Hi struggling with this one which came in a month ago for a service with a slightly rough engine which now has developed into a misfire. The misfire is at low revs up to about 3000rpm when it disappears (not always)(more of a weak misfire than losing a complete cylinder). There are no codes I have checked with a noid light for feeds which flashes for about 5 cycles & cuts out. I think these being piezo injectors, I’m not sure they are supposed to be disconnected while engine idling in case of over fuelling & hydraulic-lock? But the noid appears strong on all injectors.

I have bought one new genuine Ford injector & swopped with all cylinders but only found a slight improvement on No. 3 Cly. All the compressions are good; all around 300psi. The fuel pressure at idle is 300 Bar rising to around 1100 Bar when revved. Before disturbing the injectors I carried out a leak off test & all injectors were spot on with each other. I assumed the new injector required calibrating but IDS said that unless the injector was different to categories 4, 5, or 6 do not calibrate. I’m left wondering if the ECM is not driving the injectors correctly causing the misfire. I have also checked with the customer if he has ever put petrol in the tank by mistake as this is a one owner car but he says not; the vehicle has done 80,000 miles. The only other point I was wondering about was Pico scoping the injectors, this is not my strong point especially as these appear to be piezo injectors & not sure what to look for (yet more training needed).
Any help on this one would be most appreciated.
John Kennard.