Hey guys, quick question for y'all.....

I am gonna try and cut this down to as short a story as I can lol, so bare with me on this one! Okay, so a few weeks ago.....my impreza failed it's MOT on emissions. I was quite surprised, even tho I had changed the exhaust from the turbo back.....cuz I thought it could still pass with the ninja sports cat downpipe and de-cat centre section? But anyway, garage asked if I had the original exhaust and I said yeah, so I brought em over the entire original subaru exhaust (including the backbox, just to make sure!) and they re-fitted all of that.....put it in for it's 2nd MOT.....and it failed on emissions again! Doh! So anyway, I still to this day don't really understand how it actually ended up passing, but it did on it's 3rd test. So when the garage were taking the original subaru exhaust off, and putting my ninja etc back on.....the thread on my oxygen sensor got ruined or stuck in some way, and the guy said he didn't wanna risk putting it into the ninja and messing up the thread on that. He had a spark plug, which he knew was the same thread and so I've got that in my exhaust at the mo while I'm waiting for him to get an oxygen sensor in. Now.....here's the worrying thing.......from what most people have said......running without an oxygen sensor......the car should be WORSE on fuel. Is that correct? Because mine's actually quite a lot better! and that just seems really wrong to me!? Would normally get about 23 / 24ish mpg.......and now I'm getting between 27 - 29.....and I even got 31.3 on a nice long drive to dorset the other weekend!!! I didn't really think anything of this until my mate said that it sounds like it might be running lean cuz it's using less fuel? So yeah I'm a bit worried now. Have I been ****ing it up by driving it without an oxygen sensor? Cuz the guy at the garage said it would be fine, and he's no cowboy, I know him & trust him 110%

Just wanted to check with you guys tho, and see what ya thought

Cheers guys

 

Stick the sensor back in! before the engine goes BANG! You've removed the one thing that measures and adjusts the air/fuel mixture.

Haroon.

 

you obviously don't trust him or you wouldn't be asking the question but as above you need it in to control the mixture

 

I do trust him. I wouldn't take my car to him if I didn't trust him! I just wanted a 2nd opinion, because everytime I get told something by someone.....quite a lot of the time I come on here and ask you guys.....and you give the opposite answer....and this is another example of that! I guess everyone just thinks differently about stuff. It's like the whole dumpvalve thing.......most people seem to say they ruin ur car and stay well clear of em....and other people swear by em and say they've never had any trouble! Nobody ever seems to agree on anything as a whole like. Always some people with a different opinion, so I just wanted to hear them, that's all.

So my question has been answered thanks

Just hope I haven't done any damage

 

On a standard car ECU the lambda sensor is adjusting the AFR to achieve stoich when running off boost. Get the lambda replaced asap but it would be extremely unlikely to do any damage from running without the lambda temporarily. You should not be doing anything to "blow up" the engine.

The improved fuel economy, I cannot explain unless it is just a change in running conditions eg longer journies. What would be interesting would be checking the fuel economy carefully, again, before fitting the lambda sensor and then again afterwards.

Your garage can also look at the AFRs before and after replacing the sensor and comment on their findings.