Does removing the N249 and N112 and not fitting resistors affect emissions come MOT time?

I`m asking because I removed the SAI and the N249 + N112.   I know I removed the SAI first and left the other parts on the car for a while.  I`ve just had an MOT and my car failed on its MOT.  I`m trying to work out whether the N249 and N112 would affect the lambda readings.  Last time I had the MOT it passed emissions test but I can`t remember whether I had the N249 and N112 in place for this test.  I know for certain the SAI was completely removed..

 

The only error I get on the ECU is the secondary air injection error and I`ve always had that error.

 

 

The N249 controls the DV so that shouldnt affect emissions and the SAI only serves to heat the cat quicker on cold start up so that shouldnt either

Yeh that's true.  Do we know what purpose the N112 serves??

If you have access to VCDS check the coolant temp sensor reading to the ECU as CTS failure is very common & causes the ECU to overfuel resulting in poor emissions.

Edited 7 June, 201412 yr by pauldazzle

Yeh I`ve recently had a brand new genuine CTS fitted.

Yeh I`ve recently had a brand new genuine CTS fitted.

Unlikely to be that then. Still worth trying to hook it up on VCDS to see if all the relevent sensors are working correctly. There's a few that can go wrong without causing fault codes.

These are the results of MOT:

 

FAST IDLE TEST

Passed on HC

CO % Max 0.300, Actual 1.749  Fail

Lambda Min 0.970, Max 1.030,  Actual 1.060

 

Second Fast idle test

CO Actual 1.898

Lambda actual 1.016

 

Idle test

CO Actual 0.223

 

 

These results don`t really mean much to me.  I`ve recently given it a real good blast with some cataclean as advised by a good mate of mine.  I`ve got it booked in Monday for another emissions test and the MOT guy just recommends I give it a real good blast down the motorway and get it nice and hot before the test.

Edited 7 June, 201412 yr by sammyhale30

I was just looking at my last MOT emissions test and the actual value of CO on the fast idle test was only 0.010!  Big difference..

As the lambda reading is almost spot on, I would take a guess at the CAT not working properly. 

 

Have you checked for fault codes yet?

With those readings I'd say the cat is shot. Especially as lambda is good so no air leaks on the exhaust side.

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yes only fault I get is the secondary air injection fault because I have removed SAI.

So are we saying the CAT might be dirty/blocked up or fooked altogether? 

Edited 7 June, 201412 yr by sammyhale30

Could be blocked or forked all together. Get it on the motorway and kick the cars arse low gears 3/4 and batter it

Time for a decat [emoji16]

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Yes I would like a decat but that won`t get me through the MOT..

I had cambelt change in the past month too. Would a cambelt change affect emissions???

The belt could only affect the emissions if it was a number of teeth out . It would have to be out enough to cause bad running/misfire

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It failed again today.  The MOT guy said when it gets to the 3000rpm mark the CO goes well over the max.  It should be 0.9 max but it jumps upto 1.7, 1.8 at 3000rpm.

I`ve fitted some resistors today to the SAI and N249 to see if that helps at all..

Edited 9 June, 201412 yr by sammyhale30

Italian tune up required!

 

Mine failed on emissions on the first try as the car had just been pottering around town on short trips for a week. Took it out for a boost/load heavy drive to get exhaust temps right up and it sailed through with flying colours 30mins after it failed....

 

The MOT tester couldn't believe the difference in results.

 

I think it's just a side effect of an old cat (mine's 12 years old).

Yeh I have done this already.  I put cataclean through it and gave it one hell of a blast down the motorway before the test.  But results were exactly the same as before.  I`ve fitted some resistors on the SAI , N249 and N112 connectors and reset the error today.  The error was SAI valve open.  So hopefully this might help..

My mechanic mate thinks that if the ECU thought the SAI valve was open all the time it might have been over fuelling which caused the high emissions.  Only the retest will verify this though. 

Ok results the dread engine management light appears to have gone away now! lol

However I borrowed a vgate scanner from a mate.  I ran engine tests and everything seems ok.  BUT

 

When I run readiness test I get a fail on O2 Sensor and Catalyst??  Heated O2 sensor comes back as Pass.  I don`t actually know what the readiness test is.  But does this mean my O2 sensor and Cat are f00ked??

Sounds like the cat is up the Swanny bud.

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Do I need one of these ?

http://www.ebay.co.uk/itm/Skoda-Octavia-1-8-01-05-Type-Approved-Catalytic-Converter-x1-/141226298858?pt=UK_CarsParts_Vehicles_CarParts_SM&fits=Car+Make%3ASkoda%7CCars+Type%3ARS+1.8+T%7CModel%3AOctavia&hash=item20e1be4dea

I`ve been reading up and if you have a fooked cat it's normally due to it being blocked up.  The main symptom of this is loss of power.  I`m not getting any loss of power at all.  In fact the car feels perfectly normal and pulls really hard through the revs.   I`m going to take it back for its MOT tomorrow to see if it was the SAI/N249 and N112 removal causing the over fuelling issue.   My mechanic told me that if it has been over fuelling the Cat might be sooted up quite bad.  So I might put some more cataclean through it too and give it another good blast.

 

I`ve also been told if you don`t put a resistor on the N112 the ECU thinks the SAI valve is open permanently and this will cause over fuelling as the ECU is trying to compensate for the extra air that isn`t there!

Edited 11 June, 201412 yr by sammyhale30

Very few cats collapse and block up. I suspect it'll be the actual cat that's shot ie it's not very efficient and not doing it's job. Not sure if the deletes effect emissions but worth ago.

Should always fit resistors to the connectors keeps the engine management system happy. Only code I've had since the deletes and decat is combi valve incorrect flow this can only be cured with a remap I've been told.

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