MOT missions fail

[Charless]

I recently failed the MOT on fast idle with a '99 MEMS2J VVC which is bog standard original fit bar an unidentified SS exhaust fitted this year after the OEM one fell apart.

I was expecting to find an air leak when I took the lid off but nothing presents as obvious, no leaking gaskets or damaged lambda wires.
My next move would have been to pick up a new cat from ECP today but they don't show them for Fs any more. The car is booked in for some wheel bearing and bush work at the MOT garage on Tuesday and it would have been good to get the retest done at the same time.
Has anyone any thoughts about the High CO/low Lambda symptoms?
Could a shot cat cause the low Lambda? Or a duff Lambda screw the mixture beyond the cat's control?

[NigelOBB]

I recently failed the MOT on fast idle with a '99 MEMS2J VVC which is bog standard original fit bar an unidentified SS exhaust fitted this year after the OEM one fell apart.

KJS emissions fail 161120.JPG

I was expecting to find an air leak when I took the lid off but nothing presents as obvious, no leaking gaskets or damaged lambda wires.
My next move would have been to pick up a new cat from ECP today but they don't show them for Fs any more. The car is booked in for some wheel bearing and bush work at the MOT garage on Tuesday and it would have been good to get the retest done at the same time.
Has anyone any thoughts about the High CO/low Lambda symptoms?
Could a shot cat cause the low Lambda? Or a duff Lambda screw the mixture beyond the cat's control?

Was the car properly warmed up, both water and oil needs to be up to temp. A good Italian tune up normally sorts it. then get it on the emissions tester before it cools down


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[Bigfootmgf]

Mine failed on emissions and it turned out as the sensor on the manifold apparently! I had high co2

[Charless]

You may be closer Paul, I had a look with pscan and found the 'oxygen sensor voltage' which should be constantly varying between about 0.2 and 0.8V is sitting rock steady on 0.45V. Even when I only look at the one sensor so that the sampling interval is the shortest possible. I could be wrong but would conclude a stuffed Lambda sensor and feel the garage would be best suited to change that! It may also be that the cat has passed away as well; but hopefully not - fingers crossed!

[NigelOBB]

You can sell your old cat it will pay for the new one


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[Rob Bell]

I think this is a Lambda fault.

You can use the pscan to collect telemetry for the Lambda. I did this on my Land Rover Freelander with the 1.8 K-series (MEMS3 - MEMS1.9 and MEMS2J will provide similar telemetry):



The blue trace is the pre-cat Lambda, the orange the post-cat Lambda. You should get a fluctuating signal as shown in the figure above. An old, failing Lambda will typically give only a signal when it is warm, often with a lower amplitude fluctuation of signal.

If the Lambda signal is appropriate, then this is likely a failed catalyst, but Lambda is easier* and cheaper to change.

[* when I say easier, that is not exactly to say it is easy, as you know they often become effectively "welded" into the boss!]

[Charless]

I know what you mean Rob. I judge it 'easy' enough to let the garage have a crack at it tomorrow amongst a couple of wheel bearings and some bushes!
Clean hands, empty wallet! Support your local small businesses!

I didn't try the pscan log but the trace was rock solid under all conditions so I am pretty certain that was the problem.
I think it is the first time I have used upgrade 042B which has MEMS 2J with 'Oxygen sensor voltage bank 1' and 'Oxygen sensor voltage bank 2'.
Bank 1 has a voltage readout but zeros for bank 2 - was this the first implementation of the KV6 or early pre MEMS3 two lambda systems? On my MEMS 1.9 cars 042B shows just one 'Oxygen sensor voltage' and displays the expected voltage oscillating - and would probably log like your blue trace above. I am sure this was the legend with previous versions of pscan on MEMS 2J but might be wrong.

[Rob Bell]

Good plan! Is it fixed?

Not used pscan for a MEMS2J yet: my MGFs are both MPi - so I don't know, but that [MEMS2J capacity to run a V6 or V8 with 2 separate banks of cylinders and therefore 2 Lambda sensors] is a possibility? ?

[talkingcars]

......... was this the first implementation of the KV6 or early pre MEMS3 two lambda systems? .......

I don't know about early ones but the ZS and ZT KV6 used Seimans 2000 ECU.

[Charless]

The Lambda had come apart leaving no flats on the probe to extract it from the manifold. The garage managed to get it out but destroyed the manifold thread in the process, so I provided them another manifold. It is now back to normal and the retest passed after a large bill which included replacing both rear wheel bearings and polybushing the back end. I will do the (easier) fronts myself sometime...

[Rob Bell]

The Lambda had come apart leaving no flats on the probe to extract it from the manifold. The garage managed to get it out but destroyed the manifold thread in the process, so I provided them another manifold. It is now back to normal and the retest passed after a large bill which included replacing both rear wheel bearings and polybushing the back end. I will do the (easier) fronts myself sometime...

Glad it's done now!