of white smoke being poured out from what seemed to be the exhaust, I don't recall smoke exiting the engine vents. Immediately, I pulled over to the shoulder and let my car sit in the off position and it remained smoking. Against my best judgment, I restarted my car a few minutes later and drove an addition 1/4 mile to the nearest exit. Fortunately there was a gas station at the exit to stop at until my tow arrived. When he arrived I started it again to unlock my wheels to align it with the flatbed, this time the smoke continued to slowly creep from the left side of the exhaust for about 5 minutes.

For about a week prior to this, my car would smoke at start up after remaining off for a few hours. I had arranged to meet with a mechanic but needless to say I didn't get to see him before this incident. I will be meeting with him this weekend, however he is now a porsche mechanic so I'm trying to get some addition feedback to get ideas of what the problem could be.

I have about 83000 miles on the car, I'm pretty good about keeping up with the maintenace, and I have not had any other problems with it prior to this. Any ideas, thoughts, comments about my stall and smoke of death?

Huge clouds of white smoke often means a failing or failed AOS. See if your '99 still has the old style AOS (you can tell by the orientation of the top circular part of the AOS... horizontal = old version... vertical [i.e., in line with the body of the AOS]= new version). If it does, that increases the likelihood that it is your AOS, a fairly straightforward part to replace.

Take a look at this link, I posted photos of what both of the versions look like: http://www.renntech.org/forums/index.php?s...c=22857&hl=

Also, take a look at Mike Focke's Boxster Pages website for a really nice photo of the type of white smoke condition caused by a failing AOS and for other invaluable information on AOS'.

Regards, Maurice.

[p88player]

Thanks for the hand Maurice! I looked into the site you recommend, very informational in regards to DIY replacement.

So now that I have an idea of what's wrong, I have a couple more questions. If my problem is indeed an AOS issue:

1) How can I tell if the AOS has completely failed?

2) If it has completely failed, would there be additional damage?

3) What kind of additional damage may have been caused?

I would be thrilled if I could solely replace the AOS and get back on the road, however I'm just extra concerned because there was ALOT of smoke in addition to my car stalling while driving.

Thanks again

Gabriel

[Glyn]

Thanks for the hand Maurice! I looked into the site you recommend, very informational in regards to DIY replacement.

So now that I have an idea of what's wrong, I have a couple more questions. If my problem is indeed an AOS issue:

1) How can I tell if the AOS has completely failed?

2) If it has completely failed, would there be additional damage?

3) What kind of additional damage may have been caused?

I would be thrilled if I could solely replace the AOS and get back on the road, however I'm just extra concerned because there was ALOT of smoke in addition to my car stalling while driving.

Thanks again

Gabriel

If its the AOS and it certainly sounds like it then there will be no other problems, the smoke would have been oil burning, just a tad of oil will produce a large amount of smoke.

You were able to restart the engine so no other damage is likely.

You read these forums and you will hear about "Hydrolock" this condition is when a large amount of a liquid (in this case oil) enters the cylinder and the piston rises to compress it - liquids cannot compress so the effect is like an engine siezure only it locks so quickly that it bends the con rod or breaks the piston.

Although i read on these forums that a failed AOS could cause this condition i have never come accros a single case, the J or Y tube that links the AOS to the induction system is a small pipe and i doubt it could carry enough oil to be able to create that condition given the position of the AOS to the sump.

The AOS handles oil mist, it feeds combustion gasses into the induction whilst doing its best to stop the oil mist making it through, when the diaphram valve inside the AOS fails it allows this mist to be inducted - hence the smoke.

If the car starts and sounds fine let it warm up, check the water temperature, if there is a water issue getting into the cylinders you will notice an excessive water temperature (it will boil up), to check if the head gasket has gone remove the water cap and start the engine, air bubles will be produced and the pressure build up from compression will cause the water to overflow the resovoir like a volcano.

If you have none of these issues then simply replace the AOS, a tedious job and will take a few hours but the fitted price by Porsche is about 10 times the cost of the part.

[p88player]

Alright, I've finally gotten around to changing my AOS!

So I actually did more than change the AOS. I also change the spark plugs, oil, oil filter, and air filter. My ride is up and running, however it's not up to 100%. Is it normal for the car to have the following symptoms after the new parts have been installed?

