XC90 Flashing check engine light after turbo replacement
I'm stumped at an issue I'm experiencing on my 2006 XC90. The turbo in my 2.5T petrol was leaking loads of oil, so I had my local mechanic replace it with a refurbished unit from Reflex Automotive. Straight after I got it back, I started getting a flashing check engine light, but only if I am coasting down a hill. Doesn't do it under load, just sometimes when I crested a hill and was coasting down the other side. Also seemed to only happen when warm, never straight after engine start. The flashing light would last about 7-10 blinks. Sometimes the check engine light would set after flashing, sometimes not. The codes would be random misfires or a misfire for a particular cylinder, but not always the same cylinder. This makes me think it's a sensor like the knock sensor, but the mechanic was saying he didn't disturb that at all.
So the mechanic checked it all over, re-seated all the connectors and cleaned them for anything that was disturbed to get the turbo out. He replaced the plugs and coils. He checked all the physical connections were tight. But still the problem remains. I always run the car on premium 98 fuel.
The car runs beautifully, not rough at all, in fact if it wasn't for the light, I wouldn't even know there was a problem. I'd be tempted to leave it but of course there's no way of knowing if there is a serious check engine problem that arises, because the check engine light would already be on.
I'm a little lost to know where to go from here. If anyone has any suggestions, I'd be mighty grateful. If I make any progress in the meantime, I'll post it back here. Cheers.