CEL - misfire

You may have an issue with the ion module. That is the guy that actually controls the spark and knock control. I have had to replace them not only in the Ferrari cars..but now Lambo is starting to show some failures.

 

You have done the basics..I suppose you could go ahead and swap injectors from bank to bank and see if the problem follows but that is a ridiculous amount of work and you could introduce injector sealing issues etc. These newer turbo DFI cars (not just Ferrari) are really starting to show some stubborn issues.. good luck with it.

 

One other thing you could try. You could oscilloscope (peco scope is the standard tool we use) to monitor the charge and release of the ignition coils on those cylinders. You can watch what happens on the primary side of the coil (control) and compare what you see against the cylinders that are not misfiring. That is how we found the issue on a 488 earlier this year.

 

Really common to have dirty injectors and heavy carbon on the intake valves at these miles. Depending on how dirty the injectors can cause misses cold due to very poor spray pattern or moderate and heavy load miss fires due to low fuel flow. We regularly clean both the injectors and the intake valves around this mileage.
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IMO if the issue is fuel, FI cleaners like techron can clean injectors but not very well. cleaners IMO are like a hail Mary. It is kinda like rinsing your mouth but not brushing your teeth. There is still a bunch of junk in there. I guess it's expensive if not DIY but I pay about $30 per to get them professionally cleaned and flow matched. For me it is cheap and I do that at every major service as well as walnut shell the intake that is super fast and easy to do when the cams are out of the car. It is a lot easier to prevent these things than try and figure them out. But so far you have only picked the lowest hanging fruit. Your mechanic is right. Next stop clean injectors.

 

Wow, now that's an ugly intake tract! Reminiscent of the old BWMs where walnut blasting was the norm for rough idles and misfires. How little times have changed, even with advance EFI technologies.

 

No not at all this is routine maint. The valves no longer get washed by the fuel from indirect injection. PCV gasses build up in the intakes and on the intake valves.
Carbon builds up on the injectors. Pretty standard on all direct injection engines to remove the intakes and clean intake valves with walnut chips and then clean, flow test the injectors and replace the baskets and teflon seals.