Why would clearing a fault through Bimmerlink make the problem disappear

[Gepetto]

I have a 16 year old BMW which I love, but the engine (N53) has a known issue with the injectors at around 80K miles. As it's turned cooler I've developed a rough idle, about 20 to 30 seconds after start up, that goes away as soon as the engine warms up.

The other morning this was a bit rougher than I would have expected, and the engine warning light popped up. I expected this to go away as soon as the car warmed up but it didn't.

My son, who was looking up the fault code at the time, told me it was a misfire on Injector 6 and cleared the code.

The instant he cleared the code the rough idle vanished! What? I would have expected the EML to disappear as soon as the injector had warmed up, not the other way around.

It seems to me that BMW software perpetuates the fault even though the problem is simply not there anymore. Anyone else had experience of this?

 

[Gepetto]

When the ECU noticed an issue with injector 6 it probably disabled it or put it into a very safe state of operation to stop it potentially causing damage, so now it's been reset it'll start to use it again as normal until the fault threshold is met again.

So unless it was just a spurious reading from some of the sensors It probably won't have magically fixed itself.

Thanks, the problems with the N53 injectors is apparently that they leak, therefore the rough idle is caused by burning off the fuel sitting in the top of the cylinder (never a good thing).

I'm not sure that what's happening here due to the engine running smoothly for 20-30 seconds then developing a rough idle.

Perhaps a sensor is at fault. I'll investigate that. Cheers.