Audi Q8 Engine Problems Point to Failing Injectors

I experienced similar issues with my 2018 Audi Q7 with the petrol engine. Having some experience with engine performance problems, these symptoms immediately pointed to injection system issues. The main problem turned out to be a faulty wiring connection to the fuel injectors. The workshop found that one of the connector plugs had corroded, causing irregular fuel delivery. This explained both the poor performance and increased fuel consumption. The repair was straightforward, they cleaned the connections and replaced the damaged wiring harness connector. Total cost was 95 Euro for parts and labor. The engine performance returned to normal immediately after the fix. Before suggesting more specific solutions, could you share: Current mileage on your Q8, When was the last fuel system service, Any check engine lights or error codes, Type of fuel you typically use, When did these symptoms first appear This information would help determine if your issue is similar to what I encountered or potentially something different in the fuel delivery system.

Current mileage is 184387 KM and I had my last service 3 months ago. After reading your response, I noticed a check engine light appeared yesterday. The engine power seems to drop more significantly during highway driving. The smoke is getting worse, especially during cold starts. I am using premium grade fuel as recommended. These issues started about 2 weeks ago and have been getting progressively worse. Initially thought it was just the air filter but given the power loss and smoke, it seems more serious. The fuel system service was done during the last maintenance check.

Thanks for providing those details. Based on your mileage and symptoms, this seems more serious than my initial connector issue. After my wiring fix, I encountered similar problems again, and it turned out to be a failing high-pressure fuel pump, a common issue at higher mileages. The increasing smoke, especially during cold starts, combined with power loss points to fuel delivery problems under pressure. The engine loses power on highways because thats when the fuel system is under maximum load. In my case, replacing the high-pressure pump resolved the power loss and smoke issues. The repair cost was around 850 Euro including parts and labor. If left unaddressed, it risks damaging other engine components. A quick test the workshop can do is measuring the fuel rail pressure. Low pressure readings would confirm if its the pump failing like in my case. The check engine light likely stores codes related to fuel pressure, which will help pinpoint the exact issue. I would suggest getting this checked soon, as running with insufficient fuel pressure can lead to lean air-fuel mixture and potential engine damage. When my pump was replaced, they also cleaned the entire fuel injection system to remove any debris that might have circulated due to the failing pump.

Being at 184387 KM, I should definitely take your advice about getting this checked soon. Your high-pressure fuel pump situation sounds very similar to what I am experiencing, especially the highway performance issues and cold start smoke. The air-fuel mixture problems you mentioned make a lot of sense given my symptoms. I just booked an appointment for next week to have the engine diagnostics done and fuel rail pressure tested. The maintenance costs you quoted around 850 Euro for the pump replacement give me a good baseline for what to expect. Really hope it is just the pump and not more extensive engine damage from running with these issues for the past couple weeks. Will have them inspect the entire fuel injection system while they are at it, as you suggested about checking for debris. The performance loss during highway driving definitely indicates its time to address this before it gets worse. Thank you for walking through your repair experience, it helped me understand what I am likely dealing with.