Hi,

I just put my 2000 100 sx 1.6 in for its mot expecting it to pass. It failed on emissions and I am not sure what to check. The exhaust is not all that old and I cant detect and leaks. What else should I be looking for.

Thanks

Les.

Stick up a copy of the emissions results and someone may be able to help you

daves way is usually-

put fuel injector cleaner in the tank and take the car out for a good thrashing, really good, to clean it all out, then try the emissions again, might not work but worth a try, cos its cheap.

fuel injector cleaner as stated and a good run.also make sure the car is up to temp before you takie it in for the retest.
new plugs and leads dont hurt if there age is unknown

engine speed at 2777rpm

co level = 0.64% max limit is .30
hc level = 94 ppm max limit is 200
lambda = 1.01 max limit is 1.03

second fast idle test

engine speed at 2791 rpm

co level = 0.46% max limit is .30
hc level = 96 ppm max limit is 200
lambda = 1.01 max limit is 1.03

natural idle test

engine speed 789 rpm

co level = 0.10% max 0.35

injector clearner was recently used so it wont be worth while doing it again, probably some still in the tank if this makes any differance.

Les.

the worst thing it would be is the CAT. but first of all try taking out the sensor on the exhaust manifold (lamda sensor) and wire brushing it off (if it has a large build upon it) this might be making the emissions show to high.

Take out the air cleaner (for the test only)

I was checking for a spark with some old plugs and did not see much of a spark. It was quite dark so I was expecting to see a strong spark but it never happened on any of the leads. is this normal or is the coil faulty. As the coil is £90 (unless someone knows where to get one delivered for cheaper) I dont really want to change it if I dont have to.

Les.

The second run is much better than the first run. Was the engine up to the required temperature?

Give it a good run as said and make sure that the engine is at normal operating temperature before the test is done.

This could be a cat problem. But would need to test the lambda probe first, or try one as it could be this.

Hi, Thanks for all the replys. I think that I will try the cheaper options first. I am still a bit concerned that I did not see much of a spark and hope that a faulty coil hasnt damaged the cat. Going to check the exhaust system clean the lambda sensor and replace the plugs and leads, I cant get the car hot for its re-test as I have to drop it off at 6am on my way to work and the test is late afternoon. So its going to be cold for the test. any idea how much a new cat is ?

Les

I've just had a similar problem with my Brava. Following a year of exhaust problems with the engine running rich all the time the Cat is still in perfect working order. Constant replacement of exhaust bits had broken the lambda sensor, but once it was replaced, it passed first time. In the middle of all this I had a dead coil pack when I first had intermittant followed by permanant loss of performance and misfire. How were the plugs looking? Might be worth replacing if they're a bit mucky, cheap enough to do. Don't even go there with the Cat, they're not cheap as they're full of precious metals

Ok basically the cat was not hot when the test was started. If you check the figures the only one that changes is the Co figure which drops by 25%. The Hc reading shows that the engine tune is all ok as does the lambda reading, ideally this should be 1. The readings obtained are common if you have a jobsworth doing the test, by raising the revs to 4000 rpm you can watch the CO drop suddenly as the cat comes up to temp and starts to clean the exhaust gases. Observe the test next time and make sure that the tester gets the engine upto temperature properly and ask him to rev the engine when hot to 4000 rpm before he carries out the emissions test.

I've had another look at the emissions and am not 100% on the read out.
The cat not being up to temperature ref previous responses would be a reasonable explanation but I don't know of any tester that would not get the engine and cat up to temperature first without good reason. It's certainly worth challenging them but I have the following observations on the readings:-
1) The lambda reading is exactly the same on both runs - there should be a little fluctuation in this reading. The lambda is normally read to 3 decimal places to show this fluctuation.
2) The hydrocarbon reading seems very high for an engine in good tune. My Sie Sporting achieved 27 - in fact it also achieved 0.058 CO% on an engine that was not allowed to warm up fully as the alternator had packed in and we didn't want the battery to go flat during the test (I didn't want to cancel the test so took the risk knowing the engine was in good tune and I wouldn't have an opportunity to get it tested for another week if I missed this slot)

I believe the engine is running rich (you haven't wired in one of those resistors to the AFM have you?) which is why I recommended taking the air filter out before presenting it back for test (old school tricks that have limited success with modern engines) Have you taken out one of your plugs to check the colour? Cleaning the lambda sensor has already been recommended and you can test it with a multi meter and should see the signal to the ECU fluctuating.

I have checked the exhaust system and it seems to be in good condition. Took out the lambda sensor and gave it a good clean. Dont even know what an AFM is so no I havent put in a resister. If the engine is running rich what should I be looking for.

Les

HC reading is not high at all, a rich mixture would result in HCs of 800 plus, easy to prove if the cat is working, do a four gas analysis, Co should be below 0.30, HC below 200, CO2 above 15% and Oxygen as low as possible typically below 0.30. The higher the Oxygen reading the less the cat is working.

Hi,

The car was in for its test today and it passed. The results are a lot different from the first test. I have noticed that the limit for the CO level is not the same as the first test. Is it possible that the test was not carried out correctly/setup correctly the first time. Also the natural idle engine speed looks a little fast to me.

engine speed at 2843 rpm

co level = 0.13% max limit is .20
hc level = 56 ppm max limit is 200
lambda = 1.00 max limit is 1.03

natural idle test

engine speed 1327 rpm

co level = 0.27% max 0.35


Thanks for all the replys.

Les.

Did you ask the tech to make sure she was well warmed through?

I was at work during the test.

Glad it passed. It could be a number of things, but since you cleaned lambda it seems to have done the trick. For the mot the car should have been warm first, if not the mot garage has not done the mot right in the first place. I hope you did not pay for a retest if that was the case.