Car: Audi S5 V8 FSI, Direct Injection
I posted a question related to this but might not be the correct issue: Do injectors leak or injector seals leak?
2 months ago (1200 km) I performed a manual carbon clean of the intake ports to remove carbon build up (to get a tiny bit more performance).
I also changed the spark plugs while at it.
To clean the ports, I used Liqui Moly Fuel System Cleaner, which dissolved the carbon build up, and I scrubbed and sucked it away. I didn't removed the fuel rail or injectors, but some of the cleaner/gunk flowed down past the injectors onto the middle of the "V" (which I cleaned up, but some left stuck in injector support)
A few weeks later, after a 30 minute drive + 2 hours leaving the car off, I went to start the car. It cranked a lot more than usual, and limped it's way to starting. Normally it springs to life like any car. I didn't notice the issue again, until...
Last week, the same issue happened again, multiple times, with longer cranking times. Only after a few (1-2) hours. It starts fine cold, and starts back up fine within ~30 mins. I sometimes smell petrol, but not after start up and driven for a bit.
Thermostat was changed 2 years ago.
Scan tool - No fault codes, no dash lights, coolant needle stable at 90C (filtered)
The previous question suggested the ECT sensor. I had a look at the readings of it. The value didn't seem to spike anywhere, and the wires looked OK. I noticed that the value was a bit "slow". From a cold start, at idle, the temp didn't climb above 75C even after 10mins. After a quick drive however, it was around 100C. After a moderate drive, it was around 110C.
Having a browse of the measuring blocks, there was a fuel injection start adaptation. This remained 0% for engine temperature of 25C (cold start), 110C (hot start), 75C (after 1.5 hrs)
Fuel Rail Pressure was around 6 bar when off (25 bar when on, 70+ bar at WOT), it remained this even after 2 hours (I'm guessing it primes when you turn on the ignition)
- Removed 1 spark. When I removed it, I got a whiff of petrol smell. The plug was dry, but looks black. I tried to look inside the cylinder with a torch, and I saw a bit of wetness. I'm not sure if this is normal or not after 1200KM?
Does this sound like an ECT sensor issue, a fuel injector leak, or something else? Obviously changing the ECT sensor is 100x as easy, but if it's not broken I'd rather not touch it.