Hi everyone just a quick question to ask, i have recently replaced all of my o2 sensors on my type r after having a decat pipe fitted and am now getting a system too lean bank 2 I also had a bank 1 too lean but this seems to have sorted itself out , I have read up that I should possibly do a hard reset on the ecu so that my fuel trims reset and see if that helps?

My only worry is that shouldn't new o2 sensors automatically adjust its fuel trims or have I just uncovered a possible vacuum problem or air leak of some kind?

Also wondering whether it's the decat that has triggered it as I haven't had this lean problem beforehand, also been told that if one of the welds aren't fully sealed near the o2 bungs this could also cause the sensors to read lean,

ive attached a quick freeze frame of my data but need to invest in a live reading diagnostics tool to better see what's going on especially if I reset the trims,

any my info at all on this would be much appreciated, thanks in advance

 

They should relearn. (You can do a hard reset potentially to speed it up but beware that this can get you into Catch-22 where there's a fault but the car can't set its monitors so can't diagnose the fault.)

You'd expect the STFTs to change from what they used to be and then the changes should migrate into the LTFTs with time (the clue is in the name).

If all's OK the STFTs and LTFTs should end up near zero - for a normal (petrol) car.

If you've a fault (or some non-standard item) they won't get to near zero.

As ever, if there's an air leak you can see it in the trims, but if the relearning hasn't finished you either wait till it has or do mental gymnastics on both STFTs & LTFTs.

Any leak (at a weld or wherever) is a problem.

A decat ... what now? The car needs cats!

 

Basically I took the cats out because of a stuttering problem I had on acceleration and it also used to completely lose power at wot occasionally just for a split second and then be fine, I changed many many things which I thought could be the culprit but I was also having the carbon smell from the exhaust after a hard run.h

I decided to take the leap of faith and have the cats chopped just temporarily purely to see if it would make any difference, in typical fashion it did nothing for the performance problems or the power jolt, but in the process it gave me these lean codes and restricted performance so no power over 3k rpm so it didn't end up helping at all, I intend to put some sports cats on as a replacement soon.


I'm just not getting anywhere with my issues and I've spent nothing but time and money trying to get it right, but as you say I will try resetting the fuel trim adaptions and then watch over it to see if it reverts back to where I am now and go from there

I've started to consider whether or not one of my fuel pumps are dying out and thus giving me this spluttering and engine cut out problem but on idle the fuel pressure came back ok although I will need to check fuel pressure whilst driving to really see if there's a problem

 

I think you got it with your last paragraph !

You can watch your fuel pressure with a obd2 scan tool . As you know
The second fuel pump should kick in about at the rpm's your seeing the issue .
Should spike to around 70psi

 

Bank 2 looks to be lean, fuel trim is compensating big time. I would think with the cats removed that is what you would see. But 1 is not too bad actually just a little rich recently when it should probably be lean from the cats. I'm thinking you MAY be dealing with an injector or intermittently bad coil or plug on bank 1. There are no misfire codes at all? Either way you are never going to get it right without cats. If I am wrong feel free to abuse me! When you get it running right The stft will be off - about as much as the ltft is+ until the LTFT comes back in line. When your total STFT+LTFT is 5 or less you are doing pretty good and have probably licked your problems.

 

Could easily be the 2nd fuel pump but either way you either need the cat(s) back in or find somewhere that can genuinely program them out (good luck!!) and even then the back pressure will be wrong so power down.

 

yeah I'm definitely getting some sports cats made up as decat is too much of an issue at the moment and it's just causing more problems than I need.

I've managed to source some fuel pumps but don't want to put them in yet because of these issues caused by the de cat, going to sort them first and go from there.

I live near the jag specialist in Doncaster so I'm thinking of going to see him as I've heard he's good and hasent been beat yet, saves me throwing more and more cash at the problems that I can't pinpoint, cheers for the input though guys