Mk6milli
New member
So I've had my 2010 golf 2.5l for a little over a year now and looking into things a little further now, I've noticed I am running lean. The car has had the cat removed and a new catback dual-tip exhaust from rev9 (don't judge me I was broke when I "upgraded"). It also has a CAI installed and the engine cover has been removed so the SAI tube has no inlet and I have it running with just a small cone filter on it. It's always run not so great but recently I started developing a misfire while under acceleration and at idle. I've replaced both o2 sensors, spark plugs, all coil packs, fuel filter, and MAP sensor.
So my questions are:
1. Would the engine cover missing be the cause of why I'm running lean all this time? I know that there are multiple reasons I may be but was curious about this because I know the engine cover is built into the car's intake system somewhat and without it I am missing a few of the sensors that were once there.
2: The misfire has developed randomly and as stated above I've replaced all parts I could really assume would be causing the misfire. I am replacing the valve cover soon as it is leaking from the back of the head and dried up oil all over the spark plug tube areas. I also did a vacuum delete kit by Spulen and noticed that the hose connected to my PCV on the valve cover to my intake and splits into my brake booster is leaking from the PCV into my intake manifold.. I'm trying to get a little info on what may be causing this to run so poorly or just any advice or info that may help me understand how to keep my car running at its peak performance.
I do not know a whole lot about these 2.5 engines and am hoping someone here has some more experience and info that may help me. I'm pretty handy and can replace most parts myself so I've been trying to avoid the shop route which is a pain because diagnostics is not something I'm great at.. Sorry for the jumbled and somewhat poorly written stuff from above. If anything is unclear or anyone has anything I need to be more specific about please let me know. Thanks in advance!
So my questions are:
1. Would the engine cover missing be the cause of why I'm running lean all this time? I know that there are multiple reasons I may be but was curious about this because I know the engine cover is built into the car's intake system somewhat and without it I am missing a few of the sensors that were once there.
2: The misfire has developed randomly and as stated above I've replaced all parts I could really assume would be causing the misfire. I am replacing the valve cover soon as it is leaking from the back of the head and dried up oil all over the spark plug tube areas. I also did a vacuum delete kit by Spulen and noticed that the hose connected to my PCV on the valve cover to my intake and splits into my brake booster is leaking from the PCV into my intake manifold.. I'm trying to get a little info on what may be causing this to run so poorly or just any advice or info that may help me understand how to keep my car running at its peak performance.
I do not know a whole lot about these 2.5 engines and am hoping someone here has some more experience and info that may help me. I'm pretty handy and can replace most parts myself so I've been trying to avoid the shop route which is a pain because diagnostics is not something I'm great at.. Sorry for the jumbled and somewhat poorly written stuff from above. If anything is unclear or anyone has anything I need to be more specific about please let me know. Thanks in advance!