Idle misfire on rs250

And when you are moving, does the misfire still occur

 

So everyone could be forgiven for jumping to the conclusion that it's the O2 sensor.

 

Had the car been mapped?

 

So you know what's coming now .. must be the remap

 

Which o2 sensor did you replace? As theres two?

 

Wow that's good to know
you wouldn't think that would be related to your problem, vey helpful

 

I have had an odd misfire but when on power (boost) it has been okay for the first few laps on track, then gradually would get worse.

It got really bad on the way to Thruxton months back, got a replacement ECU and that seemed to have sorted it, but it came back at the ring two weeks ago, but was fine driving it home.

Well yesterday i was at LeMans and it happened again, started misfiring and in the end i lost cylinders 2 and 3, replaced the coils with some spares i had, then it was better but still not 100%, so i fitted a new set of spark plugs, exactly the same.

So replaced the crank sensor, no different.

Pulled out the glove box, removed the BCM (as the Icarsoft says it has a Canbus fault) wiggled the wires, gave it a few smacks and still no better.

A friend i went with said try my pencil coils, pulled all four of his out of his red hot engine, fitted them and it was back to 100%, swapped out 2 & 3 coils, still good, changed number 4 to one of mine still good, pulled cylinder 1 and fitted another and the misfire was back, swapped out with another and all was good.

The rest of the day went without any engine problems.

So with two sets of coils, i had a duff coil in each set.

And my OBD test said and showed no misfires on any cylinder.

 

Are you running aftermarket pencil coils @ianplymouth

my mate had issues with aftermarket valeo green tops doing exactly the same on track. Changed back to oem/beru and no issues since. I recently had the odd misfire on green tops, which went after fitting new beru.

 

The ones that were fitted were Beru and i'm sure the ones i have as spares were also Beru as they have a light to mid grey tops

 

As far as i know the grey tops are aftermarket bosch or similar, beru/oem are black with no cap on. Ive not used the grey top ones, but can remember Chris @ efi saying the green top ones are terrible.

 

I have completely the same problem. But I can’t understand. How that valve can affect at idle?

 

thanks. I also have that parts new but it not helps (

 

yes I have st3 map. And also I have new dmf with new clutch. Done half a year ago