1999Porsche911

What makes you think your car will run with "oil wetted" plugs when cold? Just because your AOS is bad does not mean your plugs are wet with oil when cold. Oil from the AOS is cleaned off the plugs at every firing of the plug so there is no oil on the plug at startup.

Bill Pence

I should point out that I am merely passing on the explanation given by the fellow at the service counter at the dealership; that is apparently their understanding. I'm not making anything up to "sound smart". It may be that there are tiny German gnomes hiding within the engine who get pissed off and refuse to work if the engine is shut down rich. Or evil spirits who must be driven out by starving them of nutrient rich alkanes. Whatever. The suggested fix by the dealer worked, and that is the information that I wanted to convey.

As far as EFI engines being easy to flood due to wet plugs, I have not encountered that situation in 24 years of driving a 944, and done similar short moves many times. Certainly Wankel rotary engines are very prone to the problem, but they hydrolock. The dealer's assertion that the horizontal cylinder arrangement led to a pooling of fuel as opposed to draining down in a slant four or V-8 configuration seems reasonable, and would support either wet plugs or a puddle of fuel to wash the cylinder walls.

The dealers rep said that the next thing they do if they can't clear it by cranking is to pull the plugs and squirt oil into the cylinders, which gets the engine running again. If it were only necessary to dry the plugs, why the oil squirt?

Another commenter (Mr. Macster) claimed that the fuel smell in the exhaust was normal. Sorry, no, you weren't there. The cloud of fuel vapor was profound, far beyond anything I have normally encountered. Regarding fuel scrubbing the cylinder walls, washdown due to too rich running conditions is a not uncommon problem in automobile engines, so a dilution of the oil film would not be unexpected. Whether it is sufficient to alter the compression as to inhibit running, I have no idea.

Take the dealer's comments for what they are worth. He may be misguided as to the cause, but he is certainly correct as to the solution.

1999Porsche911

I was not attacking you but the explaination you were given. The fact is, starting a car and shutting it down after 20 seconds or so and letting it sit, often can cause starting problems. Letting it sit longer or cranking the engine with fuel bypassed will get it going again. Most people never expereince the problem since they rarely, if ever, run the engine in this manner.

This is not to say that everytme you start and stop you engine this way you will have a problem. Many variables go into setting up the non start conditions such as temperature of plugs, strength of spark and how much fuel was dumped into the cylinders along with the temperature and humidity of the air. Remember, after initial startup, there is a substantial amount of moisture in each cylinder which contributes to the occasional problem.

As I said before, your engine will lose no compression whatsoever, regardless of how flooded the cylinders are. Removing plugs and squirting oil in each cylinder would do nothing to correct a flooded cylinder condition.

I suspect the dealer rep has never seen the inside of an engine.

Macster

and into intake system. Oil smoke just billowing from exhaust pipes. First time oil level went down a quart or so cause I was over day or so checking various things, trying various things and ws starting/stopping engine many times, running it for only short periods of time.

2nd time I didn't run the engine any more than a few seconds several times as I was doing some double checks to make sure it was AOS.

Anyhow, this oil inhalation by the engine results in when engine first cranked over even before engine controller enables spark and fuel air flowing through intake will carry this oil into cylinders and foul plugs. If real bad oil can flow/drain down intake into one cylinder (one closest to and on the side of the AOS) and if piston at top of intake stroke when engine first cranked and starts to spin inrushing air will carry this oil into cylinder and then piston will rise on compressioni stroke and if oil volume enough this incompressible oil will cause engine to hydraulic lock with the very real risk of serious engine damage arising from it.

(First AOS I learned this happened to my car's engine -- cause I mentioned it as a concern to the service advisor and as my reason for giving up my attempts to diagnose and he admitted it did happen to my car's engine as tech was -- unbeknownst to me and not at my direction -- performing a compression test *before* replacing AOS. Stupid test anyway, the risk all for naught. With cylinders well oiled thus rendering a compression test meaningless cause with that much oil the engine would have had good compression with no rings installed, the oil alone would have sufficed for at least cranking compression test. When I learned of this and got the bill I strongly objected and service manager removed labor for compression test from repair bill.)

For both AOS failures the AOS failed in cold weather. 1st time 6" or more of snow on the ground and I got car stuck in driveway trying to get it lined up for tow truck operator.

2nd time no snow but cold nonetheless.

Anyhow, engine flooding cause of excessive enrichening at cold start is very hard to believe. Porsche engine designers and other engine designers as well have managed to very accurately fuel gas engines under all sorts of conditions: From dead cold below zero starts to extremely hot starts and under all operating conditions in between.

Case in point: I've driven my car over 214,000+ miles in all kind of weather; in the depths of winter to blasting across the desert in 116F heat and from a few feet below sea level in the central valley of CA to 11,000+ feet in the mountains of CO and it has never missed a beat. Started it obviously in these conditions too.

While I don't make a habit of starting then shutting off engine I do this once in a while when I go to leave for office and get a cell phone call that requires I return to house for something or I just plain forget something. My car has never failed to start except on two occasions: One after I left it parked for over a week with an OBD II code reader plugged and original and dying battery ran down; and more recently when after filling gas tank down Palm Springs way engine failed to start -- no crank not enen a click from starter just dead silence -- several times for no reason I could fathom and then just as I had resigned myself to calling a tow truck and removing car from gas station drive one more attempt and engine fired right up and has ever since. Engine of course hot cause I just pulled off freeway to fill tank after having driven from gas station in central valley to there non stop. This failure to start, temporary thank goodness, I suspect related to an almost worn out clutch interlock switch. I have a new one just haven't installed it yet. (Had to replace brake light switch cause it wore out. Funny what wear items become after one drives one of these cars for several hundred thousand miles.)

Anyhow, you can't expect me to believe these engineers were so baffled by what it takes to properly fuel a cold engine that their solution was to dump so much raw gas into the engine at cold start that engine must not be shut off right away or it may not restart cause of too much unburned gas from this overly rich condition.

In fact, if engine spins but doesn't fire/start problem is not too much gas but not enough or no spark. If upon engine crank/start if engine controller receives implausible signals from a critical sensor is may not turn on fuel or spark. For instance if coolant temperature sensor reports say a real high ambient temperature -- and believe it or not this happens cause once in awhile I see in captured and stored coolant sensor readings readings of 315F (for at least one second and maybe up to 5 seconds) -- engine controller will not turn on injectors. Another possibility is if camshaft sensor fails to provide valid readings engine controller will not know *when* to turn on injectors or when to fire the plugs so it will do neither and engine just spins.

Can be some gas smell cause of some gas remaining in engine after engine stop if just started.

Since in the event of either one above senarios does not affect emissions no error code is recorded and CEL not lit. And condition self corrects until next time, which can be very very infrequent.

Camshaft position sensor malfunctioning? Never have seen this error on my Porsche but would get it once in awhile on another car. Finally went to sensor connector at wiring harness and unplugged sensor and connected it again several time to remove any surface corrosion at connector I suspected was causing problem and after this never got the camshaft position sensor error (or any other error fot that matter) again.

Sincerely,

Macster.