1988 audi 5000s quattro random no spark issue
 

hi guys, i have an issue where the car will run fine for a day or so, the engine will suddenly and abruptly die, regardless if the gas pedal is depressed or not.. when it dies it will not start, not even after the engine has cooled overnight.

after it dies, the car will crank but not start. when i checked for spark there is no spark. the DME engine fault code shows no fault.

after about 2 or 3 days (or sometimes longer), it will suddenly start right up and run perfectly fine for another day or so like nothing happened, and then die again.

when it dies, the rpm does not seem to matter as it has died while idling and also died while driving down the freeway at 4000rpm. there is plenty of oil pressure so that is not an issue.

in chasing this issue, the distributor, rotor, wires, plugs, coil, and o2 sensor have all been recently replaced with new components.

i've also recently replaced the coolant thermostat because i had heard it plays a role in determining a/f mixture. no change in behavior and the engine still dies seemingly randomly.

i have since replaced with new components;
1. fuel pump relay
2. fuel filter

i've removed the dme and opened it up to inspect it and could not find any obvious signs of damage, no burnt resistors or leaking capacitors. i haven't thoroughly checked for cold solder joints, but could this be an issue?

any suggestions would be greatly appreciated!

i thought i'd follow up on this. after replacing pretty much everything, the solution was to replace the bosch ignition control module (the computer) which is located on the side of the front passenger footwell.

the car has been running great ever since!