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The mkiv Supra Owners Club

MoT test question (emissions)


Jake

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My VVTi has failed it's MoT test on emissions. The printout from the "Johnson Controls Ultima Gas analyser" shows the following :

Fast Idle Test : ...FAIL

Engine speed: ......NOT CHECKED

2350-2650rpm .......----rpm

 

CO:

.....0.77%vol ......FAIL

 

HC:

......45ppm.........PASS

 

λ : 0.970-1.0303

....0.998 ..........PASS

The car has had the front cat removed but still has the second cat fitted. I don't have the front cat, it snapped.

 

I've seen post on here where folks were saying these imported Supras shouldn't have a cat test but the MoT guys say it says on their computer that it does have to have a cat test. Are they correct?

 

 

At the moment I'm waiting for the car to cool down enough for me to take the Lamda sensor out for cleaning. What can I do to get it through the test?

 

Thanks

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Hi Jake

 

That's a bit of a bastard :(

 

Personally, I'd change the lamda sensor and try it again.

Make sure that the car is really hot before you stick it on the meter.

If that doesn't work, maybe try to borrow a 2nd cat from someone on here, there's got to be a few floating about :D

 

It should pass OK with just one (2nd) cat. Maybe yours is a bit weak, but as I say, stick a new lambda sensor on first, for £50-60 it's got to be worth a try ;)

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Just out of interest Jake where did you take your cars for MOT? I used to use a garage in Southsea for my gf's old banger, but a bit of a back street operation and it's changed hands since... can you recommend your place..?

 

Do they know what their talking about with Supra's? not going to 'create a problem' to get some business....?

 

Hope you get the emissions sorted... don't know how you run two of these things! ;)

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Just out of interest Jake where did you take your cars for MOT? I used to use a garage in Southsea for my gf's old banger, but a bit of a back street operation and it's changed hands since... can you recommend your place..?
Hi mate,

I always take our cars to Sycamore Cars in Emsworth. (The first Texaco petrol station on the road from Havant to Emsworth) Their number is 01243 377755

 

Do they know what their talking about with Supra's?
Nope! :p

I only use them for MoT tests. They're good for those because they don't get silly over things. They've never failed a car of ours for anything I didn't agree with.

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Jake,

 

Although it was on my Subaru, that CO figure is roughly what I saw when it failed its MOT on emissions grounds.

 

The car had a high flow sports cat in the centre section, but nothing in the downpipe. At the time of the MOT, it was suggested to me that the cat may not be performing to its full efficiency either through a manufacturing defect or simply because it wasn't getting hot enough being further away from the turbo than the downpipe cat would be.

 

Given that a Supra normally seems to pass on the centre cat alone, it may be that perhaps yours is not performing as it should in the light of that CO reading? However, having said that, I would have thought that a cat of that age would still be up to the job.

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My VVTI failed the first MOT as the result of a faulty Lambda sensor.

 

But the emissions were way out.

 

CO was 8.6 , HC 294 and Lambda 0.749 (very rich)

 

 

 

It passed the re-test with a new Lambda sensor.

 

The HC and Lamda values were very close to what you got.

 

For the CO value I got 0.073 compared to your 0.77.

 

I had both catalysts in place.

 

Looks like your Lambda sensor is working okay, if it's faulty it would make the mixture richer to prevent damage to the engine.

 

The catalysts will convert poisonous CO to less harmful C02 .

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Nope. Failed again. Readings about the same or worse than before I changed the plugs, air filter and cleaned the Lamda sensor. I get the engine really hot before the test. Even tried resetting the ECU

 

I don't know what else to do now.

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Jake, can you try the lambda/oxygen sensor from your other Supra, or is it different on the VVT-i?

 

The oxygen Sensor detects the relative amount of oxygen that remains after combustion in an engine. The oxygen sensor is electrically connected to the on-board computer, which interprets the signal and adjusts the air-fuel ratio as necessary. If it's faulty it can allow the engine to run rich with too high CO levels.

 

Sometimes, when testing, increasing the engine speed up to the maximum allowed, (for the test, not redline :D) about 3000rpm IIRC, can bring the CO levels down enough to get a Pass.

This depends on whether the tester is friendly enough to fcuk about in order to massage it through ;)

 

IME emissions test failures are nearly always oxygen sensor (prime candidate) or the CAT.

 

If the cat worked OK last week, the chances are it's still OK now.

 

Unless the car is running like a pig, it's unlikely to be ECU/injectors or the like.

 

Gutted for you over the wheel mate, it's just not your day :(

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