MOT failure - Catalytic converter lambda sensor readings
Discussion
Any of you guys ever had an MOT failure due to lambda sensor readings ?
I've got the DAE power upgrade which has the different headers, cats and remap.
These have been fitted for years and always passed the emissions previously.
For info, allowance is 0.97-1.03 and mine were reading 1.164 (Fast idle) and 1.172 (Second fast idle). NOTE: MOT done at AM Dealer, so they knew the car needed to be 'hot'.
Not sure the best way to understand what can be done to fix.
Any advice appreciated before I start removing the cats.
I've got the DAE power upgrade which has the different headers, cats and remap.
These have been fitted for years and always passed the emissions previously.
For info, allowance is 0.97-1.03 and mine were reading 1.164 (Fast idle) and 1.172 (Second fast idle). NOTE: MOT done at AM Dealer, so they knew the car needed to be 'hot'.
Not sure the best way to understand what can be done to fix.
Any advice appreciated before I start removing the cats.
Perhaps they could tell you whether you have a dodgy sensor or a dodgy cat. Quite a difference in price I would imagine.
It brings back memories I can now laugh about, namely my first and last dealing with Scrotum Motor Company, who tried analysing lambda sensor data to fix my gearbox... but take pity on them, it was the only data they managed to find in a week. Moral is - just because they say they're good, they may not be.
It brings back memories I can now laugh about, namely my first and last dealing with Scrotum Motor Company, who tried analysing lambda sensor data to fix my gearbox... but take pity on them, it was the only data they managed to find in a week. Moral is - just because they say they're good, they may not be.
Was the car actually hot when they tested t? Had the car been in frequent use?
I’ve had a similar issue recently (not the Aston, but very similar mods - no primary cats, 100 cell sports cats, etc) but it’s not been driven much. They said to take it for a good run and bring it back and they would retest it. Did exactly that, full filled up with fresh fuel. I’d see if you can get it booked in somewhere else, so it can be tested as soon as you bring it in after a very long run.
I’ve had a similar issue recently (not the Aston, but very similar mods - no primary cats, 100 cell sports cats, etc) but it’s not been driven much. They said to take it for a good run and bring it back and they would retest it. Did exactly that, full filled up with fresh fuel. I’d see if you can get it booked in somewhere else, so it can be tested as soon as you bring it in after a very long run.
It was definitely hot and just come back from a 1000 mile round trip. I actually took the cats off earlier and they look pristine, so I'm hoping it might be an exhaust leak (as lambda readings are high, means too much oxygen in the system) This does coincide with my exhaust vacuum valves not working properly. Fingers crossed if I sort the vacuum hoses out, then no leak and readings within limits.
V8VS said:
I've had a similar issue recently (not the Aston, but very similar mods - no primary cats, 100 cell sports cats, etc) but it's not been driven much.
100 cell seems low. Does that installation usually pass the test?
I might have changed from 1300 to 400 on a V8V (pre-manifold cats model) and at every subsequent MoT, the emissions readings have not changed at all.
It's going to be an air leak somewhere, that reading has nothing to do with the cats other than to affect the results of the other readings. What were the other figures?
Lamda readings were added to stop people introducing air leaks to drop the CO to a level the car would pass, in the past slipping the pipe off the pcv valve would do the trick...
Lamda readings were added to stop people introducing air leaks to drop the CO to a level the car would pass, in the past slipping the pipe off the pcv valve would do the trick...
I got fed up with having to get the car super hot to pass an MOT with the 200 cell cats, it was always a knife and fork exercise with the MOT, despite the tester being friendly and knowing what to do to get it through on second attempt.
Then last year no matter how hot we got it, it just would not pass. So I returned it all to standard manifold and cats and it passed MOT that year and this year from cold no issue. I even much prefer the noise, valves open or closed, of the standard V8VS system.
Is it a tad slower, less responsive? Maybe. Honestly I can't really tell one way or the other. By far the best upgrades for these cars is good, well set up coilovers and the twin plate clutch.
Then last year no matter how hot we got it, it just would not pass. So I returned it all to standard manifold and cats and it passed MOT that year and this year from cold no issue. I even much prefer the noise, valves open or closed, of the standard V8VS system.
Is it a tad slower, less responsive? Maybe. Honestly I can't really tell one way or the other. By far the best upgrades for these cars is good, well set up coilovers and the twin plate clutch.
I got fed up with having to get the car super hot to pass an MOT with the 200 cell cats, it was always a knife and fork exercise with the MOT, despite the tester being friendly and knowing what to do to get it through on second attempt.
Then last year no matter how hot we got it, it just would not pass. So I returned it all to standard manifold and cats and it passed MOT that year and this year from cold no issue. I even much prefer the noise, valves open or closed, of the standard V8VS system.
Is it a tad slower, less responsive? Maybe. Honestly I can't really tell one way or the other. By far the best upgrades for these cars is good, well set up coilovers and the twin plate clutch.
Then last year no matter how hot we got it, it just would not pass. So I returned it all to standard manifold and cats and it passed MOT that year and this year from cold no issue. I even much prefer the noise, valves open or closed, of the standard V8VS system.
Is it a tad slower, less responsive? Maybe. Honestly I can't really tell one way or the other. By far the best upgrades for these cars is good, well set up coilovers and the twin plate clutch.
Calinours said:
I got fed up with having to get the car super hot to pass an MOT with the 200 cell cats, it was always a knife and fork exercise with the MOT, despite the tester being friendly and knowing what to do to get it through on second attempt.
Then last year no matter how hot we got it, it just would not pass. So I returned it all to standard manifold and cats and it passed MOT that year and this year from cold no issue. I even much prefer the noise, valves open or closed, of the standard V8VS system.
Is it a tad slower, less responsive? Maybe. Honestly I can't really tell one way or the other. By far the best upgrades for these cars is good, well set up coilovers and the twin plate clutch.
Lets see if the car passes tomorrow, I found a little leak at one of the exhaust pipe junctions which might not have helped. Since getting the power upgrade, its always passed MOT, but i know its been close. Last resort is to swap back to the old cats, I love the noise........Then last year no matter how hot we got it, it just would not pass. So I returned it all to standard manifold and cats and it passed MOT that year and this year from cold no issue. I even much prefer the noise, valves open or closed, of the standard V8VS system.
Is it a tad slower, less responsive? Maybe. Honestly I can't really tell one way or the other. By far the best upgrades for these cars is good, well set up coilovers and the twin plate clutch.
Well it passed the MOT, so I can only assume it was the minor leak in the exhaust that was causing the failure. I did go through and recheck all the joints from the Cats backwards. For info, this was my 'DIY' smoke detector. Relatively cheap solution........Managed to find some cardboard tube from a paper towel roll that slid just over the exhaust pipe, almost a perfect fit
Gassing Station | Aston Martin | Top of Page | What's New | My Stuff