Technical Ducato Natural power missfire

[Kalle gas]

2019 ducato natural power missfire on both CNG and petrol. Have replaced: CNG injectors, sparkplugg, Ignition coils, .
This has made the missfire less prone, and give no fault codes on ODB-reader.
The symptom is simular to an old carburator engine run very lean, the car sort of hesitate and missfire when drive slow 50-80 km/h .
The symptom often disapear when on full trottel.

Can it be the cng pressure after regulator, or air flow meter?

any suggestion?

 

[Abarthmultijet]

If it missfires on both petrol and CNG it is likely not an CNG issue. Can you check compression on the cilinders? Have had a same problem (not on an fiat, but other car) and after a lot of trouble it was the head gasket leaking between 2 combustion chambers.

 

[Kalle gas]

If it missfires on both petrol and CNG it is likely not an CNG issue. Can you check compression on the cilinders? Have had a same problem (not on an fiat, but other car) and after a lot of trouble it was the head gasket leaking between 2 combustion chambers.

Thank you, i do a compression test!

 

[the green vanper]

Hello,

It's a known problem, the water gets into the engine bay, around the spark plugs / ignition coils.

There was a service recall some time ago, on the x250 (2007-2014). They said they resolved the problem, but they haven't, mine is outside the VIN range that has been recalled, but the problem is still there and the dealer offered to repair it if I pay for the repair...

The repair is quite easy though. To be done by every workshop or even on our own.

Attached the FIAT doc. It says the repair consist of cleaning the ignition coil housing and adding some silicone sealant around + new 'improved' seal.

What I've done and it resolved the issue for a longer period of time:

I took out the plastic engine cover. Disconnected the high voltage cables from the spark plugs. Dried around the spark plugs with a paper towel. With compressed air blown out the remaining dirt / humidity from around the spark plugs.

Disconnected the ECU for some time (I was checking it the terminals are not rusted and taking some photos, so max. 15 - 20 minutes).

And the problem was gone. It came back after another rainy autumn / winter

However FIAT says the problem is not water around the spark plugs, but around the ignition coils. So both need to be checked and insulated.

However the original culprit as with many other problems is the water ingress into the engine bay It has to be eliminated.