seedvila

Hi,
Has anyone ever had their engine "de-carbonized"? According to my dad, no one does that any more, yet Porsche instructed our service manager to perform the work under warranty. Thanks, and I'm looking forward to spending some time in the forums. My husband has always been a Porsche fiend and he broke my Porsche "cherry" with a V-6 Cayenne this year. Cheers!

SD Porsche Fan

I'm not sure what is involved in "de-carbonizing". There is a technique that some guys use with 'Sea Foam' where a vacuum line is pulled and you use it to suck in Sea Foam until the motor begins to stumble then you shut it off. Hook everything back up and wait for ten minutes or so then fire it back up. After the smoke clears the motor is supposed to run better as the Sea Foam has disolved carbon deposits. Some say it works great while other say don't do it.

Don't know if that helps or not.

99firehawk

what kind of problems are you having? On occastion we still use decarbs i probaly do 2-3 a year

seedvila

When cold, it takes one or two tries to get it to "catch" and then once it does, the idle is so rough it almost seems as though the car is going to die (was that a long sentence, or what?). It seems we started having the problem once we brought the car up to a higher altitude 3 months ago. We are at 6500 ft up here and I guess there's just not enough air. Down in Reno, we didn't have the same problem given the same conditions. We've maintained it as recommended by Porsche, only run premium unleaded from Chevron or Shell, and drive it at a level that isn't over the top, but won't make you yawn either. We have a 04 Cayenne S also, and have no problems with it all. The dealer attributes the problem to the V-6 engine.

mudman2

A "decoke" is the physical removal of carbon deposits from the valves, ports piston heads and visible cylinder.

I am old !

seedvila

No....just wise

99firehawk

carbon in the pistons could be very detrimental on an engine in that alititue, the carbon effectivly rasies the compression ratio makign the engine more prone to detonation and misfire that the engine fighting at that altitude. I would say try it and see what happens

Budget M3

Sounds like carbon deposits to me...double check the octane of the gas you are using, too. Some mountain regions will only sell you 90 octane (or less) on the premise that at altitude you don't really "need" 91 or higher--even Chevron does this at some mountain locations. While technically true (thinner air requires lower octane to combust efficiently), if you have a full tank of 90 and then take a trip down to lower altitudes (like say, the Bay area) your engine will detonate (e.g. ping) and is prone to carbon buildup until you put the good stuff back in the tank. I use a can of octane boost for those situations, which also has an extra detergent addititive which will keep the injectors clean and resist carbon buildup as well.

Of course, it could also be the poorly programmed (IMHO) auto transmission that allows the engine to "lug" frequently. Although it's good for fuel mileage, you should never allow the V6 engine to turn below 1800 rpm...especially in a higher gear or on a hill. Using the Tip to kick it down and raise the rpms should help prevent recurrence of this problem...

Good luck...let us know how the "treatment" turns out...

seedvila

We have the Cayenne back and sadly, it didn't do any good. If anything, it seems to be running worse (if possible). The recent cold temperatures (it snowed this morning!!!!) seem to just suck the life out of the car, even though it's stored in the garage. The car has never been in the bay area, the only difference in altitude has been from Reno to Tahoe.

I have to agree with Budget M3 about the poor programming. Our Cayenne S hasn't experienced any of the same problems and it has 34,000 miles. Looks like I might be turning the V-6 in for something else...although I would like to hold out for the Panamera.

In the meantime, I will try the advice offered to see if it will help. The dealership told me that basically they can't fix it....only Porsche can with a software update.

hamiam

I had a 1977 Mercury Comet with about 200k and a carb that we did that to when I was a teenager. I HIGHLY doubt that shud ever need to be done to a modern, fuel injected engine. Im not a mechanic but it sounds suspect to me. The computer will adjust to the change in elevation. Is it under warranty? Bring it to a new dealer and/or contact PCNA. This is bullsh-t.

prm1177

It depends on the nature of the fuel injection system. If the fuel is directly injected into the cylinder, this is generally unnecessary. However, some systems (BMW for example) inject the fuel at the valve intake. The deposition of fuel on hot valves can cause a carbon build-up. Don't know if this is what is used in the V6 peppers.

I used to periodically use a BMW recommended German product called Lubro Moly Ventil Sauber in the gas to clear this out. Older engines used to need a "hot soak" where you get the engine to temp, pulled a vacuum hose and placed it into the can of treatment. Pinch the hose, have someone start the engine and gradually regulate the flow by un-pinching the hose, until the last 1/5 of the can was left. You then opened the hose all the way to suck in the remaining treatment. The engine would stall. You reconnected the vacuum hose, and let the engine sit for a bout 45 minutes while the treatment soaked into and loosened the deposits. Restarting was hideous as the exhaust would blow smoke and the engine would run roughly for about 5 miles of driving. The majority of the deposits would be gone, though. Try a can in a tank to see if this clears things up for you. You can order it through Bavarian Autosport or another Internet parts store.

99firehawk

well if i was checking the car..........id be checking for fuel pressure bleed back ......................

seedvila

Put this in layman's terms (or at least so my non-mechanically inclined self can understand!!!)

charlieXS

when I was a teen we used to pour water down the carb on our drag cars to clean up the heads...

weirdest feeling doing it... but it works.

seedvila

Funny you should say that, because when I picked up the car and started it. I heard the strangest gurgling sound from the engine area. I wouldn't be at all surprised if that's what they did and then tried to write it off as a 3 hour process.