I started a thread about my Daughters punto that failed its MOT on Emissions around a week ago. The car was bought as a bodywork project and hasnt moved off the drive until its MOT. I thought it could be a fuelling problem but it smokes and ive never seen that on overfuelling. I have seen an engine burning oil and this looks like it could be doing just that. The engine has done 77k ive changed the plugs and the old ones were not fouled with oil. Ive also changed the air filter and was about to do the lambda sensor until I saw there are two sensors on the exhaust so I need to find out which I need to change or both.

So my symtoms are it ticks over fine and spits a little bit of soot and I mean tiny bits. Now if you keep reving it hard you get a blueish smoke and lots of it until you back off the throttle. If you let it tick over no smoke, for this reason I suspect worn valve stem oil seals and this would effect the emissions. If anyone agrees or has had the same problem please reply. I dont want to rip the head off and buy gaskets and seals for someone to say its a blocked breather lol.

Ive got the print out of the emissions failure if that helps ???

I possibly agree with you however I would run a Dry and Wet compression test on all cylinders just to rule out leaky pistons seals.

:yeahthat:

Thanks guys and whats the best way to do this ??? wet by a bit of oil in the bores ??? also what reading should i get roughly or am I just looking for equal readings ???

If the bores are good only a slight improvement, main thing is that they are all fairly even both wet & dry..

Plugs out (all of them) do a dry test without oil in the cylinders, 1 at a time & note the results, ensure the battery is fully charged to crank fast & consistently.

Then put a couple of cc's of engine oil in each cylinder 1 at a time & repeat the tests noting results.

A big improvement across all cylinders isnt great, one or two massively different is bad...

Also would add that when compression testing (wet or dry) you need to look at how the pressure rises in the guage. On a normal petrol car then a good 80%+ of the final pressure is reached in THREE strokes/pulses. Strokes/pusles after that add only a confirmation that the first 3 strokes were valid.

I can't remember what psi one should be expecting (depends on engine compression ratio) but 180 to 200 psi with around no more that 10psi difference between cyclinders is in the right ball park.

Right guys ive just done the test and I got roughly 160 lb in across all bores but it shot up over 200 with oil in. I must confess I didnt measure the oil I just added a splash in each bore. I turned the engne over equally for each bore. This was three turns, all plugs out but the fuel will still have been going in.

What do you guys think now ????

When the car failed the MOT did you get a printout of the actual test results?

160 psi is below what would have expected (180) but if you got 160 across all cylinders then I'm thinking that possibly you failed emissions for a different reason.

If the car was burning oil then it would be the HC (Hydro Carbon) levels that could be the cause of the fail. However excessive richness, hi a CO value or a Lambda value out of range could also cause a fail.

I suggest you esptablish exactly what/why you failed.

s130 said:

When the car failed the MOT did you get a printout of the actual test results?

160 psi is below what would have expected (180) but if you got 160 across all cylinders then I'm thinking that possibly you failed emissions for a different reason.

If the car was burning oil then it would be the HC (Hydro Carbon) levels that could be the cause of the fail. However excessive richness, hi a CO value or a Lambda value out of range could also cause a fail.

I suggest you esptablish exactly what/why you failed.

Click to expand...

Give me 10 mins I will add the print out here

Exhaust emissions carbon monoxide content at idle excessive

Exhaust emissions carbon monoxide content after 2nd fast idle excessive

Exhaust emissions hydrocarbon content after 2nd fast idle excessive

Exhaust emissions lambda reading after 2nd fast idle excessive

co level at 2759 rpm 0.88% FAIL no more than 0.20

HC level at 2759 rpm 361 ppm FAIL no more than 200

lambda at 2759 1.09 FAIL no more than 1.03


2nd run

co level at 2759 rpm 0.80% FAIL no more than 0.20

HC level at 2759 rpm 235 ppm FAIL no more than 200

lambda at 2759 1.06 FAIL no more than 1.03


thats all the fails !!!

Initially not looking good, however I see that the second run data was a little improved over the 1st run data.

I would do the following:

1) remove the lambda sensor and thoroughly wire brush the mounting threads clean of all residual dirt, rust etc. BE VERY CAREFUL! Do no touch/clean/brush anything ofther that the mounting thread.

2) if the sensor head is obviously contanimated then gently clean in alcohol.

3) check and clean lambda sensor lead connections

4) phone your local council and ask where their MOT testing station is and phone number. Phone the station up and ask them if they can find you a slot to do a quick emissions check before you submit the car to them for a formal MOT. Most council testing statons will do this as they have an obligation to help the public keep their cars road legal and they understand that some things (like emissions testing / brake efficiency and blance) is not something people can easily check and test (unlike the most of the rest of the MOT requirements) This is/should normally free of charge!

5) Before submitting the car for testing have a good thrash on and open road at 4000rpm plus for as long as possible. Steady high RPM driving flush of the system. Avoid power accelleration or hill climbs. We want hight rpm (= high exhaust flow rate) with minimal fuel usage.

If you then fail discuss the results with the tester. They do 1000's of tests per year and have seen just about every failure you can imagine. They also have no axe to grind or money to make from your failure as they ONLY test and do not make money from repairs.

Hi thanks for that info, ive actually got a new lambda sensort there so I might just fit that. Is it the one lower down the exahust or the one at the top ??? The MOT station blamed the lambda or injectors. The burning oil or should I say the smoke that looks like burning oil doesnt look good. The strange thing is it didnt smoke when we got it and its noit moved off the drive in two months. The smoking came after I changed the plugs

you could try some fuel additive and add some flush in your engine oil, take it for a good run say 15 miles and then change the oil n filter, air filter will also help. check your exhaust system dosen't have any leaks, may be you have fitted the wrong plugs?