3000teeth

Right after I bought mine, I took it to get smogged and the guy told me it probably wouldn't smog and that I'd need $1000s in parts to get it fixed. I took it to a reputable Porche mechanic near me (911 guys - racers) with the failed results, and Brad, the owner made a small adjustment (sorry, still not sure exactly what he did) and it smogged when I took it back --to the smog guys surprise and my chagrin.

Don't buy any parts until you know what the problem is, which is standard advice for anything that goes wrong with these cars, from my experience.

-T

WallyP

First thing to check is the driver's side coil wire...

Canajet

Thanks, everyone...I am working on it!

Canajet

So here is the update...my mechanic says that one cylinder is not working some of the time. Sounds like the 4 cylinder shutdown, but it is only 1 cylinder and has been over 24 hours. He says with only 7 cylinders running, the HC numbers on the smog report would be high. Any ideas what caused/how to fix??
Thanks!

ZEUS+

As Dr Bob mentioned a lean misfire will raise HC. Isolate the problem cyl. and determine the cause. If the plug is not firing at all, co would be higher. No fuel would raise nox. If it was in limp mode 4 injectors would not pulse. Posibble intermittent skip, vacuum leak, dirty injector are a few causes.

3000teeth

You should do one of two things: 1) Get the hell away from this mechanic and get a second and third opinion, or 2) Just cut to the chase and buy him a new boat.

WICruiser

If it is actually one cylinder there are a limited number of suspects. To isolate the cylinder pull all the spark plugs. One should look different than the rest. If is wet you have either a bad plug or a bad wire most likely. If it is very white then you don't have fuel so check the wiring for the injector or the injector itself.

You would only have high HC if the one cylinder that was not firing was due to no spark, causing raw fuel to get into the exhaust. If you have high NOx it is porbably a fuel delivery problem and firing but very lean.

dr bob

With a plug not firing at all, HC goes up but CO and NOx stay the same. CO is a function of combustion quality. NOx is a function of combustion temperatures. No spark means no combustion means no CO and no NOx.

"No Fuel" will not raise NOx, but "Not Enough Fuel" will. A lean condiion on just one cylinder is often enough to push you over the edge. Again, no combustion because of ignition failure means there's not enough heat in the chamber to make NOx. A partially-plugged injector can easliy be a cause; verify your combustion quality by liooking at the plugs. Make sure you have 8 of the same, correct plugs too. The copper plugs seem to do better on NOx, at least in my car.

OrionKhan

I had a car fail before from the wrong plugs installed by a po.

ZEUS+

A washed down cyl. will have increased CO due to oil contamination. No fuel with spark can increase cyl. temp. Always test with good running engine with fresh oil.

Imo000

How about an openly failed thermostat? Can that keep the engine and the combustion chanber too cold and bring the NoX up?

BarryW

One cylinder misfiring could also be caused by a faulty injector.

Bill51sdr

Ummm... NoX is a product of high combustion chamber temps, not cold.

Canajet

Thanks, everyone...here's the answer: It turns out that on CA cars (of course) there are 2 Ignition Monitoring Relays ($300 each), that aren't even in the Porsche wiring diagrams. There is virtually none available in the U.S...have to order them from Stuttgart. One is working, but one is opening and is the cause.
Thanks for your help!!

3000teeth

Still sounds sketchy to to me. Where are these $300 relays located?