MoT Failure - HC Emissions
Discussion
I've had the Chim for about a year now. It was MoT'd just before I bought it, and it's just had it's first MoT under my ownership. Everything was OK except the HC emissions, which was way over the limit. The limit is 200, and it was generally fluctuating around the region of 400-600, though would go up into the 2-3000 range at 2500rpm. Admittedly the engine is a bit lumpy on tickover, but it's not really that noticeable and it still goes very well. I've taken the plugs out in the hope that one would be a different colour, but they all look pretty similar. Has anyone else had similar problems, or can anyone suggest probable causes. This is not the weather to be off the road!
S7Paul said:
I've had the Chim for about a year now. It was MoT'd just before I bought it, and it's just had it's first MoT under my ownership. Everything was OK except the HC emissions, which was way over the limit. The limit is 200, and it was generally fluctuating around the region of 400-600, though would go up into the 2-3000 range at 2500rpm. Admittedly the engine is a bit lumpy on tickover, but it's not really that noticeable and it still goes very well. I've taken the plugs out in the hope that one would be a different colour, but they all look pretty similar. Has anyone else had similar problems, or can anyone suggest probable causes. This is not the weather to be off the road!
I've always been told to take the car for a good run before the MOT. Make sure the engine is hot when they test it.Hydrocarbons are are basically unburnt fuel, so even a single cylinder not firing correctly will contaminate the exhaust or its running too rich, and not all the fuels being burnt. If its a bit rich its fine power wise, as to pass the emmissions it runs leaner and below the maximum power point anyway. That lumpy tickover probibly is probibly the effect of overfueling or misfire. How technical do you want to get?
Mark
Mark
The guy at the MoT centre said it was a misfire, which may well be true, though if that is the case I think it's done it since I got the car, as I haven't noticed any difference. The engine shakes a bit on tickover, which on reflection is another indication of a misfire, but I'd assumed they all do that. I'm intending to try a new set of plugs & leads anyway, even though the plugs look OK. Do the plug shrouds (extenders) often cause trouble (as a set of those is quite pricey)?
Resurrecting an old thread here as the same thing has happened to me today, the car failed an otherwise completely clean MOT on HC emissions. It scored a reading of 600ppm, then 400ppm on the second attempt. I will check plugs and leads but is there anything else to do? The leads are a set or Magnecors and nearly three years old, they can't have done more than about 6000 miles though and running on 97RON fuel. Have some owners found these leads to be troublesome?
Also just for information, the engine was fully up to temperature for the test.
Thanks
Tom
Also just for information, the engine was fully up to temperature for the test.
Thanks
Tom
I have had success with with fuel system cleaners, even clearing fault codes,
http://www.dae2008.co.uk/fuel-system-conditioner.h...
If you have a problem with an injector it may just clear it.
Not sure about this, but are just going throw it out there for comment,
Could a blocked air filter lead to a problem? Thinking that at low revs there is not enough air getting into the engine, but works OK when the the vac increases.
http://www.dae2008.co.uk/fuel-system-conditioner.h...
If you have a problem with an injector it may just clear it.
Not sure about this, but are just going throw it out there for comment,
Could a blocked air filter lead to a problem? Thinking that at low revs there is not enough air getting into the engine, but works OK when the the vac increases.
It has had the pre-cats removed but the main cat is still in, my understanding was that it would still get through an MOT like that when all was up to temperature, the other two parts of the emissions lest were easy passes.
After sleeping on it I could believe there might be a misfire I supppse. I'll have a chance to look at it tomorrow...
T
After sleeping on it I could believe there might be a misfire I supppse. I'll have a chance to look at it tomorrow...
T
IIRC a TVR will fail the full test but as a PLG passes a less stringent test.
