Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Sigma 1.6 issue, soft but continuous dropouts.

Today I had a 9.5 hour trip from South Bavaria to Cologne, about 760 km.
After one hour the car began to stutter it was no abrupt stuttering therefore I think it was no misfiring. It felt like lifting the accelerator but you keep it constant. It was clearest at constant throttle and moderate revs. A soft stutter. Twice at full throttle and 6000 rpm the power was completely gone.
It worried me on the highway because I was in the middle of trucks in heavy traffic but finally she brought us home.
But if you briefly touch the accelerator pedal during this failure there is full reaction again. That's why I don't think it's the fuel supply.

It could perhaps be the throttle valve motor according to my first guess. I still have a second TB and will exchange it and report if it helps.
Theoretically also the voltage supply of the TB by the ECU could come into question.
Has anyone experienced such a phenomenon with a Sigma 1.6 with wired TB?

Heinz not had this myself, if however briefly touching the accelerator solves the issue it could be the throttle - effectively a variable resistor like a volume knob on an old radio. Like an old radio knob that crackles, perhaps some contact cleaner may help? I fear its a sealed unit on the pedal but it may help.

I recall Cain had a throttle body failure - I think it resulted in a full stop/break-down. Not sure if he had the same issues as you before it broke down completely. A good call to swap the TB I feel to see if it changes.

One other thing - I did have a similar thing happen once that turned out to be a less than tight battery contact - unlikely but just a thought.

No but I had something very similar with the family Merc diesel - turned out to be a sensor on the exhaust

I had this on my +4 turned out to be water in the plug holes.

The spark plugs and their shafts are absolutely dry but I will unscrew the spark plugs tomorrow to see.

I replaced the TB, I know the spare one works fine, no difference. I drove in limp home mode by disconnecting the air mass meter, it could be guilty as well. (VCT doesn't work with limp home either). But no difference. The dropouts have a different character but they are clearly there, now more at full throttle.

After that I resetted the ECU, disconnected it from the battery and re-trained it. Now even power loss from 4000 rpm on in some situations.

It is not easy to isolate the error but the next try is the accelerator pedal. I think it is a bad candidate...or at least the plug or wire. If it's not the sinner, there might still be a cable break or ECU.

Heinz, is it a fly by wire throttle control, as opposed to traditional cable ?

If so the potentiometer at the pedal end is sometimes to blame

Jon, Yes it's a wireless gas pedal. I just wonder why it always drives well for about 30 minutes after a cold start. Can the wireless accelerator work well for a while before the fault occurs? Or can it also be the coil package? Because then I might understand better the delay. But I don‘t know if a faulty coil package can cause the symptoms described.

Heinz, suggest to try and find someone with a proper OBD reader in a laptop version that you can view live data on

You should be able to watch the resistance signal change as you rev the pedal, may have a 'notchy part' which shows up

Over here the breakdown services (AA & RAC) carry laptops that can do this, & I assume a Ford main agent could do it too

I ordered a cheap accelerator pedal to get my hands on it, 25€ on ebay from Riga just for a try. It is totally ok working. I proceeded exactly according to the part number. Because it turned out that Morgan also uses an RHD accelerator in the LHD car. So I ordered this pedal. On the photo you can see that it is sawn off at Morgan and two holes have to be drilled for the rolling pedal.

I wouldn't have thought the positive result possible. Especially because the error always appeared after a while. Not only that the error has disappeared. My old accelerator pedal must have been bad for quite some time. It's almost as if I didn't change the accelerator but the engine. How soft and silky it runs now. The response of the pedal is better in classes, much more sensitive. And at half throttle in fifth gear the rpm climbs steadily. Before I had to help and always push the throttle to get faster.

I didn't learn it anything, it worked just like that. I also opened the old pedal. There are fixed resistance values soldered on. These values should be quite standardized.

So I learned something new again. On the left is the new one.
Thanks to all for your helpful suggestions.

Brilliant that you have found the culprit Heinz - good info for the future as well. thankyou