any ideas why marea 1.6sx (w2000) should run intermittently ok then very rough. it is at fiat as we speak but they have run out of ideas after replacing fuel potentiometer that showed faulty on diagnostics. however still not running properly so checked jets, timing, fuel pressure etc. if i remember properly they said air is popping through inlet manifold under hard acceleration but cant find out why. sorry this is a bit vague but would be grateful of some pointers as to intelligent questions to ask before i shell out £500 quid for car that sounds like same problem as what went in with
cheers

Hi horse and welcome to our forum
Sorry to hear about your problems.

All I can think of from your description is a problem either with your inlet manifold gasket (which they should have picked up straight away) or a cracked/porous manifold which would have to be removed first to check. Not a very common fault though.

Another possibility could be a damaged fuel or brake servo vacuum pipe or a problem with the fuel vapour purge system.

Good luck,

thanks for the pointers- i will mention them to the fiat dealer. at the moment they are contemplating getting specialist from fiat uk because they've run out of ideas.cheers again and will let you know what they say.

fiat have discounted these possibilities and have now decided that its most likely the ecu - but say their diagnostics cannot test the ecu itself. is this correct ? they have come to this conclusion after swapping ecu from another marea which cured problem by 90%, say may not be perfect due to not being the exact ecu for my particular marea. dont seem to want to guarantee changing ecu will sort problem 100%. grateful for anyones comments on this coz im thinking its about time to get tough . cheers

If they change the ECU they need to put the correct one back in otherwise you will have loads more problems. They are unlikely to order in a new one just for a test.

Its a very expensive gamble, I would try to find a compatible ECU to test with first.