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MOT Emmisions Fail - Help!

Discussion in 'A4/S4 forum(B5 Chassis)' started by mal79, Jan 15, 2012.

  1. mal79
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    mal79 Member

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    That time of year again, yes MOT failure time - the joys of 1.8 n/a ownership..! This year it failed on o/s CV boot and emmisions. After refitting the driveshaft for the second time (don't ask!), I think I am now sufficiently warm to turn my attention to the emmisions side of things and am hoping you guys can shed some light on this.

    Anyway, first off the emission results:

    Fast Idle Test @ 2729rpm
    CO level= 0.64% FAIL (0.30% max)
    HC level= 34ppm PASS (200ppm max)​
    Lambda= 1.01 PASS (0.97min-1.03max)

    Second Fast Idle Test @ 2659rpm
    CO level= 0.57% FAIL (0.30% max)
    HC level= 43ppm PASS (200ppm max)​
    Lambda= 1.15 FAIL (0.97min-1.03max)

    Natural Idle Test @ 869rpm

    CO level= 0.37% PASS (0.50% max)​


    The car was well overdue a service so have replaced oil, plugs and filter. The old plugs, oil and filter were nearly 2.5 years old, and pretty grubby. I had also had the pattern part coolant temp sensor issue up until last March, so there has been a fair amount of over-fuelling going on in the past.

    I also took the opportunity to invest in a cheap cable and VCDS Lite to check what fault codes are being thrown:

    3 Faults Found:
    17967 - Throttle Body (J338): Fault in basic settings
    P1559 - 35-00 - -
    17967 - Throttle Body (J338): Fault in basic settings
    P1559 - 35-00 - -
    17916 - Idle Control Sys: Upper Regulation Limit Reached


    I'm not sure why the first code was repeated twice, but after clearing it only comes up once now (but comes straight back)? The "idle control sys" fault comes up when ignition is on but haven't started the engine - if I clear it when engine is running it doesn't come back on. Any ideas on these fault codes?

    I also had a go at logging some data to see if I could find anything that looks unusual. I got "TB angle", "Ignition timing" and "Mass Flow" though couldn't seem to find where lambda values would be. At idle of 840rpm TB angle= 6.9-7.4 deg, Ignition timing= 9.8 beg BTDC, Mass flow= 2.92-2.98 g/s. Values seem to increase with RPM as you would expect. Any thoughts on these figures?

    Thanks guys
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  2. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    I had a similar TB code which was caused by some corrosion in the plug. I removed it and sprayed some WD40 around then replugged it a few times and it went away.

    Looking at the figures, i'd have said the cat was worn out or missing.
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  3. mal79
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    mal79 Member

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    Sadly the car is absolute bog standard, ADR engined slowness! The cat is still in place, as are both lambda sensors. No faults coming from the lambda's, so if the cat was failing, would I not be getting fault codes from the second lambda?

    I am wondering about the throttle body. As far as I know it has never been cleaned, and with 180k + on the clock, must be filthy. Perhaps I will whip this off and have a look...
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  4. S4_dan
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    S4_dan Fire up the Quattro!

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    If its been overfuelling and putting neat fuel into the exhaust that will slowly deteriorate the cat. Try using CATACLEAN. Its about £15 a bottle but it DOES make a difference! I've used it a few times with good results.

    Always worth a shot at cleaning the TB. Its very easy to do.

    Dan
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  5. mal79
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    mal79 Member

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    Well the deadline for the MOT retest is tomorrow, so booked it in for first test of the day regardless. I'll keep my fingers crossed that the plugs/oil/filters will improve things a bit. I'll also make sure the climate control is off this time in the hope that less drag on the engine from the failing compressor allows less fuel to be burned/ converted to CO... At the very least I'll be able to see what impact these actions have had!

    With regards to the fuel additive, I'll save myself £15 and instead put it towards whatever I need to replace after tomorrows retest! I think the last time I used an additive was Redex in an 850cc Mini City back when I first started driving. A "clean" engine was the least of my worries with that car...:sob:

    Anyhow, tonight I was going to look at the Lambda measuring blocks in VCDS Lite. Thing was the cheapo lead didn't seem to want to play ball tonight, losing contact with the controllers when I actually started the engine. Perhaps I'll try and persuade the MOT tester to check the emissions with just the ignition circuit on! I think I need to play around with VCDS a lot more, in the daylight and with a full battery in the laptop.
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Only later cars had a second lambda, so yours may not have one.

    Give it a thrashing on the way to the test station ;)
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  7. mal79
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    mal79 Member

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    Is that the "B5.5" models then? TBH I haven't bothered to check how many plugs I have at the bulkhead,

    2nd and 3rd gear WOT - one of the few joys of n/a engined motoring! You forced induction guys don't know what your missing :lmfao:
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Afaik just some late facelifts got the second lambda.

    I drove a 1.8 vectra the other week, so i know all about what your missing :p whats funny is that when driving normally, round town etc, it didnt feel that different, its just that once you reached about 25% throttle you discovered the rest of the pedal travel doesnt do anything :p
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  9. mal79
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    mal79 Member

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    It passed! Tester advised that it took a long time to "get warmed up" for the emissions to fall - he was testing it for about 30mins and I had been driving it for about 25 mins prior to that. I assumed he was referring to the Cat getting warmed up; coolant was well up to temperature, oil was just above 80deg on gauge (it was close to 100deg after test though).

    Unfortunately I didn't get a print out of the emissions test this time, so don't have hard figures to go on. If the tester was using his discretion, prehaps that is a good thing... However that still leaves me with a problem of what needs doing next as nearly an hour of the engine warming up to meet emissions target is not right.

    If the cat is taking a long time to warm up, I guess you are correct and Cat is on way out. Past overfuelling has probably meant that fuel has been burned in the Cat damaging the matrix. I think I will replace the Cat and get it gas tested again for peace of mind.

    I know what you mean. Back when the 2nd gen Focus ST came out I had a drive in one. My daily driver was a 1.8 Metro GTi and I remember thinking that the ST wasn't that quick at all. Then I used a bit more of the pedal than I usually did... :undwech:
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  10. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    The cat just gets tired, and once tired needs to be really hot to actually work.

    The problem is that hes probably left the car idling for a while as hes checking other things, so the cat cools down. As part of the emisssions test he'll hold the engine at say 3000rpm to get the cat back up to temperature. A new cat probably wouldnt need that at all, but as they age they need longer and longer at 3000rpm to get enough heat into the cat to get it converting properly.
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