Never been really happy with the way mine runs, this misfire of yours what were the symptoms?

 

The first sign of the misfire was when the car was under Load. Very minor and to the point that it felt like it may be a spark plug or coil breaking down. No loss of power.

I had the car serviced and new spark plugs fitted. The next day the car ran like a bag of spanner’s and wouldn’t idle without stalling but if you let it warm up and stopped and restarted it, the car would be fine. But the next day the same would happen.

 

Interesting that the Flush made it worse because that indicates where the problem is. The TwinAir is critical on oil to operate the valve opening so probably had the wrong type fitted. Now you are chasing stuff out of the system

 

From the Fiat 500 Forum...

How MultiAir works

When the electronic solenoid valve is closed, the chamber becomes a solid body and the valve follows the profile of the cam exactly.

But if the electronic solenoid is opened to release some of the oil, the chamber shrinks to absorb the cam movement and the valve opens less.

Choosing when to bleed the oil from the chamber, as well as by how much, makes it possible to control timing and lift as well as the duration of opening on an individual, valve-by-valve basis.

The mechanical inlet cam profile is 'hot', that is to say designed for high power at high rpm.
For maximum power, the chambers remain full so the valves are opened to their maximum for longer.

At slow speed, the solenoid is opened near the end of the cam's 'ramp' to close the valve early, maximising the amount of air trapped in the cylinder and improving torque.

At part throttle, different strategies are used, partially opening the valves to trap just the right amount of air and speed up air flow.


The oil/fluid link is actually engine oil, so if it's really low on oil or can't pump it around it can't work properly.

There's a oil screen screwed into the system under a blanking plug in the middle of the cam cover, I did a post regarding cleaning out the screen a while ago.

 

And read this about Lambda Sensor being the fault...

Technical: 900cc Twinair rough start from cold - The FIAT Forum

 

Interesting that this post mentions using 5W 40 as AlfaShop told me that was the incorrect oil for mine and advised to use 0w 30?

 

After reading through that thread, mine doesn't seem all that bad by comparison. I am going to move the oil change (using correct oil this time) higher up the to-do list though.

 

And this one suggests the oil filter is to blame. The guy put the old one back and the oil warning light was fixed.

Technical: Twinair Oil Pressure - The FIAT Forum

 

Thanks for the info Old Engineer.
The garage has now removed and refitted the MU and primed the MU for longer. The car now runs fine and hasn't missed a beat since. There is however a slight, very quiet tappet noise. Not sure if this is common after a MU change?

 

If only I had just a "very quiet tappet noise" re the oil though, mine had 5w40 fully synthetic put in it last time. Upon querying it was told it was within parameters for the twin-air. Going by the Mitoregister useful info and Alfaworkshops site, I'm opting for the 0w30 Selenia this time.

 

The earlier TwinAir's had 5w40, with later cars running on 0w30 - you need to check the service manual for your particular car - not sure if there's a material difference in the engines across different years so it might be possible to run the TwinAir's on either of the oil specs, but definitely worth checking as the TwinAir's and MultiAir's are otherwise not tolerant when it comes to oil viscosity, quality and level.

 

EU5 engines are 5W-40 C3, later EU6 are 0W-30 C2, as far as I'm aware no material differences that have been found between the 2 engines, at least where oil should be a factor.

As mentioned, check your handbook for the correct type, it'll reference fiat specs for either, which a lot of oils will meet, look for Petronas, it's Selena's parent company and will likely be easier and cheaper than sourcing Selenia.

It's recommended on the fiat forums that oil be changed at 9k mile intervals, there is no service interval I've found which mentioned cleaning out the bolt-type filter, but it can't hurt.

Obviously oil pressure on these engines is critical given how they operate - the oil filter itself has a peg which fits into a hole in the filter housing, and it's very easy for it to be fitted incorrectly and not seal properly.

 

I beleive that mine has the later engine (2014 105bhp) but I will be checking before purchasing any bits. Probably only done nearer 4k of commuting mileage since last oil change. As for doing the work, it will be my local Alfa Indy. My TS spider has for the four years I've had it, been run on Selenia 20k. In that time I've used 2l in topping up. I'm quite happy with the brand however will now cross check for any pricing differences as the Mito oil is looking considerably dearer.

 

I took the plunge and bought the correct Selenia oil with a genuine filter, had work carried out at local indy (with service resets etc). I don't know if it actually runs any different but for my peace of mind, it was worth doing.