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marcuswom

S4 will not start, Possible ECU issue?

Ive Recently purchased an S4 which was described as having valve damage. I gave the engine a look over before bidding (with a bore scope) and decided there was no issue with the valves and was just misfiring. I anticipated having to to the timing chain and everything that goes along with it. When I got the car into the work shop I ran the engine and let it get to full temperature. When warm the engine runs without fault. However coming to it the next day it misfired for the first couple of minutes, and then ran fine. I was going to try and replace the oil non return valves as I thought maybe the tensioners were backing of when the engine was left and causing it to run rough untill they pumped out fully.

However, before I got chance to change the parts, I took the car out, stopped it for 10 minutes and tried to start it, it turned over but no fire atall. I tried a diagnostic scan with VCDS and no communication with the ECU was possible, even though I can communicate with all other controllers. The instrument cluster was reporting no communication with the ECU. I checked the J271 current supply relay for the ECU and this seems fine. Ive checked all fuses and power feeds from the ignition switch. Could this be a faulty ECU? The car had been standing for a while and the previous owner said people had been viewing it and jump starting it, and I also jump started it. Has anyone experienced any issues like this before? I would have thought damage would be caused to the ecu immediately after jump starting.

Any information will be gratefully received.

Marcus
James777

Marcus

If you don't get any responses, try Audizine.

James
Mocke

If the time is not an issue - send me your ECU - i will check it for you.
You also have Rick at Unicorn closer to you. He can diagnose faulty ECU for you.
marcuswom

I purchased a second hand ECU which fixed the problem, also fitted a new ECU power supply relay.  Im hoping there isnt an intermittent short in the loom somewhere which caused the damage in the first place.
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