Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Some clues welcome

Good morning all,

Since owning my Series 3 Roadster I have experienced intermittent P0133 MIL situations which some say can be quite common on these engines. `I usually just turn the MIL off . I changed the sensors upstream when it first happened at 8000 miles and now, at 20000 miles it is happening again. I took them out and left them in petrol to clean them as they were very black. It is always the right hand side upstream sensor which triggers the slow response signal. Some times the engine will run fast for a while, particularly when cold and some times it will do so even when hot. A couple of days ago I thought that I would experiment with a right angled extender and in the course of so doing drove 160 milles of mixed motorway and urban roads. The car performed faultlessly: no mil, no rev hang, smooth running and 34 mpg. Is it then obvious that the sensor is at fault or is that a red herring and I should look elsewhere ? I wouldn't have thought that the MAF sensor needed cleaning but I could be wrong and I cannot sense any leaks. Two days ago the car went for its control technique and passed with no advisories.

On my S1 Roadster I got something similar especially in winter on the passenger side. I found using non supermarket fuel cured it

I don't know about others on here but I consider supermarket fuel to be for emergency use only, I wouldn't even put it my lawn mower !

I always put BP Super Plus in the Plus 8 and it helps.
Not too fussed with the tin tops if I'm honest.

I hope it's a simple fix such as this Ian.

If I do use it in the Mog it is the super version. There isn't much choice around here. The nearest is Esso & the Shell garage involves a 10 mile drive.

I had this problem with the S2 Roadster and still have it with the Aero Plus 8.
Always the N/S downstream lambda sensor slow to respond.

After talking to may people and trying different fuels I started keeping a diary, noting when it happened the weather, driving conditions and style. I've done this for over 30,000 miles.

Conclusions: it happens when the cat gets cold and isn't working optimally. This seems to be caused by the weather and by how you drive: if I keep the revs above 30% and vary the throttle opening frequently it doesn't happen, so enjoying the car on a B road it is fine.
If I have been pootling along in top at 50mph in traffic on an A road, then suddenly change down and accelerate hard to overtake it will most probably happen and if it is below 10C then it will certainly happen

Choice of fuel doesn't seem to make much, if any, difference.

Short of insulating the cats and exhausts and fitting spacers to the cats I don't see a solution.
It is easier to clear the light when it happens.

Bottom line: "they all do that sir"

More seriously, it isn't a fault, it is an observation and it is caused by putting a large and powerful engine in a small light car, so it isn't working very hard. So drive it like you stole it and all will be well...

I have heard this said before anecdotally but why scientifically?

Honest John, the Daily Telegraph motoring correspondant, has a lot of information on fuel quality on his website. He much prefers Shell V-Power and has research to back this up.

I use Shell V Power most of the time........and I've never (so far) had a light on my Roadster.

If I have been pootling along in top at 50mph in traffic on an A road, then suddenly change down and accelerate hard to overtake it will most probably happen and if it is below 10C then it will certainly happen
Yes that does happen.
I am careful about fuel and only use my preferred ( i.e. they are always nice to me) petrol station.

So is the consensus that I shouldn't look elsewhere ? And what about the fact that I used an extender and everything was better ? Am I storing up trouble?
Thanks for all the replies.