Emissions Problems AGAIN!!!!

[wlsmith]

Evening...

MR2 has its MOT due towards end of April, decided to stick it on the emissions tester and see how it did as I have had previous problems with this last year.. Anyway it has failed on emissions again... Parts I have replaced are as follows:

1) Lambda Sensor
2) Catalyctic Converter (Non genuine unit)
3) Coolant temperature sensor
4) Exhaust was blowing where non genuine cat was fitted as there wasnt a fitting kit available, so the cat has been welded on at the join to stop the exhaust blowing.

However it still fails emissions on lambda and overall CO2... Im getting to the point now where im feeling I should get rid of it as I have absolutely no idea where to go with it now!, the car is a Rev 3 NA UK Spec!

Kind regards

Will

[Quigonjay]

is the car giving any error codes mate?

[Peter Gidden]

What were the emission figures?

[Nails]

What kind of state is the serviceable items also as not mentioned?

[wlsmith]

Emissions figures are as follows:

Fast idle test - FAIL
CO - Max .30% - 0.30% - PASS
HC Max 200PPM - 30PPM - PASS
Lambda - 0.97 - 1.03 - 2.05 - FAIL

Second fast idle test
CO - .21% PASS
HC - 17ppm - PASS
Lambda 1.02 - PASS

Natural idle test

CO - Max 0.50% - 1.61% - FAIL

Airfilter hasnt been changed for over a year, also Havent changed rotor arm or dizzy cap but getting no running problems

[wlsmith]

I also have a fault code 2 5 stored in the memory as well?

[wlsmith]

The fault code was previous for when I replaced the coolant temp sensor.. I did not clear the codes and carry out a reset which I have just done... I put the car back on the emissions tester and got the following result:

Fast Idle Test
CO 0.93% FAIL
HC 108ppm PASS
Lambda 1.04 FAIL

Second fast idle test
CO 0.69% FAIL
HC 48pm PASS
Lambda 1.03 PASS

Natural idle test
CO 0.70 FAIL

I did notice a kind of chuffing noise coming from the engine when it was idling? Would this be possible misfire? It only happened when I reset the ECU. I warmed it up to operating temperature and revved it up before I put it on the emissions tester but it is still doing this chuffing noise now on idle.. I checked the fault memory again and now I have no codes!

[BenF]

'Chuffing' noise sounds like a small crack in the manifold or exhaust pipework somewhere - that would throw off your Lambda, and if before the Oxy sensor it would also mean the ECU would 'see' more oxygen in the exhaust than it expects.

With the engine / exhaust cold, if you can get your hand near the exhaust manfold ( obviously, you've got only a minute or so before the exhaust gets too hot to safely do this ) you may be able to feel 'puffs' of exhaust gas leaking from a specific place on the manifold - or you may also be able to trace the general location by sound, but can be tricky in the noisy engine bay.

I'd take a very close look at where you've previously welded and make sure there aren't any cracks there.

[Super_red]

Not MR2's but MGF's, these have terrible trouble passing on emmissions when a non genuine cat is fitted. Other things to try are change the air filter and remove your oil to inlet manifold crank case breather, vent the crank case to atmoshpere and block the hole in the inlet.

[wlsmith]

exhaust and manifold check out to be ok! the only leak was round the cat join which has been sorted.. the engine appears to shake slightly whilst it is making this noise? im guessing its not running so good but i dont seem to notice any performance problems through normal driving?

[Nails]

I'd change the airfilter, my experience with induction kits on mr2s they seem to get dirtier quicker than front engined cars although I don't know what the standard setup is like. what about your sparkplugs aswell? Cheap to replace if you have done them. Start with the simple Stuff

[Rob66]

Hi Will

I had the exact same thing at the end of last year, ended up having to get a whole new exhaust system to get it too pass and even then apparently only just. Good luck with it.

Rob

[wlsmith]

Just an update with this.. went to use the car last night.. had left it at least 24 hours or so and it really struggled to start... was quite cold out.. it turned over but didnt fire up.. kept cranking it then eventually it sounded like it was going to start and then it did, although the idle was very irratic and the engine seemed quite lumpy.. would this be related? I'm thinking dizzy cap, rotor arm, new air filter & set of plugs?

[Kinsy]

It might be weak spark due to a cracked coil. The recent cold snap tends to kill them off as moisture gets in, freezes and then dries out. Take it off and check it over thoroughly, any cracks - replace.

A good service is a bit of a no brainer - whip off the dizzy and rotor and check condition! Check your plugs are clean and properly gapped too, and change that air filter - shouldn't be too dirty after a year or so.

Doesn't really explain the lambda though - does a high value mean there's a leak somewhere letting exhaust gas out?

There is another way...find a friendly MOT tester

[garry goodall]

was the lamda sensor you replaced a genuine part? I replaced mine the other week with a non genuine one and it was faulty showing, done a reading via the diagnostic port and it shown that it was constantly giving a rich reading regardless of engine speed or temperature.

might be worth a shot (genuine or not)

if you have a multimeter.

warm engine up to operating temperature, then hold the revs at about 2.5k

test between ports in the diagnostics plug - VF1 and E1

if the sensor is ok you will see it fluctuating between 0v - 5v quite quickly, if the reading is either 0 or 5 volts constant or the reading is very slow to fluctuate the sensor is most probably broken and will need replacing

[garry goodall]

just to add as mine was stuck in the rich position the car was extremely hard to start and spluttered quite a lot, much like your symptom above

[Peter Gidden]

if the sensor is ok you will see it fluctuating between 0v - 5v quite quickly

Assuming it's a narrowband, it'll flutuate between 0 and 0.8V.

ETA

No hope of narrowing down the problem until all service components can be ruled out. Plugs, cap, and rotor arm should all be replaced regularly as part of routine servicing.

[garry goodall]

thought all 02 sensors were narrowband?

just going by what is says in workshop manual for 0-5v

[Peter Gidden]

thought all 02 sensors were narrowband?

just going by what is says in workshop manual for 0-5v

Narrowband (i.e. OEM) 0 - 0.8V
Wideband 0 - 5V

Looking for 8 fluctuations in 10 seconds.

[garry goodall]

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