Anyone able to interpret MOT emissions data please?

hello

so i just got back from the MOT, passed nicely

BUT i'm curious.

ive always known my car to be thirsty, just sometimes i cant believe its as thirsty as it is. and when you run it in the workshop your eyes sting after a few minutes.

so i've got the emissions data from the last few years and wondered if anyone might take a look at it?

on a side note, i started working heavily on the car in 2010, so it's 2010 results could have been particularly good due to new ignition parts etc.

anyway.

2008 HC - 206 ppm, CO - 0.71 %
2009 HC - 251 ppm, CO - 1.15 %
2010 HC - 204 ppm, CO - 0.38 %
2011 HC - 512 ppm, CO - 0.14 %

Im pleased that the CO is lower than ever by quite a long way, but cant understand why HC has doubled, even though the car gets more use now than ever.

It is a 92 Disco 3.5 EFi non-CAT model.

Any information on the subject would be appreciated!!

Cheers, Sam.

hi hc hydro carbons is done to unburnt fuel ie weak ingnition system timing or spark .low compression,worn engine,faulty air input ie air leaks and airflow meter

so seeing as it appears to run very well at the moment, i wonder why the HC levels have doubled?

i wouldnt blame a weak ignition system particularly as it doesnt misfire and copes with water very well - even muddy water at the weekend ony offered a splutter on a few cylinders for a few seconds.

high HC levels could be burnt oil, but again it never smokes, not even flat out revving up to 5500 made it smoke (according to my mate behind me)

the onlyguarantee is that there is plenty of unburnt fuel, becuase it sure is stingy on the eyes.

anyone else got any data to compare with?

cheers

For my 97 3.9 with cats.
2000 HC - 22 PPM CO - 0.01 %
2001 HC - 0 PPM CO - 0.00 %
2002 HC - 12 PPM CO - 0.00 %
2003 HC - 1 PPM CO - 0.00 %
2004 HC - 17 PPM CO - 0.03 %
2005 HC - 12 PPM CO - 0.00 %
2006 HC - 8 PPM CO - 0.00 %
2007 HC - 12 PPM CO - 0.00 %
2008 HC - 13 PPM CO - 0.00 %
2009 HC - 12 PPM CO - 0.01 %
2010 HC - 11 PPM CO - 0.00 %

I'm now off for a beer Dude

Mr Noisy said:

so seeing as it appears to run very well at the moment, i wonder why the HC levels have doubled?

Click to expand...

'Cos its running a bit on the rich side of normal?

but why o why? the efi system doesnt have a mixture screw!!

Mr Noisy said:

but why o why? the efi system doesnt have a mixture screw!!

Click to expand...

Well Chief Dude perhaps you should have the engine ECU read, a sensor may be faulty and giving some wrong info.

How does it start from cold?
I thought those reading were a little low for the age of vehicle. Running lean would also hurt eyes

hi chaps

i went through all the sensors last year, and everything was giving the correct outputs. obviously something might have changed recently!

john, it starts and runs absolutely spot on. cracks straight up without a hint of trouble, hot or cold. the car gets heavy off road use and plenty of motorway no running problems at all.

if anything i find it lacks grunt in 5th gear at low revs, but i put it down to raised gearing and rolling resistances. there is a good amount of soot in th exhaust, not more than i would expect though. no residue on the bumper or anything, and the plugs have always been sooty but healthy looking.

it has noticeably more low end torque when it is cold than when it is hot. ie at 20-40 mph it will pull noticeably harder when it is below operating temp.

for instance, got it out of the garage and took it for MOT, felt pokey.

bringing it back from MOT it was toasty hot, ambient was warm, throttle pedal felt soggy and unresponsive.

this is normal for me though, and i put it down to the intake air temps.


any ideas from that lot of waffle guys?

cheersin advance if anyone comes up with anything!!

ok so a little bit of research suggest that high HC levels are usually due to misfire, high CO lovels are usually due to rich mixture.

so it seems that the engine is running ok, or lean as john suggets, but it is/was mising slightly, whih caused not smoky emissions (CO emission) but completely unburnt fuel in the exhaust.

has to be said if you hold the revs between 1000 and 3000 it pops and bangs in the exhaust. it feels like its missing, but if you get close to or touch the engine you can feel it is running smooth, its just exhaust pops.

i also understand that high HC can be due to oil getting into the exhaust, but it certainly doesnt get oily in the tailpipe and there is never any smoke out the back of it.

hmmmmmmmmm.

genuine cap leads and rotor first and some ngk plugs for starters.
what is the maf reading have you a lambda for the gas or is it open loop?
yes there is a co screw for the 14 cux system

hi mate

it hasgen cap and rotor, good leads and recent ngk plugs.

i checked the MAF output a few months back and it was within spec (i forget what it was) and the car does not run gas, it is open loop petrol.

i know there is a screw on the AFM which could potentially adjust mixture across the range, probably could do with a re-tune after 19 years!!

what do you make of the readings stu?

cheers

Hc`s can also go up due to an air leak. A good way to find out is have engine running then spray easy start or wd type stuff everywhere and see if engine note changes. If it does, start localising spray to locate fault.
Good luck
P.S
Best overall solution is buy a proper car instead (on a defender this is a character trait not a fault)
:boink:

cheers john, very funny

i checked my air system just recently to make sure the snorkel was still sealed. gave it a vacuum test, rag over the intake etc. there was plenty of vacuum and no hiss, so i assume no air leaks.

worth checking it over again just in case.

cheers for the carb cleaner hint

Points of interest
1 how many miles has it done?
2 is the breather system clean and no heavy deposits in the throttle housing?
3 is the timing correctly set
4 are the plugs correctly set?

Ok let's start at the top emissions should be set to 1.0% at idle with a warm engine.

Possible causes worn cam,sticking valve or a lazy follower

hi mate

its done 120000 miles

yeah the breathers are clean (recently had a full clean out, HEAVY deposits in the rocker covers and breathers, now it runs very happily without buildup)

the timing is set to 6 degrees BTDC, and the plugs are gapped correctly.

cheers

Your engine is running a bit lean (weak) that's why your HC's have gone up, as James said HC's are unburned fuel if an engine runs to lean it can't burn what little fuel it has properly causing HC's to go up.

You need to find out why it is running lean as this can cause a lot of expensive problems including burnt valves as the combustion chambers and exhaust will run hotter.

I don't know what the Co. should be but an educated guess would be a bout .7 - 1%

Ragtag said:

'Cos its running a bit on the rich side of normal?

Click to expand...

It's running on the lean side of normal actually

I will take a plug out and see how it looks. Must admit I am VERY surprised to hear that it could be running lean.

I definitely do not want it running lean though!

I wonder if that is why it pulls harder when it is cold - because it is on choke/cold start and therefore runs richer...?

Ill get a picture of a plug.

Cheers!

Cheers.

Take all the plugs out,I think you have a partial misfire which you cant hear/feel. Scoping the plug leads would show it up in seconds,it might be enough to show a darker colour on the plug tip..