Cylinder #3 not firing. Any thoughts?

[anthonymax007]

Hi guys,

I was having some trouble with my spark plugs. Two of them were drowning in oil. I replaced the valve cover gaskets and bought new spark plugs. I also noticed that the 3rd ignition coil was blown (literally, the side of it had some white stuff coming out of it) so I ordered another one of those. Got everything put back together and the 3rd cylinder is still not sparking. The wires are good, the faulty coil has been replaced, and I have no idea what could be happening. Any thoughts? I did the stomp test and got the Lambda 2 code (1222). However, the check engine light is not coming on. I'm hoping that oil didn't work its way down when the spark plugs were flooded. Right now thats the only thing I can think of that might have happened.

[roguetoaster]

Well, as you know, it could be the plug wire, the coil (new one defective, doubtful), the wiring to the coil from the driver, or the coil driver.

I suggest you start by swapping an known good coil over to 3 and the new one to another position. Do the same with one of the plug wires. Be sure to label your wiring going to the coils. If it's not either of those I would guess it's the coil driver, in which case it's new (used) ECU time.

[anthonymax007]

Hmmmm. I've already switched out the spark plug wires, and they all tested fine. I'll try switching out the coils when I get home. Thanks for the suggestion, not sure why I didn't think of that last night.

How can I test to see if its the wiring to the coil from the driver, or the driver itself? I'm not looking at my engine bay right now, but I thought all the wires ended up being routed together. Is there a way to easily replace the wires?

[roguetoaster]

I doubt there is an easy way to replace the wires to the coils, but I also doubt they are damaged/bad. Check M42Club for info on coil drivers, should find all you need.

[anthonymax007]

Thanks for the help. Tested the wires from the coil to the ECU, they're all fine. Opened up the ECU and some of the components look like they got wet, but most of it seems to be working fine. I'm testing the pin for the ignition coil, the hard part is narrowing down the circuit that it operates, but there is a portion thats not giving us a signal. I'm checking the classifieds for an ECU. I think troubleshooting all the circuits is more trouble than its worth.

Thanks again!

[anthonymax007]

Got it sorted. Pulled the ECU part and found the damaged transistor, BOSCH 30004, which was most likely damaged when the coil blew. Found a new ECU and she's purring like butter. Well, as much like butter as a 1.8L four cylinder can. Thanks again for the help.

[roguetoaster]

Glad you got it sorted. Be sure to hoard all working M42 ECUs in future as this is bound to become a more common issue as original coils get to be well over 20 year/many, many thousands of cycles old.