Hi everyone. I’m hoping to get some help tracking down a lean condition. I believe it’s a vacuum leak, most likely caused by this little divot in the head right by the #3 intake port in this picture:
http://audirevolution.net/addons/albums/images/276529851.jpg
I caused that when I was struggling to get the IM back on and accidentally dropped it, and a corner landed right in that spot and made the dent. It is fairly small, but it goes all the way across and I think the photo makes it look smaller than it is. I’ve tried confirming that this is the source of the vacuum leak by spraying propane under the IM on that bank while watching the fuel trims in VCDS. It’s kind of hard to do since I don’t have direct access to that side of the intake ports, but if I spray under the manifold, regardless of whether I’m spraying from the front or from the back, I can see the fuel trims for both banks going down to adjust for the extra fuel. I’ve already re-checked all of the IM bolts and none of them are loose.
To give some background info, I pulled the engine and did the timing job not long ago. Before I reinstalled the IM, I put a small dab of permatex #2 non-hardening sealer over that dent, and then used a new set of aftermarket (paper) IM gaskets. It seemed to be running perfect for at least 2k miles after that. I didn’t check fuel trims at that time and I can’t say I fully trust my butt dyno, but I wasn’t getting any cels at all and the power seemed fine.
The thing that seems weird to me, is that everything I’ve read online says that a vacuum leak should be more lean at idle, and less lean under load. For the long term fuel trims VCDS is telling me that adaptation (idle) is about 7% and adaptation (partial) is about 15%. If I understand those numbers correctly, that means that my engine is going more lean under higher load/rpm, which points to a fueling issue instead of a vacuum leak. Is that correct?
another possible issue I have is that my fuel pump makes a juddering noise which I have heard is fairly common. Shortly before I did the timing, I replaced the fuel pump and filter with brand new genuine parts but it still continued to make that juddering noise, although it only happens on startup and goes away after driving a 1/4 mile or so. I’ve seen a lot of conjecture over on audizine about this juddering noise possibly being a sign of a failing pump, but nothing definitive. It would be odd if this pump is the cause since it’s new.
soooo… sorry this is post got so long btw but can anyone more knowledgeable help me out here? Is it possible that this is just a vacuum leak even though it gets more lean under load?
these are the codes I’m getting:
17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 001 - System too Lean - Intermittent - MIL ON
17538 - Fuel Trim; Bank 2 (Mult)
P1130 - 001 - System too Lean - MIL ON
16891 - Idle Control System RPM
P0507 - 001 - Higher than Expected. - Intermittent
17544 - Fuel Trim: Bank 1 (Add)
P1136 - 001 - System too Lean - MIL ON
17546 - Fuel Trim: Bank 2 (Add)
P1138 - 001 - System too Lean - Intermittent
18359 - Radiator Fan 2 (V177)
P1951 - 001 - Movement Restricted / Jammed - Intermittent
TY in advance for any assistance!