029F Cylinder misfire #3 E81

[Stebee]

Hi all. New account as i cant get into my old one. Got the lads 1 series 2008 E81 2L with 116k on it.
Drives fine then will drop to a very rough idle, orange outline EML comes on and the foxwell says 029F cylinder misfire #3.
Clear the code and the engine idles ok again.
I have moved injector and coil pack 3 to cylinder 1. No effect.
New spark plug in cylinder 3.
If i pull the injector connector while running it drops to a rougher idle and doesnt bring the orange outline EML on like before but brings the EML symbol on the square display above the mileage. Plug it back in and it runs fine again.
Ive wiggled the wires from the injector all the way back to the white box on the passenger side scuttle. The wires do go into some sort of splitter type box by cyls 1 and 4 but Ive not opened those.
If it was a valve or compression it wouldn't be so random and i'm fairly sure it would do it all the time. Or all the time cold or all the time hot. Sometimes it will go a week or so then do it 4 drives on the trot. Completely random.
Ive looked at the smooth running values and while 1,2 & 4 are hovering around 90-110, cyl 3 is -200, -300 area. I guess this is a measurement of force measured by the crankshaft sensor so what could be causing this problem?
I dont want to get the parts catapult out. The car is only worth 8 quid but to him its a million.

Thanks to all who assist

****Correction to title 29CF is the code.****

Steve

[MarcoZandrini]

Hmmm, the EML light signifies that something isn’t right with the electronic motor load regulation subsystem (EML in BMWspeak). Are you sure you’re not seeing the Service Engine Soon (SES) light? What is the code that the Foxwell is giving you?

[Stebee]

EML Engine Management Light. Code for the misfire is 29CF. "electronic motor load regulation subsystem" is for electronic motors and I really dont know what you are referring to when it comes to a BMW car engine.

[MarcoZandrini]

I think what the code is referring to is the electronic throttle body. Your car has throttle by wire. That is, it doesn’t have a throttle cable. BMW started using throttle by wire in the late 1990s. Instead, the accelerator pedal has 2 matched variable resistors. The resistance of these resistors changes as the pedal’s position changes. The engine computer (DME in BMWspeak) constantly “reads” these resistors and opens or closes the throttle body according to readings and several other factors. It sounds like the throttle body needs attention.

[Stebee]

Hi. What?

So why is it only cylinder #3? The throttle body would affect all cylinders. The whole engine would run rough if the throttle body was at fault. The lambda sensors would be all over the shop if the throttle body (TB in BMWspeak) was was reporting duff info.

Thanks for the lesson in fly by wire.

[MarcoZandrini]

Yeah, you’re right! Just odd that the EML light is on. Check the electrical connector for the cylinder 3 coil. Make sure the pins and sockets are clean with no corrosion or burned spots. Next I’d check the wiring from the connector to the DME.

I concur that the misfire likely isn’t caused by anything mechanical but either and electrical or a faulty injector. It’s odd that cylinder 3’s compression is significantly higher than the other cylinders. I don’t know if that’s good or bad.