Colin from Hull · Jul 13, 2012

Hi, My P38 failed its MOT on some simple items, but the one im not sure how to solve is failure on emissions. I havent any experience of CATs and Lambdas. This is how it was described on sheet

(cos high) Exhaust emissions carbon monoxide content after 2nd fast idle excessive.

Exhaust emissions Lambda reading after 2nd fast idle outside specified limits.

The chap said my cats were getting far too hot, and he just couldnt do anything with it, he also advise me to replace my manifold covers.

My first thought was new cats and lambdas! if so any advice on good deals anywhere! Or is there anything i should check before-hand which affects the emissions. cheers Colin

Druim · Jul 13, 2012

Diagnostic is your friend, (on mine it was 1 Lambda sensor causing it to run rich)

Saint.V8 · Jul 13, 2012

A duff lambda sensor would create incorrect fuelling which could lead to a hot cat!!

shaun69 · Jul 13, 2012

Saint.V8 said:
A duff lambda sensor would create incorrect fuelling which could lead to a hot cat!!

I wood 2nd that

eightinavee · Jul 13, 2012

Or you could let someone check it out properly.Oxygen sensors and Cats often get the blame for emissions failure - they get changed and the results are the same.The oxy sensors will only switch if the engine is running well enough to allow them to,the cats will only work if the oxy sensors are being used by the engine ecu and its running on all its cylinders.A rust hole in the exhaust or a cracked vacuum pipe can be enough to put things out of limits and make the engine run open loop.Running properly any RR petrol will pass its emissions test with ease,so for it to fail there has to be something clearly wrong.
Find a local indy by recommendation and get them to sort it.

2.0_hippo · Jul 13, 2012

Often a simple emission test failure can be solved by a quick rag around the block !

eightinavee · Jul 13, 2012

2.0_hippo said:
Often a simple emission test failure can be solved by a quick rag around the block !

Notice that the OP said it failed after the second fast idle test - there WILL be something wrong with this car,if it was running right it would be running closed loop after 15 secs from cold,and soon be hot enough for the cats to light - no Mot tester is daft enough to run a test with a cold engine,the emissions testing kit will ask for oil temp or at the very least a check for hot coolant hoses.
Remember VOSA is looking at MOT stations online,anyone having multiple failures for the same things will flag up and be looked at.

Bix · Jul 13, 2012

eightinavee said:
Notice that the OP said it failed after the second fast idle test - there WILL be something wrong with this car,if it was running right it would be running closed loop after 15 secs from cold,and soon be hot enough for the cats to light - no Mot tester is daft enough to run a test with a cold engine,the emissions testing kit will ask for oil temp or at the very least a check for hot coolant hoses.
Remember VOSA is looking at MOT stations online,anyone having multiple failures for the same things will flag up and be looked at.

Indeed, you don't run the test with a cold engine, but more often than not when failing on emissions if you go for a hard drive (Vauxhall used to recommend 70mph in 4th for 30 minutes) will clear out the muck and get you through the emissions test. Some times it'll stay clear for a good few years, others it'll just come back next year.
And what goes online is only what the tech enters, you can still get techs who'll fudge the results if you slip them a few notes.

eightinavee · Jul 13, 2012

Bix said:
Indeed, you don't run the test with a cold engine, but more often than not when failing on emissions if you go for a hard drive (Vauxhall used to recommend 70mph in 4th for 30 minutes) will clear out the muck and get you through the emissions test. Some times it'll stay clear for a good few years, others it'll just come back next year.
And what goes online is only what the tech enters, you can still get techs who'll fudge the results if you slip them a few notes.

That maybe for multivalve engines in a higher state of tune with marginal cat capacity - a Gems or Thor V8 will sail through its emission test if its in any sort of decent shape,even after 100k mile with a worn cam etc.Its an old pushrod motor with small valve overlap and bloody great cats - very little comes out the tailpipe if its half decent.
The gas testers all print out reports which the station has to keep for VOSA,its not 100% foolproof,but the owner of the car is only wasting fuel if it wont pass properly.

Bix · Jul 13, 2012

How about that a cat that actually works. Good to know Range Rover drivers are helping everyone live longer. Unlike those selfish Prius drivers who are bathing us all in smug and acid rain.

So does the emissions tester now automatically upload the results? I was of the understanding all that changed was the way the cert is printed out as it then forwarded a copy to DVLA, nothing else was going to change in terms of testing equipment.

Colin from Hull · Jul 14, 2012

Hi, Thanks for replies. Just before MOT i had RAC man to my car because of flat battery, he told me i wasnt get full charge to battery from alternator and to check connectin on starter motor.
At the time i told him that my car had recently started to HUNT a little, and tickover would fall sharply. He mentoned that he fell it wasnt firing on all plugs. So i will start here and check the obvious things, i have some spare sensors so i will take these to my local garage when getting it tested. thanks again for replies. Colin

Colin from Hull · Jul 14, 2012

Hi, Just an update on what i found today, decided to check plugs, facing front of car, lefthand side plugs were white and clean, righthand side were more brown one cracked (so need to replace).
About a year ago i replaced engine but didnt replace heat shields, because of this, the righthand manifold had melted the two black plastic boxes underneath so couldnt see from adove (air-take). I re-assembled all together, had a drive, but couldnt say i noticed much difference.

treeman · Jul 16, 2012

Colin from Hull said:
Hi, My P38 failed its MOT on some simple items, but the one im not sure how to solve is failure on emissions. I havent any experience of CATs and Lambdas. This is how it was described on sheet

(cos high) Exhaust emissions carbon monoxide content after 2nd fast idle excessive.

Exhaust emissions Lambda reading after 2nd fast idle outside specified limits.

The chap said my cats were getting far too hot, and he just couldnt do anything with it, he also advise me to replace my manifold covers.

My first thought was new cats and lambdas! if so any advice on good deals anywhere! Or is there anything i should check before-hand which affects the emissions. cheers Colin

The lambda reading is just that, a reading by the exhaust gas anerlizer it doesn't indicate that there is a problem with your lambda sensors you do have a slight problem though as your cos were too high but lambda readings can be thrown off the scale by something as simple as holes in your exhaust sucking air in as was in my case 2 mot's back we found holes in the top of the centre box sucking in air and throwing out the lambda reading as both my CO and HC readings were fine once box was replaced lambda readings were what they should have been. So just a thought check your exhaust for holes, they don't have to be that big either.
Hope that helps

Colin from Hull

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Colin from Hull

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