Lean condition / cutting boost

This one has me scratching my head. 06 LGT 5eat Pro tuned (speed density). Haven't been in boost above around 10psi in a week or two. So I figured I'd let her stretch her legs the other day. Well.... she fell flat on her face. I went WOT and when boost hit ~13psi it immediately dropped to ~8psi and held there. The car is tuned for 20psi. I logged a pull and as you can see from the log the AFR goes lean and boost drops. So first thought was vacuum leak pre turbo. After a cursery inspection I found no leaks. But it occurred to me that if I had actually gone lean due to a leak I would have had knock. DAM is at 1.00. So now my focus shifted to lack of fuel. I currently have a full tank so pulling the fp isnt an option right now. Trying to narrow this down in my head first. My fuel system consists of: AEM 340 pump, ID 1050x with top feed ID rails, parallel lines to Aeromotive FPR. Rewired fuel pump control as per Turkeylord/Underdogs post. I've been running like this for about 2 years and ~20k miles. I used a wifi cam to watch my underhood fuel pressure gauge realtime while making a pull and found it rose to ~60psi during the pull and held there till I let off. So it appears I have appropriate pressure. All pulls had Either 0 feedback knock or -1.30 (which I've gotten from time to time in the past). Probably phantom knock of some sort but so low...don't care. No FKLC. DAM at 1.00. So I think the fuel pump is fine and FPR is fine.

 

But can a fuel pump put out pressure but not enough volume if it goes bad?

 

Side note: I do have a UEGO and can see it leaning out to ~17-18 at the gauge so I know the upstream o2 isnt reading wrong.

 

My theory is that an injector is completely dropping out during WOT and allowing the cylinder to just fill with and pass fresh air along to the the o2 sensor which then sees a lean condition causing the ecu to pull boost. If there was any fuel present I'd think It would register knock.

 

Any thoughts or ideas on how to trouble shoot are much appreciated. If there's something I missed, let me know.

 

-Dave

lowboostdatalog1.csv

Solved.

 

So after discussing this with a mechanic it really made sense to be a failing fuel pump. So I replaced it. That didn't fix it. Hate the parts cannon thing so back to diagnostics. Next I pulled the plugs and inspected them. They all looked the same and gapped fine (only ~20k old). Finally it gave me an excuse to replace the connector on #3 coil as it's been zip tied for years now. After that I tested the car on wastegate spring only. Same issue. That also allowed me to rule out the EBCS. Tested the bypass valve. Worked correctly, not leaking under boost. Pulled the GS intercooler and inspected all the hoses. No problem found. Pressure tested the inlet and thats when I found what appears to be the issue. The soft silicone hose connected to the MAP sensor popped off during that test. Hmm... No zip tie! has the indent from being ziptied before. Threw on a ziptie and put everything back together. Did a test pull and no more problem. I'm thinking that the MAP hose was leaking at ~13psi but not blowing off. The leak must have been enough to get an improper reading at the MAP causing it to pull fuel creating my lean condition.

 

 

 

-Dave

Nice work on chasing it down. IF more would do what you did, there would be a lot less aggravation in questions on the forum. Obviously it stresses the importance we all know of zip tying our hoses in place.