Evening

After about 5 minutes driving this morning my 57 Focus this morning the red light next to the milage dispay started flashing and the car went into speed limit mode. I turned the engine off and tried again, another 3 minutes and it did the same.

I got taken to a garage where the diagnostic tool told them there hadn't actually been a fault. They changed the spark plugs as a precutionary as they would have been due in 5,000 miles and one was well past its best. They also told me to fill up with Shell or BP fuel not supermarket.

The car has been working fine for the rest of the day at various speeds.

Any ideas what could be wrong? Could it have been the spark plugs or the type of fuel?

Thanks in advance.

I'd have thought anything serious enough to bring a red engine light on and put the car into limp mode would leave a couple of DTC's as a calling card?

Unless the faults are deeper into the ECU than the generic ODB2 dtc's and need something with ford IDS capability or equivalent to read them.

You'll have been unlucky if it was fuel related, though putting a tank of Shell or BP in would soon give an indication if that's true or not. If it was plugs you'd maybe get misfire dtc's but again I can't say if these would come out via OBD2.

Last thing, the plugs should all look pretty much the same - in what way did one of them look past it's best and not the others?

In truth ive used supermarket fuel and some cars dont like it it is possible the rubbish fuel was the issue if theres no more issues then you know its probably been that