Help !!engine Shuts Down While Driving

[P944GUY]

87 944, the engine is shutting down while driving..just quits flat out..no coughing or sputtering..just flat line off. It usually starts right back up after a few sec. of cranking. It does it twice and then runs fine. sometimes it will take 5 to 10 times of cranking it over to get it started.
1. usually happens on cold start...warming it up seems to make no difference.
2. thought it was my shiny new hood insulation, with the foil on it..coming in contact with top of ignition housing..cut away an area of foil above ignition..still does it
3. replaced the coil with a known good
4. replaced fuel press. reg. with known good
5. all sensors have been replaced within the last 2 years

6. I know for a fact that the cat conv. is shot..pieces of the "bisquit" are shooting out of the exhaust..one piece was as large as a small apple. and the piece was melted.....SO are the other pieces (yes, rattles when I drive) clogging my exhaust..I know that this would make my engine run crappy but all out quit. btw..magnaflow high flow cat conv. only 2 years old. I know that a one point this summer the engine was running to hot (mixture off) it actually melted the black rubber bumper above exhaust outlet. so probablly destroyed converter.

7. could the ignition have been shorting out from the foil on hood insulation and ruined the rotor..I know theres a capacitor in there (rotor) .

8. could it be the electrical portion of the ignition switch..I had a chevy truck that did the same thing years ago..and it ended up being the ingition swithc in the steering column...did the same thing..engine would shut off while driving

9. Help !!!!

[Britwrench]

So, when was the last maintenance carried out? If ignition parts have not been properly inspected and replaced if necessary at that time, then the car should have that done first. How old is the fuel pump relay? If more that five years old replace it as relay failure is the most common causes of sudden engine stoppage. Relay should be in stock at your local Porsche dealership or independent repair shop.

[P944GUY]

I have switched out the fuel pump relay with a known good one...still does it

[Britwrench]

I would pull the computer out and see if there are any signs of water contamination caused by the battery tray leaking rain straight onto botht he computer and the alarm relay. Without proper diagnosis this is one of those problems that takes a while to solve. You need to know exactly what is loosing power..could be numerous items such as the fuel pump, computer, crank sensors etc.... Are you absolutely sure the swapped fuel pump relay is good?

[P944GUY]

I'll inspect for water contamination because my problem started when we got some heavy rain and my car sat in a parking lot for a few days..I just started using the car as my daily driver..and it never really sat out in the rain before

[P944GUY]

nope no sign of water. pulled off panel and inspected no signs of water

[P944GUY]

just got back from muffler shop....nothing left of inside of cat..and nothing restricting flow