Purchased a 2015 Fiat 500 Pop (111k miles) over the weekend. According to the previous owner it had oil changes religiously. Supposedly they drove to work, car was okay, came out after shift ended, started and rough idle. Took it to a mechanic and he says cylinder 4 has no compression. Knowing the MultiAir is not your conventional engine I'm guessing the diagnosis is not the complete story. I haven't pulled any codes yet but will post those soon. Looking for advice on things to checkout.
You are probably more familiar with it than me, I am just an old school mechanic.
From the little I have seen it appears the hydraulic valve control that is electronically operated can be susceptible to dirty oil or blockages preventing the valves from opening, though why it should be just one cylinder I don't know.
I suppose given the complexity of the system it would guide you to a fault in this direction, there is a utube video about bleeding the system but given the guy you bought it from was using it regularly it doesn't seem likely, as that one was where it had been standing and the oil drained away.
Me being old school, I would be tempted to give it an engine "leak test" which would at least prove if it is an inlet or exhaust valve operation failure or something else like a piston or head gasket etc. that is giving low compression on No.4.
Presumably even technologically advanced systems can still get burnt out or sticking valves.
From there I would take the cam cover off, check physically what the valves are doing when cranking, hopefully that will guide you re the hydraulic control side.
Just a thought, any chance of a faulty electrical connection to the hydraulic control for that cylinder.
I trust the purchase price was right
. It seems to me that manufacturers are deliberately make cars so expensive to repair that we will be grateful to buy their electric offerings.
When I did my apprenticeship in mechanics we could usually fix most broken down cars at the side of the road.
