Suddenly terrible fuel economy

[mookstix]

Hey guys, brought an '03 XR6T ute recently and it's suddenly become a crazy gas guzzler. I can't give too much info on the car, it's had some work but I have no real idea about it's history so I want to get a proper tune. It's lowered etc. but the only performance mods I can see are a full 3 inch exhaust and a new turbo. It's an AR.50 but the compressor wheel looks way, way bigger than stock, solenoid looks stock but not sure about the wastegate. I've had it for about 3 months and have been using it daily and it's been great, but not perfect, doesn't feel like it's making stock power. Waiting on a hard turbo pipe kit as an Xmas present to myself, then the exhaust, new resonator I'm thinking, then a proper tune as it feels mechanically fine. As I said though it's had a huge spike in L/100km that I can't seem to quantify. It feels the same, sounds the same, but it's gone from a steady 12L/100km, which is not great hence wanting a tune, to an amazing 20+L/100km. This is backed up by on road consumption. Like I said, no change, no smell of gas, no leaks. Still makes it to redline easy, still pulls ok, all vacuum pipes present and accounted for etc. I can't seem to figure it out. Also it's factory interior is gaugeless so I'm not sure of any boost numbers yet. Yes I need some gauges and yes they're on order, just need to recover from the initial cost of the car before I can drop anymore $ on it.

 

My question is are there any obvious reasons for this that I should look at rectifying BEFORE the tune, or is it most likely tune related and I should just deal with it till I can get that done? I'd rather get everything I can sorted mechanically before the tune, not keen on having to go back for a retune for something like an 02 sensor etc.

[k31th]

 

you can get the car run up on a dyno (significantly cheaper than a tune) to check on the AFR numbers to see what's happening there, but it does sound like an O2 sensor issue by what you've said, but that's only really guessing without numbers to back it up.

[JETURBO]

Yeh mate, throw a new upstream sensor at it first 

[mookstix]

Yeah sounds like the best idea, the garage I'm getting the tune done at says they can do a dyno run mid Jan to check before a full tune but to make sure I got a boost gauge first. Also gonna pick up an 02 and put it in today, I found yesterday that the bracket was actually broken and it was hanging down by the steering column, cheap and easy enough so why not replace it and see. Cheers fullas.