I posted previously about this ENGINE CONTROL FAULT issue. When it first appeared, it had no performance related side effects. Eventually, I noticed it was laboring heavily in the lower gears, sputtering, but mostly in reverse, and only occasionally - it was not constant.
Originally, I tried something odd - i filled up with 87 octane and after about 10-20 miles, the fault went away. I finished that tank and did one more just like it. Once that was finished, I refilled with 93 octane. Within 1 day, the ENGINE CONTROL FAULT returned. It sort of feels like a rough idle or maybe slightly retarded timing - like if you were working on a classic car and didn't set the cam so it was rumbling - minus the rumble. Performance wise, the best way i can describe it is if you were driving manual and tried to start in 2nd gear. The issue goes away or is much less noticeable after 3rd gear, 25-30mph. Reversing out of a parking space though was at such a rough idle it almost felt like it was going to stall out but didn't. That got me to thinking - how can I resolve this? The first thing I tested was to use the car in manual mode while at a low speed. It immediately was more responsive and didn't sputter as much. I tried with the paddle shifters and the gear shifter, both methods all but eliminated the rough performance.
I'm curious about OP's fix though. If this were a fuel/air mixture issue, it would present either way, regardless of what shifting mode was in use. Now that I have isolated this to something that is more noticeable in automatic vs paddle mode, It leads me more to think it's a tranny issue, possibly vacuum related or computer related with the shift points. I won't even pretend to guess how all the electronics interact or how to resolve these things. Give me a 350 big block and I will tear it down and put it all back together blindfolded. All the electronic and computerized parts give me a headache.
I had a Land Rover years ago that decided it wouldn't start one day. I turned the key and just got a solenoid click. then hot air started blowing while the AC was on, radio was glitching and screen says Transmission Control failure. The car had good battery voltage and wasn't even able to start or turn over. After exhaustive research it turned out to be a $7 plastic switch that clips onto the brake pedal to turn on the brake lights. Yes a $7 plastic light switch (which I did not even need a screwdriver to replace), took down an entire rover. The vehicle was completely undrive-able. I couldn't even shift into neutral to get it onto a flatbed. It had to be dragged (kicking and screaming) out of my driveway locked in park. LOL. All that tech (and all this Macan tech are great when working, but you can see when even the slightest thing goes wrong, you're SOL.
