Hello All,

Sorry for my first post being a problem, but I've been searching for weeks and I've often ended up on passion ford via google with similar, but not identical problems and have been impressed with the users knowledge.

My girlfriend has the 1.3 Duratec (2003+) Ford KA that has a strange missing / hesitation problem.

This problem only occurs when the engine has warmed up (so is running closed loop I think), only at low rpm (I'd say under 3000rpm, but no RPM gauge to see for sure) and feels like the engine is missing once or twice as it accelerates under load.

So far I have tried changing:
Front Lambda (o2 / HEGO)
Plugs
Leads
Coilpack
Oil / filter
fuel filter
Air filter

I have also tried:
Cleaning TPS / TB
Cleaning all engine earths
Unplugged rear lambda sensor and went for a drive, still did it so plugged it back in

As it's ONLY at low rpm and ONLY when the engine is warm I have to assume the ECU is using sensors that are only used at that part of the engine map, but I don't know what. I thought it would be a lambda sensor for sure, but it wasn't.

I'm starting to lose the plot on this one, engine experts please provide a hint! I couldn't tell you if the engine is missing or pinking, there's a definite loss of power like a miss fire and a slight popping sound from the exhaust.

Thanks in advanced.