Ok so I have an 87 s4 and up until about 2 months ago it ran nearly perfect. The issue I'm having is it will start when cold but after it warms up it will die. No noticeable power loss when I can drive it. Feels like ignition is just being switched off.
list of things done

-compression test shows about 120 psi on both rotors
=fuel pump is about 6 months old
-new fuel filter
-plugs and wires are about 3 months old
-new thermo sensor(one on the water pump)
-tested coils with ohm meter 12v and .5 resistance
-air filter cleaned
-oil changed about 1500 miles ago
-changed ALL of the fuses

 

Can you start it back up after it dies or do you have to wait until cold?

 

have to wait till it cools down a bit
it doesn't do this all the time, drove it for 2 weeks after it started without an issue and started doing it again a few days ago

 

bump

 

Known working thermo sensor?

 

brand new

 

When problems occur w/the thermosensor it is usually related to the wiring connection and not the sensor just failing. If you want to check the operation of the sensor then you need to check the reading at the ECU under a cold engine situation and a warm one. Pin 2I of the ECU (Green/White wire). Should read between 2 to 3 volts w/key to on and engine cold and then the voltage reading drops to close to .5 volts when the car has fully warmed up.

 

While you're waiting for it to cool down, test for spark and fuel.
If you're not getting spark, I'd suspect the CAS or its electrical connector failing after warming up.

 

Thanks I'll try that and let you know

 

so still getting spark but not consistently. Haven't check the pin yet on the ecu. uploading a video of it shutting off

 

 

bump

 

any ideas?

 

Video is set to private, so we can't see it.

 

sorry should be up now

 

got a good deal on a re manned CAS. so gonna try that when it gets here

 

Few more questions:
When warm, does it start every time?
When warm, does it run for a consistent amount of time? How long?

I'd expect to see it struggle a little more if it has intermittent ignition.
Moving onto fuel, try jumpering the fuel pump check connector and see if it keeps running.

 

Warm= no start and it does have a miss when its idling. Got another problem now, was removing the old cas and the stud broke off with the nut. No idea how or if I can get it out.

 

OK got the stud out and ordered one from Atkins, anyone know what size nut i need?

 

That stud has a common thread that the 10mm bolts on the car have.
If you grab a bolt with a 10mm head (that was on the car before) then you can use it while you wait for your stud to arrive.
I just used a bolt instead of that stud as I was always scared of losing the nut anyways.

 

OK got the sensor installed (lined up yellow mark on the pulley and the dimple on the sensor) and it won't start. Engine is extremely flooded. Gonna go pick up some mmo and deflood it.

 

MMO did the trick, now just waiting to see if it shuts off again

 

And it died again. Seriously getting frustrated and considering selling it. I love my 7 but I can't figure this out

 

Did you test the water thermosensor as suggested in post #7?

 

First step is to figure out why it is shutting off. It needs spark, gas, and air.

Spark: CAS signal seems ok. Timing was reset. Is it the original hub and timing marks?

Gas: Does it have fuel pressure? The flooding indicates it has pressure and the signal is good.

Air: Do you still have the original thermowax system? Maybe the throttle stop is out of adjustment and isn't allowing in enough air once warmed up. If the throttle cable or dashpots was setting the idle, they may have rattled loose and moved by themselves.
Will it start if you give it throttle?