A thread from 2009 discusses this here (ignore the title)
The pertinent part is this:
As a MOT testing garage and tester I have read the rule book and all TVR's are required to pass an emmision test relating to the age of the vehicle. The rules are; any vehicle first registered on or before 1/8/75 requires a visual test only. From 1/8/75 till 1986; CO% of no more than 4.5% and HC of no more than 1200ppm. From 1/08/1986 to 31/07/1992; CO% less than 3.5% HC less than 1200ppm and basically after 1/08/1992 onwards a CAT test is required with limits of 0.2 CO%, HC less than 200ppm and Lambda between 0.97 and 1.03 at 2500 to 3000 rpm for minimum of 30 secounds then idle C0 less than 0.5%.
However, the TVR range with cats get less stringent requirements; late 'S' models, Chims and Griffs; less than 0.3 CO% less 200 HC and 0.9 to 1.1 lambda reading. Speed 6 and AJP engined cars less than 0.3 CO%, less than 200 HC and 0.9 to 1.2 lambda all at 2500 - 3000rpm for min 30secs and 0.5 CO at idle.
We have found the lambda reading is always the struggle with the standard limits but all will pass with the specific TVR limits as long as CATS are fitted and the cars running ok. There are some exceptions to these rules but generally appling to kit cars and one offs.
Not sure if the regulations have changed since then but I don't think they have. Either way I'd suggest that the tester should have a look at his rule book.
ETA The PDF with the regs in can be downloaded HERE
A thread from 2009 discusses this here (ignore the title)
The pertinent part is this:
As a MOT testing garage and tester I have read the rule book and all TVR's are required to pass an emmision test relating to the age of the vehicle. The rules are; any vehicle first registered on or before 1/8/75 requires a visual test only. From 1/8/75 till 1986; CO% of no more than 4.5% and HC of no more than 1200ppm. From 1/08/1986 to 31/07/1992; CO% less than 3.5% HC less than 1200ppm and basically after 1/08/1992 onwards a CAT test is required with limits of 0.2 CO%, HC less than 200ppm and Lambda between 0.97 and 1.03 at 2500 to 3000 rpm for minimum of 30 secounds then idle C0 less than 0.5%.
However, the TVR range with cats get less stringent requirements; late 'S' models, Chims and Griffs; less than 0.3 CO% less 200 HC and 0.9 to 1.1 lambda reading. Speed 6 and AJP engined cars less than 0.3 CO%, less than 200 HC and 0.9 to 1.2 lambda all at 2500 - 3000rpm for min 30secs and 0.5 CO at idle.
We have found the lambda reading is always the struggle with the standard limits but all will pass with the specific TVR limits as long as CATS are fitted and the cars running ok. There are some exceptions to these rules but generally appling to kit cars and one offs.
Not sure if the regulations have changed since then but I don't think they have. Either way I'd suggest that the tester should have a look at his rule book.
ETA The PDF with the regs in can be downloaded HERE
Edited by V8 GRF on Tuesday 18th November 08:41
I seem to remember cars registered at the end of 1992 might have had a bit of leeway. Ford Sierras, TVR Griffiths and probably some others were registered on a K plate without cats fitted. (Only one reg change per year back then). There was a changeover period depending on engine type / the DVLA database that lasted as long as 1995.
You should not have a problem unless something is wrong. You could always drop all 8 plugs out and look at the colour to see if one is more sooty than the rest if an injector is suspect. Like wise if one bank of plugs is sooty- then you have a misfire on that bank. Problem is TVR plugs are pretty black most of the time anyway, so seeing a colour shift may not be that easy.
OK, so had a chance to start on this this afternoon and did the following...
Checked for a misfire by pulling HT leads off the plugs in turn and listening for a plug that made no difference to the tick over of the engine. All of them seemed to be firing as pulling the leads off caused a rougher idle. I did have a suspicion about No.6, next up the plugs came out...
What do people think about this? I would have thought they should be cleaner than that. And the corrosion on the second from the top (left) and third from top (right), what would cause this? Have they not been properly seated in the block?
When connected to rover gauge the fuel trim is within normal ranges, can i draw any conclusions from that?
What would be your next step? I'm thinking a fuel system conditioner and a 20 mile blast couldn't hurt...
