Z4 E85 2.0i Misfire

[Barnie]

Hi Folks,
Newbie to the forum, so thanks for the join.
I own a 2007 2.0ltr E85 Z4 which I have been slowly restoring for the last couple of years, earlier this year I replaced all the plugs and ignition coils as I had a coil that failed, I couldn't find a list of them ever being replaced in the service tickets, so bite the bullet and just swapped the all out. I've now recently developed another misfire issue which I'm trying to identify its source and could certainly use some input in trying to identify it, my local garage hooked it up to the computer to see if there was any identifiable error codes that came up, it came up with no error codes but registered a misfire on cylinder #2, so I swapped over the coils between cylinder #2 & #3, to see if the misfire jumped cylinder to denote a failed coil, when connected back on to the computer it is now showing a misfire across all cylinders... lol
So the question is am I now looking at a potential failure of the variable valve timing (VVT) solenoid? Or does anyone have another possible reason for the failure.

Thanks in advance for any feedback.
Barnie

 

[Special Kay]

Hey Barnie, welcome to the forum. Something similar happened to me on my daily, the car was driving awful and at times borderline dangerous. At the time I replaced with all new cheapish spark plugs and the flagged cheapish ignition coil, this didn't solve the problem for me either. I kept getting a flashing eml showing no error codes, intermittent misfires which gradually got worse. I was trying to wait for a definitive eml and an error code which never seemed to stay on. I then just decided to replace with all new oe quality coils along with all new spark plugs. This immediately felt better, and has remained so.
I wish I could give you a more definitive answer, I think I just got lucky. I hope someone more experienced comes along and provides you with some guidance. Good luck

 

[Barnie]

Quick update, having done some further research into this, it would appear the issue could possibly be with the VANOS timing solenoids that are a part of the VVT control, two solenoids fitted, one does inlet and the other exhaust valve operation, it would appear they are prone to a dirt build up, and or general failure, which then throws out the timing, leading to misfires and a general power loss, mimicking a coil and plug failure.
According to the mechanic I spoke too I can take them out relatively easy and clean them up with a can of standard brake disc cleaning spray solution, or just replace them. I've found new ones on Ebay for between £30 & £60 for the pair, so currently thinking I might as well just order replacements if I'm going to have to take them out to try and clean them anyway. Hopefully get round to it next week and will let you know if it curse the issue.

 

[Special Kay]

Quick update, having done some further research into this, it would appear the issue could possibly be with the VANOS timing solenoids that are a part of the VVT control, two solenoids fitted, one does inlet and the other exhaust valve operation, it would appear they are prone to a dirt build up, and or general failure, which then throws out the timing, leading to misfires and a general power loss, mimicking a coil and plug failure.
According to the mechanic I spoke too I can take them out relatively easy and clean them up with a can of standard brake disc cleaning spray solution, or just replace them. I've found new ones on Ebay for between £30 & £60 for the pair, so currently thinking I might as well just order replacements if I'm going to have to take them out to try and clean them anyway. Hopefully get round to it next week and will let you know if it curse the issue.

Ah that's a great reminder, I cleaned mine in the summer with brake cleaner, in a desparate attempt to remedy my misfire, prior to fitting new plugs and coils. They didn't appear to be particularly dirty when I took the solenoids out. So a good clean and I reinstalled them, but it didn't help my issue out at the time, not until I replaced the plugs and coils. Good luck, I hope this along with the other replaced parts remedies your issue.