MrFalcon

I have an Porsche 944 1986 model and when I drive or stand idle it sometimes randomly just dies. When trying to start again most times it works but sometimes it doesn't start again.
The engine start problem was already there before the engine dying started to happen(I am pretty sure its an cable cut/crimp, English is not my native language)
I am trying to find the root cause for the engine dying but there can be so much wrong that I don't even know where to start.

Maybe some extra information idk if its useful,
Sometimes when driving and the engine dies the engine starts it self up again because of the engine still turning however sometimes it also doesn't and I am left with an very silent car on the highway trying to get it to the side-line.

bonus12

DME Relay.
These become faulty over time. Car is easier to start once it cools down. You can test yours by using an easy method called jumping the relay. New ones are around $25.

MrFalcon

Do you think that's the answer for both the problems?
Also what relay aren't there multiple in the car?
Also I forgot to add but around 5k rpm the engine misfires and stays steady at that rpm while misfiring and stuff.

Edit: After some reading i read that the main dme relay controls the fuel pomp too however my Porsche 944 has a fire switch (its an certified cup race car) so the fuel pump actually pumps when starting the engine even when the start motor isn't spinning to start the motor

Jfrahm

Well the DME relay failing is very common and controls the DME (ECU or brain) as well as the fuel pump.
No point in speculating, look at the relay you have and see if it's the known-bad part number and also make a DME relay jumper for testing.

https://www.clarks-garage.com/shop-manual/fuel-05.htm

If you have the problem with the jumper wire in place then we move on to other potential issues.
the 5K problem might be cap, rotor, plug wires. Basic stuff.
-Joel.

MrFalcon

Okay tested the new DME relay didnt fix anything well only the fact that the old DME was not fully in we think. Because the car runs very smooth now but before we didn't even notice it.

But the main problems (engine dying, start motor not always working especially when a lot of power is being drawn(lights and charger) and the misfire at 5k)

jeyjey

This might suggest an issue with your engine ground strap....

Zirconocene

@jeyjey : Or grounds, in general.

The Clark's Garage troubleshooting information is very helpful for these kinds of things, as is checking all the grounds in the car.

Good luck

Jfrahm

I didn't know you had a no-crank issue vs. a cranks-but-no-start
Yes, bad or loose battery cable, cable ends, engine ground... Load test the battery also.