Quote:
Originally Posted by boinkus44
Great news !
I got a call this morning from the dealership (Pfaff Porsche), and the CS is fixed and ready to go. The root cause - mass airflow sensor failure. I couldn't speak with the service tech, so I don't have the full story yet (i.e., how/why the sensor failed), but it seems that mass airflow sensor failed, causing the ECU to "shut down". Somehow this caused the KABOOM which blew the intake plenum (IPD) hose off. Still puzzled about the mechanical clattering that was evident when the car did start after the KABOOM. When I asked specifically about this, I was told that "that is what the motor sounds like with a failed mass airflow sensor and the intake plenum hose disconnected". They did note that the KABOOM may have seemed amplified because I have GT3 seats bolted directly to the floor.
Picked up the CS a couple of hours ago, and it runs perfectly. 100% covered under warranty, no issues in that regard even with the mods and the heavy tracking. The only question they asked me is if I was going to the May 22 track day they are organizing at Mosport. Sounds like a good idea.
Bottom line, even though the symptons of the sensor failure were severe, I've been assured there is "abolutely nothing wrong with the motor". And they did check for over revs, but there was no issue there. All in all, great service and I am kind of shocked (maybe a little embarassed) that something that appeared so severe, turned out be relatively minor. I am going to speak directly with the service tech on Tuesday, so I should have some more detail and insight to add to the story.
In the meantime, anyone else experienced a mass airflow sensor failure ? If so, what were the symptoms ? |
Phew. Glad it was something minor. I'm embarrased for assuming the worst.
Question for you. Are you using the stock gauz air filter, or have you switched to a oil based rechargable filter? Also, have you desnorked?
The Cayman uses a hot film mass air flow sensor. The way it works is, a current is passed through a conductive film that is stretched accross the air intake pipe. The current flow heats the film/wire. As it heats up, it's resistance increases so the current draw drops. As air flows across the wire/film, it cools it which decreases it's resistance and causes it to draw more current. By watching the amount of current the film is drawing, the DME can accurately estimate how much air is flowing past it.
The function of the mass flow sensor is to tell the computer how much air is flowing into the engine. It uses this information to determine how much fuel to inject to match the air flow. So, if it malfunctions, it is very possible that the DME will dump way too much fuel into the engine. More than can be burnt. If basically floods the engine, and this can lead to a backfire.
What causes these sensors to fail? A few things can.
- Water in the intake air (this can only happen if you desnork)
- If you use an oil based filter and over oil it, oil spray can get on the film which will cause it to fail.
- An extreme backfire can destroy the film.
So, you have a chicken/egg scenario. You'll won't know if the failed MAF sensor caused the backfire, or if the backfire cause the failure of the MAF sensor. In time you will. If it does this again, I'd say the backfire was caused by something else and it killed the MF sensor.
Go drive your car, and enjoy.
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