bugblue1

iTrader: (3)

Hi all, replies welcome & help,if i had my car mapped & the o2 was on its last legs but didnt show up when mapped then i replaced o2 with new one would this affect the car,as in poor mpg/perfomance.

piehole1983

iTrader: (7)

It'll probably take the ECU a while to "learn" again after you've fitted the new sensor. You still on a normal Subaru ECU? If so, reset it!

bugblue1

iTrader: (3)

yes it is,had problem while after map i started to lose power now & again with real bad mpg then got o2 cel so changed o2 thinking was problem but havent got back mpg im getting about 15mpg even on a run & i dont thrash it so im bit puzzled,also just changed the 3port for new1 that seem to have made a difference with the power kicking in but havent been on run yet so dont no about mpg,i want to get on RR with Duncan just funds permitting.cheers for reply

toneh

iTrader: (1)

If it's newage ,No it shouldn't affect performance , your car only uses the 02 in closed loop and that's the lower end of the scale , ( idle , moderate acceleration )
There's no need to reset the ecu it'll reset itself after a short while , drive it at various speeds so it can re learn , should only take a few mile
If your mpg and power losses don't return after some spirited driving I would start looking else where for the cause

JDM_Stig

iTrader: (3)

Mapper can tell you the state of the 02 when looking at the laptop,
And yes it will make a small difference, the faulty sensor will at idle say over 1 volt where a good one is about 0.8V, as the ecu uses that voltage to determine the air being flowed it is obvious that any small difference will give the ecu different information.

toneh

iTrader: (1)

Will only make a difference at the very lower end though mate
I if it's losing power when giving it some the 02 is not in use

To the op , are you losing power under normal driving or when giving it a little ?
Btw who mapped it

Jolly Green Monster

iTrader: (4)

front or rear sensor?

If the front o2 sensor is under reading or broken the ecu will richen up using the sensor reading and this will foul/soot the plugs which then would reduce the power a little..

rear o2 sensor would have less of an effect on the mpg as the ecu uses it to check the changes it made on the front sensor readings occur and to check emissions. So if it was faulty it would have less of an effect on mpg.

Simon

toneh

iTrader: (1)

The rear sensor does nothing other than tell you about cat efficiency ( are they working or not ) you don't really need it especially if your running a decat , I didn't use it
The op has not stated where or at what point he feels down on power if it's while he's tootling round then yes I'd agree it's more than Likley 02 issues
If it's under load and high boost and wot scenario It shouldn't make any odds if it's a bad 02 or not ( if it's a good map )

Think we need more info from the op, he's saying its bad after changing to a new 02 ,
If it was mapped on a bad 02 it would have been obvious the 02 was bad from the start

Jolly Green Monster

iTrader: (4)

Rear sensor is not just for cat efficency

toneh

iTrader: (1)

It is , you do not need it

Jolly Green Monster

iTrader: (4)

Sorry but the ecu uses it to also check the fuelling.

toneh

iTrader: (1)

It's tells you 14:1 or not , like a switch , the car can operate solely on the front 02 quite adequately in closed loop

Jolly Green Monster

iTrader: (4)

So you now agree it doesn't just do cat efficiency?

Removing it is different to having a failed sensor, its not used just as a switch

toneh

iTrader: (1)

You know what I mean , it has little or no effect on fueling an doesn't have the same capacity for fuel adjustment that the front 02 does

Jolly Green Monster

iTrader: (4)

It does far less than the front one yes but it is used by the ecu for more than just cat efficiency.. dont agree it has little or no effect but seeing as your refusing to accept that your wrong we may as well agree to disagree as its taking the thread way off topic now

Also the front o2 sensor can effect the long term fuel trims that effect all fuelling, including on boost so could alter the fuelling and now cause det and the ecu is pulling the timing to stop it detting

toneh

iTrader: (1)

Why would the front O2 have an affect in o/l
Genuine question ,



I didn't run a rear 02 btw and it had no affect at all on my fueling at all
Why would that be
Another genuine question

I'm not totally disagreeing Simon , you know I just say what I see
I've had 02 locations , configurations and scalings coming out of my ears
Just to see the effects

Jolly Green Monster

iTrader: (4)

The ecu will trim fueling using the front o2 sensor, if its a long way out it will alter the long term trims which effects the whole map.. often see incorrectly mapped cars where the cruise afr has been left to the ecu to correct and over time it then pulls fuel out the whole map or adds it.. just need to see the whole picture. Perfect example is when fitting larger injectors like sti 550cc in a WRX, it starts and runs rough and then the ecu takes a few seconds to alter the fueling and it will drive 90% okay.. you switch off and restart the engine and it doesn't return to the rough running as it retains the long term trims it learnt when it last ran.

Yes no rear lambda fitted wont necessarily show any affect but doesn't mean to say it is not having an affect and changing the function of the lambda sensor setup on the car, but more importantly to this particular thread he hasn't removed it.. one of the sensors is believed to be nearly dead when mapped and then faulty and then replaced.. not removed.. therefore a sensor reading wrong will have a different effect than no sensor at all. It could read rich and the ecu adjust the fueling appropriately and leaned the fueling out and with it mapped like that so changing the sensor then means it is now running lean, or it could have been reading lean and mapped to get the fueling appropriately mixtured and now with the faulty sensor replaced it is reading rich.. or it could have been the heater part of the sensor that was faulty so when the sensor is cold it reads incorrectly, adjusting the fueling unnecessarily and then readjusting it when the sensor is heated sufficiently by exhaust fumes, although the heater is used when engine is cold, it will sometimes drop below the working temp of around 300deg C, in normal operation and require the heater to keep it above that temperature.

