Talk Morgan Forums Morgan Sports Cars Morgan Aero 8, 2012< Plus 8, SuperSports, Coupe & Aeromax Engine management light...

That's interesting! I have a sports exhaust fitted but the light can stay off for a period of time! Then suddenly, it would just come on and stay on until it's reset.

If what you say (about the CAT) is the cause of the light coming on, why doesn't it happen immediately instead of after a period of time [after it has been reset], and after the car has been on several runs?

I think that it could be just an over-sensitive sensor which needs replacing.

That is because the cat is functioning most of the time but if you look at the readings you will probably see it is right on the limit. Mine usually seems to come on after a spirited run when slowing down with no throttle. In this situation little or no petrol is being injected and the engine is working only as a pump to pump "cold" air through to the cat. This would cool the cat below operating temperature and as soon as throttle is reapplied the cat would show a malfunction. Other circumstances may create the same problem. The pre-cat sonda lambda can also be replaced with a faster sensor but I have reliably been informed that this does not seem to make much difference.

The ECU is programed to ignore the apparent malfunction for a certain period after the car has been started to allow the cat to reach operating temperature.

If you need to take the car for an emissions test as part of the registration renewal process make sure the car is good and hot before they run the test, particularly if you have a sports exhaust system fitted. Many sports exhaust systems have a 200 cell cat fitted which may be high flow but marginal in catalytic function. Now many sports systems are being fitted with 400 cell cats which function better. Mine has been changed to a 400 cell cat but it has not entirely resolved the problem.

Changing the sensors may help but it is probable that the system is right on the borderline in any case.

When I took delivery of the Max, it came with standard factory-fitted exhaust pipes which I ran with for almost a year before switching to the sports exhaust. In either case, nothing has changed: the engine management light still came on and stayed on for both [exhaust] systems!

And owners replying on this tread also experienced exactly the same problems as me! Their solution? Replace the troublesome sensor which is what I intend to do after the festive season.

If it was the change in exhaust systems that's causing problems, why would the light behave as it does before the upgrade to the sports pipes?

You may well be correct but don't be too surprised if it continues to happen. Unless the standard system is completely BMW, which I doubt, it is probably more sporty than the original BMW system.

The primary exhaust headers on the Aero's are stock BMW (which is why they are not great in terms of performance - see extensive discussions on here about 5 years ago Re. header design and optimisation). The lead motorsport engineer at Richard Thorne's - now at Mulfab designed a performance optimised set which are very elegant and make quite a difference.

Anyhow - back to the point.

The situation of the Lamda Sensor on Aero's physically is not ideal and, as you are finding, can lead to premature sensor failure.

Easiest to get and OBD2 reader and you can check the code yourself and clear it. I have also had one instance of cat failure and exhaust blockage which gave the opportunity to test a theory about De-catting.

I knocked the core out of the cat to see how the ECU would react to various stimuli. Suffice to say, easiest to fit a sports cat than poke around with the electrics.

Cereal, I don't know if you would agree with this but I have been told that even if the headers are standard this problem can occur with a more open cat and silencer system. The theory is that with less restriction the gasses flow more freely and, under certain circumstances the temperature of the cat may drop too low for it to "light off".

What do you think?

If you can find a link to that thread I would be very interested to read it.

Just for the record my plus 8 has the factory sports exhaust fitted and when the light was coming on, in my opinion, it was linked to short journeys.
While I was waiting for the replacement sensors to be fitted I did approx. 400 miles with the light on and whilst on a swift drive on a hot day, the light actually went out and didn't come back on before the new sensors where fitted.

This is the OBDII reader I use:


OBD Thing

This is the iPhone App that "talks" to it:

App

Yes, it is free but only as a reader. To re-set you need to pay for the upgrade, about £10.00.

Android Apps also available, about £25.00 the lot.

Thanks Peter. I will talk to Brands Hatch Morgan where my car is serviced to get the sensors checked/replaced after which I may end up buying a reader.

I've got one that looks just like that. It won't talk to the iPad but it works fine with Android. The app I use is Torque. The free version allows you to re-set the error code but the Pro version which has a very small charge is much better
http://torque-bhp.com/