Mot Failure, emissions issue?

[Bristol spark]

My S2000 failed her mot today with a nice list of failures

Mostly Emissions , plus the chassis next to seatbelt mount has rusted through!


With the emissions I'm told both the Co and Lambda are way out.

Ive just fitted a brand new Cat ( had a decat), however there is a slight leak between the headers and cat, as i forgot to fit the gasket. Would this cause an emissions issue?

Also to get the lambda out of the decat pipe i had to heat the fk out of it, which in turn melted the threads slightly.
So it never threaded all the way in, its around 1/4" proud of where it should be.
Would this cause an issue? I would have though as long as its in a bit, it should work?

Or is it likely something else?

I replaced the headgasket myself last year, could i have buggered up the timing? Would this effect the emissions.
I would have expected the engine to have gone bang by now if id done this though!


Anyone any ideas?


My list of failures

Anti-lock braking system warning lamp indicates an ABS fault (3.4.1c)
Exhaust emissions carbon monoxide content after 2nd fast idle excessive (7.3.D.3)
Exhaust emissions Lambda reading after 2nd fast idle outside specified limits (7.3.D.3)
nearside front inner Seat belt anchorage prescribed area is excessively corroded sill (5.2.6)
offside front inner Seat belt anchorage prescribed area is excessively corroded sill (5.2.6)
nearside front Brake hose has insufficient room to move, resulting in fouling on any part insurecure (3.6.B.4a)
offside front Brake hose has insufficient room to move, resulting in fouling on any part insurecure (3.6.B.4a)
offside Front position lamp(s) not working (1.1.A.3b)

Edited by Bristol spark on Wednesday 7th December 18:04

[anonymous-user]

Yes leaky headers could cause a problem with the emissions, anywhere you're getting un-metered air into the intake or exhaust messes up what's supposed to be a closed loop system.

If you're sucking air into the exhaust before or at the pre-cat lambda then it will be getting an incorrect reading on the exhaust gasses because it's picking up too much oxygen so it thinks it's running lean, which causes the ECU to add more fuel, which then gives stty HC and CO emissions because the car is actually running too rich.

[Fastpedeller]

We had an out of spec lambda figure at MOT due to a post-cat leak which led to a too-high AFR reading at the tailpipe (air 'weakening' the mixture). I'm surprised 'running lean' would be an issue, as that uses less fuel than running rich. Of course the engine wasn't running lean anyway, it was just the reading (like would happen if the sensor was outside the tailpipe). MOT man put some exhaust putty on the joint, and with a rag around sensor in tailpipe it got in the range of ok.

[Loyly]

My 106 Rallye got a hole in the exhaust manifold, just before the link to the cat. It didn't really affect the running in a sense that you could feel, other than causing a 'hiccup' in the fuelling every now and then. It also had the emissions readings shot to st as the engine was running a bit rich.

[Bristol spark]

Thanks Guys, Will pop by in the morning to give them the heads up before they start diagnosing things tomorrow.



Cant quite get my head around how air can get in, while air is being forced out! But I'm sure your right!


Ive already had to admit to bodging the ABS and brake flexi bracket, they will think I'm a right numpty

[Petrolhead_Rich]

Bristol spark said:

Thanks Guys, Will pop by in the morning to give them the heads up before they start diagnosing things tomorrow.



Cant quite get my head around how air can get in, while air is being forced out! But I'm sure your right!


Ive already had to admit to bodging the ABS and brake flexi bracket, they will think I'm a right numpty

more that gasses escape thus lowering the readings to be fair.

Heating the Lamba sensor to the point where you're melting it could well have knackered that, for the sake of it, I'd replace with a new or scrappers sensor!

Bodging the ABS/Brake Hose bracket doesn't sound good either to be honest!!

[Dr Doofenshmirtz]

Well it should be pretty obvious to anyone who actually knows what they're talking about that you've knackered the lambda sensor - get a new one & fit a header gasket - job done.

[Dr Doofenshmirtz]

Bristol spark said:

Cant quite get my head around how air can get in, while air is being forced out! But I'm sure your right!

It won't be sucking air IN - they're talking nonsense.

[Loyly]

Dr Doofenshmirtz said:

It won't be sucking air IN - they're talking nonsense.

A missing gasket wouldn't suck air in, but the hole in my exhaust manifold definitely did. I suppose between the exhaust pulses the lower pressure inside the pipe pulled air in through the hole. Not a massive amount, but enough to throw off the Lambda sensor reading. Don't forget, exhaust systems exhibit a scavenging effect when they're tuned correctly, and they will no doubt scavenge at any port they can if it's upstream of the return pulse.

[OldGermanHeaps]

Bristol spark said:

Thanks Guys, Will pop by in the morning to give them the heads up before they start diagnosing things tomorrow.



Cant quite get my head around how air can get in, while air is being forced out! But I'm sure your right!


Ive already had to admit to bodging the ABS and brake flexi bracket, they will think I'm a right numpty

I think you should give up on diy on your car and do every other road user near you a favour and pay someone competent to keep the thing roadworthy.

[Little Pete]

An exhaust leak wil generally give a high lambda reading i.e. above 1.030 and a high CO reading will give a low lambda reading i.e. below 0.970. I suspect you could have two faults here, a leaky exhaust and a sha@@ed sensor.

[Welshbeef]

That's a pretty poor list of fails all caused by OPs shocking DIY car mechanics.


OP could you list the advisories too please

[anonymous-user]

Welshbeef said:

That's a pretty poor list of fails all caused by OPs shocking DIY car mechanics.


OP could you list the advisories too please

Basically.

[Bristol spark]

Had a call earlier from the Garage the Culprit was actually the Pre Cat Lambda that was faulty, not the one i attacked with the blow torch or the leak.

£600 later and she has passed with no advisories.


Oh and to those who don't believe in my mechanical abilities, don't ever buy a red Kitcar with the Reg: WX62 HDC as i built it

Edited by Bristol spark on Thursday 15th December 19:36