MOT Failed Emissions
#1
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Thread Starter
MOT Failed Emissions
Hi all,
Forged / mapped 2007 STi.
Just failed on emissions on Thursday.
I did fit a recent brand new Subaru MAF a few months ago as my old one was giving low voltage, it helped but only to a degree.
I've been getting what I see as low bottom end performance for a while.
Would a faulty front 02 sensor cause laggy bottom end performance and bad emission readings?....even though I've never had a CEL?
The 02 sensor has done 100k miles....
Forged / mapped 2007 STi.
Just failed on emissions on Thursday.
I did fit a recent brand new Subaru MAF a few months ago as my old one was giving low voltage, it helped but only to a degree.
I've been getting what I see as low bottom end performance for a while.
Would a faulty front 02 sensor cause laggy bottom end performance and bad emission readings?....even though I've never had a CEL?
The 02 sensor has done 100k miles....
Last edited by Hawkeye D; 02 April 2022 at 09:31 AM.
#4
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Thread Starter
- Exhaust Lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))
- Exhaust carbon monoxide content after 2nd fast idle exceeds manufacturer's specified limits (8.2.1.2 (a))
#5
Scooby Regular
just wondering on the levels if it failed by a mile or a bit , was it hot enough first ? , if they ask for a fast idle , mine passes more easily at 3 k rather than 2.5k , one car i have has to be on hot cats or it’s a no go , the others i keep warm outside the mot place , some one said remove the air filter for the test , im not sure if that works as i’ve never done it , would mot place be able to tell you what exactly it failed on
#7
Scooby Regular
It’s a great shame that you don’t know a proper mot tester 😎
our gas guzzling Subarus are a rare breed on the road now
our gas guzzling Subarus are a rare breed on the road now
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#9
Scooby Regular
The reason i bought jdm , 280 £ tax and ulez exempt , i bought for the long term so have three fairly fresh new shape jdm Fsti and a collection of spare parts including diff gearbox and a forged 2.5 lump 👍 i was lucky i bought before prices went silly ☹️
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#13
Scooby Regular
😂 yes thank you Jdm stig , on a more chilled driving note , take it for a sensible blast before an mot get it fully up to temp and boost , get them to do the emissions straight away on your arrival , keep the car running , keep the revs up a bit before the test , if they have to do a fast idle , on my car 3000 rpm worked better then 2500 , good luck with your test 👍😁
#14
Scooby Regular
unless the original was faulty then a new Lambda will simply replicate the situation...........
have they checked for leaks or done any other kind of basic diagnosis?? has it actually got a functioning cat fitted??
have they checked for leaks or done any other kind of basic diagnosis?? has it actually got a functioning cat fitted??
#15
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iTrader: (3)
😂 yes thank you Jdm stig , on a more chilled driving note , take it for a sensible blast before an mot get it fully up to temp and boost , get them to do the emissions straight away on your arrival , keep the car running , keep the revs up a bit before the test , if they have to do a fast idle , on my car 3000 rpm worked better then 2500 , good luck with your test 👍😁
#16
Scooby Regular
All of this, plus make sure the fuel in it isn't ancient if it isn't driven much.
#17
Scooby Regular
my monaro is the hardest car to pass mot time , if cats are not hot it won’t pass , it’s a well known issue with them , i do the same with my Fsti that have 200 cell sports cats and they are passing no issues , it’s the cheapest option he has at the moment , as before we need to know what it actually failed on and work back from there 😁👍
#18
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Thread Starter
I don't have the car back yet, it's still with the garage waiting to finish off another car so the mapper can plug it in etc. I also don't know the actual emission results as I can't see them online....
I suspect it's running pretty rich as for ages now it's been drinking fuel more than usual....but whatever, never a CEL which is annoying.
I suspect it's running pretty rich as for ages now it's been drinking fuel more than usual....but whatever, never a CEL which is annoying.
#19
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#20
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Certainly nothing on the dash, and I would've thought the garage I use would scan for codes. He has a laptop with pretty good software.....not sure what it's called though.
Would a failing coil pack throw up a CEL on the dash / store a code?
Would a failing coil pack throw up a CEL on the dash / store a code?
#21
Scooby Regular
iTrader: (46)
Yea i have a 100 cell one and its a pain to pass, needs to be roasting hot before it will go though, might try some cat cleaner this year.
my monaro is the hardest car to pass mot time , if cats are not hot it won’t pass , it’s a well known issue with them , i do the same with my Fsti that have 200 cell sports cats and they are passing no issues , it’s the cheapest option he has at the moment , as before we need to know what it actually failed on and work back from there 😁👍
#22
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Thread Starter
Ok car back and running very well.
Bob Rawle was called in in the end, turns out the ECU had "locked" itself on a rich setting / scale....or something like that.
Bob adjusted the AFR scaling to suit.
No idea what would've caused the ECU to do that? Any ideas? Could head gaskets cause the AFR / CO readings on the fail?
Here are the readings :
Fail :
Pass :
Bob Rawle was called in in the end, turns out the ECU had "locked" itself on a rich setting / scale....or something like that.
Bob adjusted the AFR scaling to suit.
No idea what would've caused the ECU to do that? Any ideas? Could head gaskets cause the AFR / CO readings on the fail?
Here are the readings :
Fail :
Pass :
#23
Scooby Regular
good to hear it’s now passed 👍, Bob is going to know way more then me , what did he say ? is car not driven much , flat battery at some point , that’s me guessing
#24
Scooby Regular
Thread Starter
Thanks dude.
Not sure exactly what he said as I wasn't there. It gets driven enough, decent Yuasa very healthy battery.
Perhaps if Bob reads this he'll tell us exactly what he found - Newbury, reg number ending EPA.
Funny you say about flat battery....about a year or so ago, I changed my A/C belt. I wanted to check it was tight enough by running the car at idle and switching the A/C on and off to check for noises.
I did this without the alternator / power steering belt on and it put up an EML.
The EML went out the next day, not sure what the stored code was but I think it said something about the lambda not pre heating or similar? I wonder if it was that incident that the ECU never recovered from...it has been running sh1te for about a year....
Not sure exactly what he said as I wasn't there. It gets driven enough, decent Yuasa very healthy battery.
Perhaps if Bob reads this he'll tell us exactly what he found - Newbury, reg number ending EPA.
Funny you say about flat battery....about a year or so ago, I changed my A/C belt. I wanted to check it was tight enough by running the car at idle and switching the A/C on and off to check for noises.
I did this without the alternator / power steering belt on and it put up an EML.
The EML went out the next day, not sure what the stored code was but I think it said something about the lambda not pre heating or similar? I wonder if it was that incident that the ECU never recovered from...it has been running sh1te for about a year....
Last edited by Hawkeye D; 15 April 2022 at 09:33 PM.
#25
Scooby Regular
from my understanding , if there is a fault ,and the the fault is sorted , the ecu will normally re learn and go back to what it was before the fault , the code (eml ) may come off the dash display but i would expect it to be stored in the ecu till it’s cleared 👍
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