Checked for a misfire by pulling HT leads off the plugs in turn and listening for a plug that made no difference to the tick over of the engine. All of them seemed to be firing as pulling the leads off caused a rougher idle. I did have a suspicion about No.6, next up the plugs came out...
What do people think about this? I would have thought they should be cleaner than that. And the corrosion on the second from the top (left) and third from top (right), what would cause this? Have they not been properly seated in the block?
When connected to rover gauge the fuel trim is within normal ranges, can i draw any conclusions from that?
What would be your next step? I'm thinking a fuel system conditioner and a 20 mile blast couldn't hurt...
Id drop a plug heat grade and go for a 6 to get them to run cleaner- they are running too cold to get any sensible readings. I dont know why TVR run a 7 grade, the original RR engine runs a 6, and to be honest you cant really hold these cars open at high throttle loads for long periods on UK roads when plug heat would be more of an issue- most of the time you are pottering along and the plugs simply dont get hot enough to burn off the carbon.
If you have correct long and short term trim in RoverGauge, Id be suspecting ignition. A really bad misfire will show up as very high positive long / short term trim, but you wont see minor misfires. You need something like an old style crypton tune to look at HT waveforms, but Id start with a new set of plugs first off, although a bottle of catalyst cleaner and a good blast certainly wont do any harm.
If you have correct long and short term trim in RoverGauge, Id be suspecting ignition. A really bad misfire will show up as very high positive long / short term trim, but you wont see minor misfires. You need something like an old style crypton tune to look at HT waveforms, but Id start with a new set of plugs first off, although a bottle of catalyst cleaner and a good blast certainly wont do any harm.
Edited by blitzracing on Wednesday 19th November 19:15
Well, we got through the test today.
All i did in the end was clean up the plugs and get half a tanks worth of fuel system cleaner through it, the tester said it was fluctuating between about 100ppm and 500ppm during testing but it has got through the test so i now have plenty of time to instigate any rich running.
After an ECU reset the long and short term lambda trims looked good, no fault codes and all RoverGauge readings within their expected ranges. I'll have another look in a few weeks to see if anything looks suspect but i expect it might just be the case that TADTS.
Thanks for the helpful suggestions.
Tom
All i did in the end was clean up the plugs and get half a tanks worth of fuel system cleaner through it, the tester said it was fluctuating between about 100ppm and 500ppm during testing but it has got through the test so i now have plenty of time to instigate any rich running.
After an ECU reset the long and short term lambda trims looked good, no fault codes and all RoverGauge readings within their expected ranges. I'll have another look in a few weeks to see if anything looks suspect but i expect it might just be the case that TADTS.
Thanks for the helpful suggestions.
Tom
I had the same problem with mine for the first couple of MOT,s, did the usual things to it, but it hasnt done many miles between MOT,s so worn parts should not be an issue on the third time I went and put plenty of petrol in and it was fine, this was the only common thing I had done and to be fair it was low on fuel every time I took it
Not sure if you are all sorted now, but for reference try and have the engine terra cleaned, just had my Galaxy done and has made a difference to economy and performance.
http://m.youtube.com/watch?v=wiViPKIoG68
http://m.youtube.com/watch?v=wiViPKIoG68
the corrosion you mention is from water.......no really
I had this on my wedge. The HT lead was resting on the body and when it was raining the water ran down the body....across the inner wing........where the HT lead touched the body cause almost a bridge and a trickle of water ran down the lead into the plug well..........car parks for a bit with wet plug wells causing corrosion.........when you drive off it gets warms and dries
My car doesn't go out in the rain so was caused just by washing it
just make sure your HT leads don't touch anything :-)
I had this on my wedge. The HT lead was resting on the body and when it was raining the water ran down the body....across the inner wing........where the HT lead touched the body cause almost a bridge and a trickle of water ran down the lead into the plug well..........car parks for a bit with wet plug wells causing corrosion.........when you drive off it gets warms and dries
My car doesn't go out in the rain so was caused just by washing it
just make sure your HT leads don't touch anything :-)
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