So. I have developed another issue with Miss Piggy.

First start of the day all good and driving in normal traffic engine temp is “normal”

If the engine temp rises a little (2-3mm from vertical) engine cuts out and will not start.

Let the pig cool down for a while and she starts right up and drives fine until next time the temp reaches same place.

Coolant has been purged and vacuum filled.

This is driving me nuts.

any ideas?

 

Also to add to this;

The temp does seem quite normal the odd thing here is not the temp fluctuation, it’s the cut out and non restart the I’m interested in.

 

Sounds like there MUST be some stored diagnostic codes. Could be something like a radiator that has enough blockages to reduce cooling capacity. Could be a bad water temp sensor. But any intentional engine shutdown should have a code. If this is happening without a check engine light, that would be strange. Even if there is no CEL, a Porsche diag tool could reveal codes that could identify the problem. Could be worn impellers in the water pump or some kind of thermostat related issue... this is one of those times that it could be nothing but guessing without more info from Durametric or other Porsche-specific diag tool.

I think somebody here had trouble getting air out of the cooling system until they elevated the front of the car enough that the bleeder is the highest point in the cooling system. And turn heater to maximum hot so water is actively flowing through the heater core while you are vacuum bleeding.

 

Thanks for the response.

I don't "think" I have a cooling issue, the gauge (for what it is worth) shows pretty normal behavior as far as I am concerned. The shut down and non start issue occurred basically out of the blue.
Then as part of my climate control debacle (comments in the no heat post here) i decided to flush and re-fill coolant as a while you are in there job.

The shut down and non start issue is still present after a full vacuum bleed and fill, but as mentioned above the cooling system "seems" to be operating correctly.
No CEL before or during the shutdown, shutdown behaves as if car enters a no spark state. Trying to restart the starter engages but car will not start. After a cool down period (approx. 20min) the car will start and drive as if nothing has happened.

I have been using OBDEleven with a modified pin-out quite successfully for the last year, but i don't believe it can access DME. However no codes are stored in the engine module (at least that my mini-homemade-durametric can read)

I am beginning to wonder if this could be the crank position sensor playing up, my reasoning for this is that the cooling system seems to be fine, and the non-start occurs when the whole drive-train is hot.
As i understand it the crank position sensor is located on the trans bell housing which would indeed get quite warm during driving.

I can recreate the issue by driving a short time and then leaving the car parked with engine running (dash temp gauge stays in center more or less) but cut out and non start still occurs.
I was also able to create the same state by "driving the #%&" out of the car in 2nd gear for a bit of snow drift action. This resulted in the same shut down.

Plan of action for today is to use the OBD and monitor both real coolant temp and trans fluid temp, I may also check the bell housing temp with IR thermometer and watch what happens.
I guess I'm looking for some validation to my thinking? Don't feel like playing the throw parts at it and see what sticks game.

Any further inputs from any of the more experienced than I members here are greatly appreciated.

 

After a couple of OBD monitoring sessions you should be able to see at what coolant temp you're getting the shutdown. The gauge in my 09 TTS stays in almost exactly the same place for coolant temps from 180-214 degrees so the gauge isn't really a gauge at all as it's too heavily buffered to be useful. I have a p3cars vent gauge that let's me cycle through different gauge readings, one of which is actual coolant temp and that's the setting I normally leave it on.

Also, see at what actual temp your cooling fans are kicking on, or if they are. If they're not, the car may be shutting itself off since it can't cool itself down. Mine kick on at the 214 number and then the coolant temperature starts falling again.

 

When you unsuccessfully attempt to hot restart, does the tach move at all?

If not, you likely have a bad crank position sensor.

 

The only thing that I can think of that would prevent a trouble code from being stored during the described events is if the DME itself loses power. I suggest that you determine for certain that no trouble codes are stored in the DME.

 

Yea. It seems like Miss Piggy wants to be a 944. Could be the relay 😂

 

Need to double check that next time it happens. Drive today in flowing traffic without issues. Seems to only happen once heat soak sets in.

 

Possibly. The fact that it is so repeatable at a precise temperature is a big clue. Just a hunch, but there could be something screwy going on internally with one of the cooling fan controllers which is reeking havoc with the DME when a certain fan speed is triggered.