MOT failure CO2

[Aspire]

Hi Guys,

Car failed on emissions even though it is dual fuel, tried it on both fuel systems seems that to be the air flow meter. When you disconnect it sometimes the engine dies sometimes doesn't and the sometimes the co2 alters sometimes doesn't, checked for air leaks etc cant find anything checked spark plugs they correct colour etc. No dash lights on cant think of anything else what else to check and how?

Regards

Simon

 

[jcasey007]

what were the MOT emissions readings for petrol and gas?.

BTW the air flow meter is not used by the gas system

 

[janolsson]

New plugs, air filter and oil+filter can make a big difference
If you have the facility you could read the ems and see if there are any stored codes. If not then everything is working as it should and could point to the cats. (I am right in thinkin the o2's are pre cat aren't i, been a while since i was under the ex and just finished a 14 hr day at work)
If the emmisions are marginal then the tune up could tip the balance. Also make sure you rag the old girl for a good drive so the cats are hot before you go in for the test and make sure that if the car is rested for 15 mins b4 the test then the tester runs some revs for a minute or so before the gas test.
My money is on something is not quite right as mine passed with flying colours with f***ed up chain guides
regards

 

[Aspire]

Readings on gas 1.02 % on petrol 1.54% changed air filter in process of oil change will regap plugs as they only done 15k and are platinum. Put cat o clean through and went up motorway for region of 40 miles still well out. Seems that when you pull the maf then no real difference so ordered one and will see how it goes!

Thanks for help

 

[BIGHVM]

have you tried cleaning the maf, its easy to do- remove it and tickle the wire elements with cotton buds soaked in nail varnish remover and let air dry- reset ecu after putting back by taking batt offline for a bit and then have it measured again mate. I have done mine a few times now...hope it helps you.

 

[jcasey007]

Hi Aspire


If it is running rich on GAS as well, it won't be the MAF as it is only used when running on petrol.

what was the Hyrocarbon reading at the MOT as a high reading will indicate unburnt fuel.

cheers

jim

 

[Aspire]

the HC were low around 23, I? have taken out the maf cleaned it etc but didn't reset the ecu. So will do that later today.

 

[jcasey007]

that is low, the upper threshhold for MOT failure is 1800 PPM if I remember correctly. My last MOT readings were 0.1% and 400 PPM on gas.

That you are seeing a rich mixture of about the same on both petrol and gas means that there is a common fault. So look at your Gas system first as this uses less sensors etc than the petrol side.

For example my gas system only shares the following inputs with the petrol side.

Throttle position sensor
1 x lambda sensor
Coolant temp sensor.
EGR system
Ignition coil 12v input (just for gas system activation)

So things like the MAF, cam sensor, Intake air temp, fuel pressure regulator etc will not be the cause as they are unique to the petrol system.

My advice is to check the inputs on your gas (as above) as there are less of them, you have checked the mechanical side? (manifold leaks)etc. What gas system do you have?

cheers

jim

 

[Aspire]

Yes checked for manifold leaks all seem ok,
Ok so how do I test lambda sensor
Coolant temp sensor
EGR system
seems that I do have a strong output from the coil.

And where are they to be found?

Regards

Simon

 

[jcasey007]

Hi simon

the best source of pictures and testing of these sensors as a starting point is the haynes manual (I don't believe I have just written that ) coupled with additional searches on the forum.

Test and eliminate the easier to test which would be (IMHO)

coolant temp sensor (test with a Digital Multimeter set on resistance)
Lambda sensor ( tap into the signal lead with a volt meter whist the engine is running)
EGR system, there are quite a few sensors and sub systems to check on this one but at idle I'm pretty sure the EGR valve should be shut.

If you search the forum for each there will be some very good posts with pictures.

cheers

Jim

 

[janolsson]

If it's running rich first point of call would be coolant temp sensor. It may be off and therefore you're ecu thinks its running cooler than it is and therefore adds more fuel (like the old days when you had to use the choke until the car warms up).

 

[jcasey007]

make sure you test the correct one as there are two located close together. one drived the guage, one drived the PCM.

I think it is the grey one that is the PCM one to test (but it has been a while since I looked)

 

[Aspire]

finally went through, the system is a single point gas changed oil and filter and the MAF re gapped the plugs and through she went.

Thanks for the help

 

[janolsson]

Well done mate