Hey everyone. I'm the proud new owner of a 2004 v70 2.5t with 138k. (had a 240 about a decade ago, and now I'm back)
Here's my situation. I've had the car for about 2 weeks now and had it checked out by my mechanic (whom I trust a great deal) before purchase. He gave it a clean bill of health.
5 days ago, the CEL came on.
I took it to Autozone and they read the code. Not sure of the number but it suggested that the car was "running rich"
I am 1/3 of a tank into a fresh fill up of Premium Fuel (93)
It was my first fill up since purchase
I have no idea what sort of fuel the previous owner ran.
They said the fuel change is likely the culprit and that 93 octane is unnecessary with such a low compression engine (and that even the turbo is low compression), They suggested that regular fuel would be fine.

I've read a bit on the board about the fuel octane debate, but was looking for input for my particular situation. The car is not to be driven aggressively. My wife uses it for city driving primarily and only about 10 miles a day rarely if ever getting up on the freeway.

I'd love any thoughts you guys have.
Thanks!

 

Changing fuel octane will not trigger a CEL; that's poppy-****.

As far as octane recommendations, follow the owners manual guidelines.

Report back with the CEL number and we can go from there.

 

+1 With GDog, the CEL poped for a reason. Please get the code and post it back so we can get to the bottom of it.

The owners manual recommends 91+ octane. Mainly because it's a HIGH compression motor. Anything above 9.0:1 is considered high. I have switched back and forth several times and never got a CEL.
2004 VOLVO V70

The fact that it is a turbo car would make you want to run higher octane fuels, not because it's high or low pressure turbo, but because it can rev the motor up much faster than a NA motor.
2004 VOLVO V70

If we were in a gussing game, my guess would be that you have a vacuume leak or something like that.

 

Here's some more information. On startup, the car settles to idle smooth at 600rpm then after about 20 seconds, the engine lulls then surges to 1500rpm only once. It only happens once, then it runs fine.

The codes are:
P0288
P0420

I took a look at the hoses and they all seemed intact. But I must admit that I wasn't quite sure what I was looking at/for.