1. Although the white smoke has decreased dramatically, sometimes, there is still a little bit of smoke at start up.

2. In first three gears, the car doesn't pick up to full potential until 3000 rpms.

3. Every once in a while after driving it hard, there seems to be a random hollow pop sound which comes from the bottom left side of the car and can be felt in the pedals.

4. Sometimes when punching the gas the car has a hard time keeping up with the escalating rmps, and for lack of a better description, appears to slightly choke. Not enough to cause the car to stall but enough to keep the rpms from rising quickly

I'm at a loss for ideas. Any clues?

Thank to everyone that has responded :)

[p88player]

Alright, I've finally gotten around to changing my AOS!

So I actually did more than change the AOS. I also change the spark plugs, oil, oil filter, and air filter. My ride is up and running, however it's not up to 100%. Is it normal for the car to have the following symptoms after the new parts have been installed?

1. Although the white smoke has decreased dramatically, sometimes, there is still a little bit of smoke at start up.

2. In first three gears, the car doesn't pick up to full potential until 3000 rpms.

3. Every once in a while after driving it hard, there seems to be a random hollow pop sound which comes from the bottom left side of the car and can be felt in the pedals.

4. Sometimes when punching the gas the car has a hard time keeping up with the escalating rmps, and for lack of a better description, appears to slightly choke. Not enough to cause the car to stall but enough to keep the rpms from rising quickly

I'm at a loss for ideas. Any clues?

Thank to everyone that has responded :)

Just for clarification, the AOS was in fact the main issue. When pulled out the bottom bellows had practically been blown apart from the main body of the AOS. So thank you to everyone who accurately tagged the AOS as the problem to my incident on the freeway.

[topmech0]

Alright, I've finally gotten around to changing my AOS!

So I actually did more than change the AOS. I also change the spark plugs, oil, oil filter, and air filter. My ride is up and running, however it's not up to 100%. Is it normal for the car to have the following symptoms after the new parts have been installed?

1. Although the white smoke has decreased dramatically, sometimes, there is still a little bit of smoke at start up.

2. In first three gears, the car doesn't pick up to full potential until 3000 rpms.

3. Every once in a while after driving it hard, there seems to be a random hollow pop sound which comes from the bottom left side of the car and can be felt in the pedals.

4. Sometimes when punching the gas the car has a hard time keeping up with the escalating rmps, and for lack of a better description, appears to slightly choke. Not enough to cause the car to stall but enough to keep the rpms from rising quickly

I'm at a loss for ideas. Any clues?

Thank to everyone that has responded :)

Just for clarification, the AOS was in fact the main issue. When pulled out the bottom bellows had practically been blown apart from the main body of the AOS. So thank you to everyone who accurately tagged the AOS as the problem to my incident on the freeway.

hi there,good to hear it seems it was AOS and not something more serious. all the other little symptons you now have could be due to the fact when AOS fails it allows oil into intake(hence the smoke on freeway). you should remove and thoroughly clean the throttle body and if you can the intake manifolds of oil. eventually the residual oil still hanging around will clear after time. once you are sure all is clean then look with PST2,PIWIS or durametric and clear any remaining fault codes. give a long road test and recheck for new codes. good luck!

[Glyn]

The new problem you describe sounds very much like the MAF, Try disconnecting the electrical plug on the MAF, then go for a run.

The engine management system will revert to its limited operation strategy (It will guess the air/fuel ratio) The engine management system "Guess" will be better than the faulty reading from a knackered MAF - therefore the car will run better - If this is the case then simply replace the MAF

[mikefocke]

I'd look at the throttle body first

How to

My reasoning is that, since the AOS failed and it is known to contaminate the throttle body, why look at the MAF which is outboard of the J/Y-tube until you have removed all the oil from the air intake system.

[Glyn]

The car struggles to freely rev until over 3000rpm

A slight popping?

I would suspect that a few miles of hard driving would clear any residual oil, once over 3000rpm the car runs fine - so this excludes plugs being fowled and the new AOS will be preventing more oil contamination.

The popping sound - suspect this will be on the overrun and indicative of a weak mixture- mixture is controlled by MAF.

The time taken to remove the electrical plug from the MAF and test the car is substantially lower than the removal of the throttle body - its a simple test, sure - if the disconnection makes no difference then go for the throttle body

Well thats the logic of my thinking