2016 A3 Hard Start and Misfiring at Idle

Technical Discussions
1

Hey y’all, I have a 2016 A3 Quattro 2.0T. I need to give it gas for it to start, and I have to keep it revving and quickly shift to drive to actually drive it. It drives fine, but if I let it idle, it misfires and throws the EPC and engine light. It’s giving rich fuel trim codes and misfire codes for all cylinders. I just replaced the injectors due to a bad seal on one that was broken and leaking, probably due to high fuel pressure. I monitored fuel pressure live data, and when it started misfiring at idle, the fuel pressure jumped from 45 bar to 60 bar. Thank you!

EDIT: It idles fine on a cold start, but once it’s warm and I drive it, if I stop again, it will misfire.

2

It sounds like you could have a vacuum leak or an issue with the fuel pressure regulator. Since you’re seeing fluctuating fuel pressure, that might be the culprit.

3

Have you checked the spark plugs and coils? Misfires can often be caused by faulty ignition components, especially if it’s misfiring on all cylinders.

4

Since it idles fine when cold, it might be a problem with the engine management system, like a faulty sensor (MAF or O2 sensor). Those can cause rich conditions.

5

You might also want to consider resetting the ECU after replacing parts. Sometimes the ECU needs to relearn after significant repairs.

6

Definitely check for any error codes in the ECU. They can give you more specific guidance on what might be going wrong.