Fuel Trim A is at +15...ideas?

I have the same issue but runs stupid rich in boost. I've cleaned maf and it is reading right but didn't fix it. New af so i know that's not it but haven't replaced my rear o2 yet. All my vacuum hoses look good and are connected. I need to pressure test/smoke test to make sure no leaks as well.

A small vac leak will not necessarily throw off trims across the board. It becomes a smaller and smaller percentage of the overall as mass flow increases.

 

Your WBO2 reading 14.5 just indicates that the ECU is adding enough fuel to reach stoich, or close to anyways.

Ah that's scary! When i replaced all my vacuum hoses i zip tied or used tiny clamps on all the connection points to help prevent things from popping off.

Better to run rich than lean anyday

I'm not hi-jacking, but have the same problem. ~20% LTFT at idle. Initially rough with misfires and stall at times. Idles fine albeit low, and runs out good after what's been done below.

 

1. All vacuum hoses R&R'd, with ~1/8" cut from ends for nice tight fit, zip ties added where boost lives.
   
2. OE front and rear O2's (1yr old)
   
3. OE plugs (1yr old)
   
4. PCV Assembly (3 months old)
   
5. OE OCV x2 (noticeable smoothing of ending)
   
6. BG44k fuel treatment x2 over past year
   
7. R&R MAF
   
8. Upgraded fuel pump DW(forgot model) drop in... replaced and seated properly.
   
9. R&R'd engine grounds, cleaned and protected with liquid electric tape
   
10. Smoke tested to 14psi with zero leaks... (I'm luck, there's a great mechanic and a good guy close to me, Infamous Performance)
    
11. OE short block from Subaru with my heads machined and rebuilt.
    
12. Replaced turbo inlet with AVO (thinking the original had a tear... it didn't, was new replacement during engine rebuild.
    
13. Spray tested with pilot start while monitoring trims... NG
    
14. flooded the suspect connections with water (all of them) which revealed an area by the turbo was leaking. Separate post for the leack (it's in the TVG manifolds)
    

http://legacygt.com/forums/showthread.php/tgv-manifold-small-end-cover-vacuum-leak-236480.htm

 

No one has been able to identify the cause of the condition. It has improved greatly, but trims remain. Here I'm testing the FBR

http://legacygt.com/forums/showthread.php/tgv-manifold-small-end-cover-vacuum-leak-236480.html

 

 

After some brainstorming the consensus was too much air or not enough fuel (bad injectors, bad pump etc. Findings:

 

• At ~1450ft, at idel car has about 22in/mg, when that is applied to the FPR the pressure pump pressure remains 35%
  
• Whan adding 10-12psi shop air, pressure jumps to 55-56psi rock steady.
  

Seams the FP was supposed to be ~39-43psi at idle. if it's close but no cigar, is the FBR bad?

Honestly I've learned that, even though the little vacuum hoses look good, they can leak enough that they'll throw off your fuel trims. I had this same thing happen with one of the purge solenoid vacuum hoses, so I went ahead and zip-tied all of them and the fuel trims returned to normal.

So after pulling hair and nashing or teeth, I discovered a very small hole in the 1/8" vacuum hose which houses the pill. I only found it because I was moving the hose around a lot while dowsing it with water (while running) So the leak was under the clamp, and looked like a tack had made the hole at an angle. Repairing this leak as reduced my TRIM's by almost 10%!

 

The remainder for me is coming from the TGV shaft end cap. Both sides are leaking allowing a fairly substantial vacuum leak... but would alto allow pressure leakage. I'm working on how to correct it.

 

-C