[mikal9913]

Alright guys,

So just some background to start. I've been driving my 08 335xi for about 3 months now. I bought the car used with 90k on it. Im nearly at 97k miles now. Since roughly about 3 weeks after I purchased the car I've been relentlessly chasing 2 Check Engine Light codes.

P0012 Intake Camshaft Position Sensor Over Retarded
P0303 Cylinder 3 misfire

So far what I've done to try and fix these problems;
-Replaced intake cam position sensor (also replaced vanos solenoids)
-Swapped Cylinders 1 and 3 Ignition Coils (And surprise! The misfire didn't follow the coils.)
-Replaced the spark plugs
-Replaced the number 3 fuel injector.

All parts were purchased directly from my local BMW dealer.

Basically how it started was that I was getting the P0012 code and ended up replacing the Cam sensor and VANOS solenoids based off of research. The car was doing fine for a while until recently at a cold start the car was misfiring on cylinder 3. When this occurred I swapped coil positions and cleared the code. It was fine for about 2 days. Then as I was leaving work getting out of midnight shift again the car threw a code for a misfire on cylinder 3, once this occurred I replaced the spark plugs and the car seemed to run a little better even though the old plugs didn't look to be in poor shape. After doing this I've still been noticing a misfire at idle for a few days and a slight break up when driving and applying throttle in higher gears (I.E. 50-60mph in 6th gear). Then today the car felt normal as I was driving to the gym and now out of nowhere after being off for over a month, P0012 code came back!

I was planning on getting the walnut blasting done this week, but at this point I am completely lost as to what could be going on that is causing these issues. If anyone has any guidance please let me know what you think!

[mikal9913]

No advice on this at all?

[BashShah]

Should have done the walnut blast before any of the things you already did.
Number 1 cause for miss fires.

Also when you replaced the injector, did you code it?
That is a must.

Do you know when the last time a walnut blast was done?
Get a borescope done on the intake ports to see how bad they are. (Ask for pictures of your ports)

After walnut blast, do a full adaptation reset.
Considered tranny oil and filter change also at your current k also.

DN