NCT failed me on emissions the GOWLS!!

[mcfanta]

Right lads took my 95 mx5 1.8 for a nct today. Passed everything but for emmisions. Now it does feck all milage as its only a second weekend to so that may be the cause. The results were

Low idle @850rpm CO 1.00% and HC 184ppm.....................above 0.50% is a fail and above 0 ppm is a fail

High Idle @2720rpm Lambda 1.00 CO 0.72vol% and HC 67ppm............not between 0.97 and 1.03
above 0.30% is a fail
above 200ppm is a fail

What ye reckon a bottle of stuff and put a few miles on it or could it be something else?

[93 Mk1]

It could be one of many reasons. My NA failed earlier in the year for emissions too. The tester reckoned it may have been a dud plug wire
or a plug itself. A compression test showed that cylinder's 2 and 3 were very low....it turned out that my block had cracked ! I had to get a
replacement motor from Robert. But I think my case was an exception rather than a common MX5 problem.
Did you check things like plugs and air filter ?? If you think additive will cure then I would highly recommend Dipitane. Definitely worth a shot.

[mcfanta]

I replaced the plugs when i got home for a new set. They looked a bit old but not bad. Someone was telling me it may need a new cat but im gonna put a few miles on it and see how it gets on. I put a bottle of lucas stuff into it. Might look into Dipitane tho. Cheers

[MX5Spares]

Full bottle of Dipethane when below quarter on gauge and clean air filter should help

[aquarian5]

yes I always use the Dipithane too , my readings have always been low after using it.
I would also suggest a fresh oil change definitely helps too.


John.

[mcfanta]

I only servised it 2/3 weeks ago and i through in a bottle of lucas to a quater of a tank. Ill have that burnt out in 2 days and then ill through in a bottle of that stuff yer talking about and see. Re test in 2 weeks so will get plenty road by that time

[sidewaysreilly]

Any holes in the exhaust? High co means she is running rich or the cat is fucked. Lambda 1 means injection is spot on. Must be cat.

[mcfanta]

No it has a new hks system with the cat still in it. Anybody ever try TerraClean? I see a garage in limerick do it hmmm

[sidewaysreilly]

You can try all the stuff listed and they may get you through the test but the problem is still there. What are the Plugs , Plug-leads and Coils like? High HC's could be a misfire but high CO and HC is too much fuel .

[MX5Spares]

We have good used cats if you need one but 3 different lenghts something like 375mm ,400mm ,475mm maybe??Cant remember exactly but only the correct lenght fits without welding etc

[mcfanta]

Put it through the test again and guess what??? Went down on emissions again. The Dipithane didnt do the trick. Id say she needs a cat

[Johnny]

I had same problem last year, see post http://mx5ireland.com/forum/viewtopic.php?f=8&t=7290
Used cat from Robert sorted it. I still think the car is running a bit rich as changed plugs last week and they are sooty black (dry) and white smoke from exhaust on start up which goes away after a few minutes of driving. Emissions were very low on the retest after getting cat welded in so it will be interesting to see what they show up at after a years driving when I do NCT in Feb next year. On a side note, what are the other tell tail signs that your car might be running rich?

[93 Mk1]

I had same problem last year, see post http://mx5ireland.com/forum/viewtopic.php?f=8&t=7290
Used cat from Robert sorted it. I still think the car is running a bit rich as changed plugs last week and they are sooty black (dry) and white smoke from exhaust on start up which goes away after a few minutes of driving. Emissions were very low on the retest after getting cat welded in so it will be interesting to see what they show up at after a years driving when I do NCT in Feb next year. On a side note, what are the other tell tail signs that your car might be running rich?

Running rich will or may cause fouled/wet plugs, rough idle and sometimes you will be able to smell petrol from the exhaust fumes.
Excessive fuel consumption can be another hint.

[Johnny]

One Year On:
A year on since I replaced the CAT with used one (from Robert) due to NCT fail last year on sky high CO emissions. Had this years test this morning and car passed again with little or no CO emissions (seems almost too low). I was interested in seeing what the readings would be a year on as if they were back up high again then it was a problem elsewhere causing the CAT/CO emissions problem. Didn't use dipetane or any other stuff during the year and drove it a good bit. From the test readings below the CAT is still doing its job. However, the lambda reading has gone from 1.00 to 1.03 since last year and as 1.03 is the upper limit it didn't need much more to fail.
As far as I know high lambda means too much oxygen/air getting into the exhaust system or a faulty Lambda/oxygen sensor. So I have low emissions and a high lambda. Would this mean that the exhaust fumes are being mixed with air after it passes the lambda sensor by a hole in the exhaust, as if air was getting in before the sensor would it be detected by the sensor and make the engine run rich, which could cause an increase in the CO readings and a decrease in the lambda reading. I don't know? Is the blocking the tail pipe with a rag method the handiest way to check for an exhaust leak? Any suggestions?

Anyway happy days, car passed for another year.

Engine/oil temperature 48 c

Low Idle CO 0.00 vol% - Pass (above 0.50% is fail) - 0.0% CO ???????
(800 rpm) HC 7 ppm - N/A

High Idle Lambda 1.03 - Pass (between 0.97 and 1.03 is fail)
(3040 rpm) CO 0.01 vol% - Pass (above 0.30% is fail)
HC 7 ppm - Pass

[MX5Spares]

Good man Johnny.Moylough,s best driver....and show organiser.!!

Check for exhaust leaks by blocking the tailpipe and listen for leaks/blows