We are original owners of a 2014 SQ5 Prestige, now approaching the 90k-mile mark.

We are experiencing a very interesting issue. EPC light comes on at the same geographic location, and has only ever come on at this location. It’s doesn’t always come on every single time we transit this spot, but about every 3rd to 4th time we do. It’s accompanied by rough/diminished power. Each time, I immediately pull over and turn the ignition off. But I can then restart, with no issue, and resume driving. The first time this occurred was at about 60k miles. Immediately took it into dealer service, and they said error code(s) indicated an ignition fault on #1 cylinder, but they couldn’t identify the exact issue at the time. I was very impressed with the tech’s troubleshooting remedy as instead of just replacing parts, he switched the #1 spark plug with #2, then #1 coil/wire with #3. He left the injectors alone, and told me to drive it for a while, until it happened again. I drove for several k miles without a problem. It took me a few times until I realized this only occurs at the exact same location. OBD code still indicates same issue, which might imply injector, but why only in 1 geographic location. And I’m not talking about within a mile, or even 1/4 mile, but the exact spot. Again, I pull over, stop and restart with no issue and can drive again for several k-miles. And this also only occurs while ascending the mountain, not descending.
This might imply a subtle temperature issue, or perhaps an altitude/pressure sensitivity. Or maybe, as far-fetched as it sounds, outside electrical interference. Was wondering if anyone has experienced anything remotely close to this. I’ve lurked here and in other Audi-related forums but have not come across anything like this.

Thanks in advance!

Bob

 

EPC is electronic power control. You really need to try and scan for codes with VCDS or such immediately after the error pops, before turning off the engine (which many EPC type codes clear automatically at engine off or at engine start). Misfires on cyl1, that was the DTC they found? "EPC light" is as informative as "MIL light", not really until you scan and get the actual error text. Ascending, so under heavier than normal load. Do you notice any difference when you pass through in D vs S? Depending on speed, S might be in a lower gear so higher rpm, different profile. I assume it pops at some point into the ascension, not right at the start of the uphill? You don't encounter a similar uphill in any other locality to counter test it just being the incline load at that speed?

 

Bob:
Welcome to AudiWorld, the best site for Audi enthusiasts.
I am guessing you are having this trouble when pulling hard as up a steep incline? After looking at what the mechanic did, I also think it is in the ignition.
He changed around a plug and a wire, but I suspect a weak coil on number one, if that was not tested. I had a car once that ran just fine, but only did this when really working the engine up a steep hill, it did not give a trouble code or light but a misfire I could feel. Mine was a 2002 Ford Thunderbird with the V-8.
It turned out to be a bad coil. As you know todays engines have a coil firing the plug at each cylinder. I replaced all 8 coils and the plugs myself, and that cured it, I did not find out which one did it. Ford parts were not that expensive, and I have the ability to work on my cars.
I would replace that #1 coil. You are at the point you should replace all the spark plugs at 90K. Good luck, and let us know