Misfire when cold
 

Looking for ideas. I have a recurring cylinder specific misfire code P0303, but it really only occurs when cold. I've swapped coils and changed the plug, plus I've searched for intake leaks and nothing has eliminated it yet.

40,000 km
Innovate supercharged with IC
Cusco oil cooler
Dual radium catch cans
2-3k on upgrades before first CEL, oil cooler only 100km prior

Prior to taking it in to the dealer I'd like to eliminate the likely causes. I find it odd that it only occurs, or at least persistently occurs when cold. When its cold I can almost notice the misfire like hesitation when it occurs but once warm it's perfect.

Also the CEL doesn't stay on, only blinks. It doesn't seem to pull any timing, just happens and goes away. Idles and starts great, and no odd noises.

I feel the characteristics eliminate many possibilities. Cylinder pressure, port and direct injector seals, general intake leak, plus I eliminated coil and spark.

Any thought?

Do you have access to logging engine parameters ?

if so run log from startup logging normal stuff afr timing fuel trims and cylinder misfire counts ect might turn something up oor at leat isolate problem to a cylinder.

unfortunatly at startup and warmup heaps of offsets are applied untill coolant temp gets up and for cat warmup unless they have bn disabld in your tune so interpreting these logs can be difficult but misfire count per cylinder would be usefull, could be as simple as spark plugs

Maybe check the tune ..... :iono:


humfrz

Thank you for the suggestion. I didn't even notice I could log misfire count by cylinder. Logged this mornings drive, got 2 misfires one in #2 and the other in #3. No CEL. Both registered while warming up.

The #2 is interesting because I've only ever had P0303 which is specific to #3.

If it persists across multiple cylinders it may be a vacuum leak after all.

Will log more today...

It's worth a try, once I've logged the current map ill try out another.

Thanks

Any update on this? I'm having the same issue.

What are "normal" misfire counts in a healthy engine/tune? Should I see 0 misfires all the time?