On my way home the other day my car started shaking pretty bad SES light came on and a reduce engine load message came up on the idrive. Ever since its being running pretty bad and has no power. I read the error code and got a p0304, p0306 which are missfire codes and a p1412 that I've searched everywhere and no real info on this.

I have an 04 525i with 90000 miles and I've just had it serviced with new plugs coils and o2 sensor.

Any help will be appreciated.

 

P1412 is the secondary air pump, i.e. emissions air pump. check for a loose connection around the pump. you might have to remove the right headlight to access it IIRC.

 

Right as in the passenger side??

 

A secondary airpump shouldn't cause any issues like this though. It's just to get the cat ready..an emissions related item.
I would think you have a vacuum leak somewhere up top where the air intake comes in. Could be several different things. Your misfire codes are what's causing your issue not the secondary air pump. You can unplug it and drive just fine.

Welcome to the forum.

 

Do you think an emissions smoke test will reveal that?

And thanks for the welcome.

 

reveal what? a vacuum leak? sure, but perhaps you didn't seat your plugs or coils correctly or close your oil cap all the way.

 

Yeah reveal a vacuum leak. I've even replaced the plugs again (ngk platinum) since it started. And I made sure the plugs were in tight. I've even swapped the coils around and still the same codes. Ill go for a smoke test tomorrow since I'm out of options.

 

Why don't you pick up some coils and try them out. if they don't work out for you, return them.

 

I just recently changed the coils along with the spark plugs. I got a smoke test done but no leaks so Idk... dealer it is I guess.

 

yes, that's where it's located on the car. that's what that P-code references, but that is not causing your running problem. that air pump will not affect the running of the car at all. you can remove it completely, and other than triggering a fault code you're not going to notice any difference on a properly running car. i even think there are emulators out there that let you remove it.

we used to replace them from time to time on E46s and E39s because of hard failure (they stopped working completely). id ignore it for the time being as that is not whats causing your running problems. look for the typical M54 rough running stuff - plugs, coil gone bad, cam sensors, intake manifold gaskets, etc.