Really we need to know from OP which sensor was faulty and replaced..

Simon

toneh

iTrader: (1)

Got it , so you're saying if the hardware or map is poor and miles out in c/l it will struggle to correct itself even after the switch , due to the amount of correction needed in the given time

So the reason I personally didn't have issues was because my hardware was operating correctly ( when fitted ) and my map wasn't a million miles out

Jolly Green Monster

iTrader: (4)

No your muddling the two situations (yours and his) and the senario.

It will adjust and if it exceeds certain limits it will adjust the long term trims that effect the whole map, closed and open loop. If it was mapped with a dying sensor it could now be adjusting the whole map as it was mapped to a different correction trigger.

toneh

iTrader: (1)

Lol I give up , it will adjust , it won't adjust ,

Right then you map a car with an intermittent fault with the 02
During the mapping the 02 is reading x at a certain point so the progression is following on from x
Then you swap sensors and at the same x point the sensor is saying y so the whole map ( theoretically ) is now all over the shop

Just had a thought , do you mean a similar scenario to let's say a maf that's incorrectly scaled before you start , thus tuning to an illusion type effect

bugblue1

iTrader: (3)

Thanks chaps for replies.ok this is what happened got car already had turbo back exhaust on some idiot had cut cel light so sorted that light was on because of exhaust,got it mapped & used 3port solenoid,was going great noticed big difference only thing was neutral switch needed replacing so replaced that,then every now & then it would seem that car was back standard loss of power throughout,but this didnt happen all the time,then replaced fuel pump for uprated 255 had map tweek which made another big difference duncan even asked had i done anythink else to car as he got another 3degrees of timing,car eventualy got to the point where it felt bogged down all the time,then i get front o2 cel so i think great must be problem changed o2 for new denso didnt make any difference apart from put out cel,so last week i buy another 3port solenoid as tyhought this was only part i had put on that was second hand,now this seems to have made a difference seems like pulling well dont no about mpg yet but will find out in couple of days,but after all this could it be the 3port or has it been mapped with a dodgy sensor thats making it run bad,i mean would a 3port cause this? thanks for all learning loads chaps with ya discussions..

toneh

iTrader: (1)

Lol , I had a feeling there was a little more to your problem , all of the niggles you have had can cause issues ( some more than others )
Seems like Duncan has been up against it chasing a few problems

I feel it does help to go a little astray from the original question
Would be a pretty boring forum if every answer was a straight yes or no

dynamix

iTrader: (3)

I am up in norfolk next week mate - gimme a shout and I am sure we can hook up and I can check it over before you spend any more money chasing phantom faults or internet diagnosis potential issues

As said, the O2 sensor can have an effect on the long term fuel trims and cause it to remove or add fuel in the open loop (ie on boost) areas. this can drown performance or cause it to run dangerous if the sensor was massively out at the time of mapping. I don't recall it being hugely out tbh though but happy to check over for you - really will not take long to restore it to former glory

bugblue1

iTrader: (3)

thanks all,cheers duncan i did go on your website last night to see if you were going to be this way,its just been funds at mo little low as son just been off to uni & he's bleeding me dry.
i would like to point out that i have been very happy with Duncan & his work its my own fault realy i should of had it on RR with him.
now since ive swapped 3port over car does seem to be alot better il find out tommorrow about mpg as will be doing couple hundred miles,il take up your offer duncan as would like to make sure it is right il give you a call at weekend if ok.many thanks every one

dynamix

iTrader: (3)

I only have the dyno mapping days on the website - not the full extent of where I travel for road mapping so always best to gimme a shout to see when we can hook up.

bugblue1

iTrader: (3)

the car was fine after duncan done his job cant complain with his workmanship tiptop,due to funds havent been able to get it on RR with duncan,its been a rearly strange fault.

bugblue1

iTrader: (3)

Evening chaps,ok did 200miles today averaged 24mpg which cosidering i was taken it real easy didnt think it did that well,as it was mostly motorway/dual carriageway as weather was v.poor didnt go over 70,it was mostly 60 definetly use to get more ive always use tesco99 from same garage.so any thoughts on that any one.will be interesting to get it back in duncans hands to see if a possible dodgy sensor would cause such issue's.
on a plus side car does feel more alive i still get a bit of over boost but thats v.rearly & a over rev when changing gear.any thoughts would be interested to hear as like to hear the possibilities.Many thanks

bighead

iTrader: (1)

24mpg ...and yr complaining ??......that is good Bud trust me I wish all my cars can average 24 mpg !!!( E90 M3 16.7 mpg, Impreza P1 2.35 forged 20mpg !! )

bugblue1

iTrader: (3)

Not complaing fella,i wouldnt of brought a scooby if i was woorried about petrol, its just it was doing about 30mpg on runs then went down to 15mpg,so im guessing prob somewhere as just dont drop mpg like that,what ive been told over the years is that a drop in mpg is sign of somethink not right or start of somethink.im going to change plugs before i hook up with duncan to see what their like as last time i had a look at them they werent sorted up as i exspected look more lean than anything.i like to get peoples opions on things like this as you can learn so much good way to find out how things work & what happens when they go astray.cheers everyone...

bighead

iTrader: (1)

no probs m8...but I doubts many on here average 30mpg in day to day running....low 20s mpg more like