I'm hoping someone here can point me in the right direction as I have been struggling for about 2 years now. I'll try and keep it brief.

I have a Dimma Williams, bought it a few years ago drove okay, wasn't great but drove well enough. Parked it away for a year or so (garaged) and then when I went back to start her she wouldn't idle, misfiring etc. Took it to a local Renault dealership. It sat there for about 5 months, they replaced a bunch of parts but went on about some sensor they couldn't get. Gave me a bill and returned it in the same shape but overfilled with oil.

I found a better rated dealership where they seemed to know about the williams, sent it off there. Similar story, sat for a couple of months. Apparently the ECU was corroded, they tried various things to duplicate the software and put it on another ECU, apparently it would not work and now they could not put the software back onto my original ECU because it has a 'prima power' chip. So another bill and now I have a non runner. The only difference was they tested all sensors and the health of the engine which gave positive results.

Are these cars really that hard to sort out with ECU issues or am I just being shafted non-stop? Can anyone assist or point me in the right direction.