Leaking injector O-rings

[V8weight]

I've been chasing some issues with my car for a while, where there was an intermittent sudden drop in specified load under boost or moderate throttle. The car would suddenly drop specified boost and close the throttle valve to 50% without reason. I finally found a trend in my logs where the MAF g/s would start to see-saw when the throttle cut occurred, and I also found that the knock voltage was a bit high on two cylinders. Here it is: I had two injectors that were leaking out of their o-rings, causing an almost untraceable vacuum leak.

Here you can see the engine harness disconnected and the fuel rail removed:
http://i722.photobucket.com/albums/ww228/Pellis833/002-21.jpg
Here you can see the injector inlets on the manifold. The film is a tell tale sign that both air and gas were sneaking by.
http://i722.photobucket.com/albums/ww228/Pellis833/003-20.jpg
http://i722.photobucket.com/albums/ww228/Pellis833/004-20.jpg
Here's the injectors that were leaking, as seen by the film above the O-rings:
http://i722.photobucket.com/albums/ww228/Pellis833/005-18.jpg
http://i722.photobucket.com/albums/ww228/Pellis833/006-15.jpg
And here's a shot of the fuel rail.
http://i722.photobucket.com/albums/ww228/Pellis833/001-17.jpg
The car runs great now, no more partial throttle uncertainty, the car is consistent in the way it reacts to throttle input now, and so far no more throttle cut!

[DonS]

Congratulations. Your deductive reasoning from the data seems better than my dealer mechanic...

[V8weight]

Congratulations. Your deductive reasoning from the data seems better than my dealer mechanic...
Speaking of dealer mechanics, if they would have replaced these O-rings as the manual specifies when they did my after run coolant pump, this thread wouldn't be happening right now.

[MaxRS6]

Nice pics and info- Congrats on finding the issue!

[ben916]

this forum keeps getting better and better!

[JSRS6]

So that's what was causing the one bank to drop and the other to not in the graph, huh? I thought that looked weird.

[V8weight]

So that's what was causing the one bank to drop and the other to not in the graph, huh? I thought that looked weird.
No, that actually has to do with sampling rates. Like I said, under closed loop, the lambda voltages are in a constant wave swinging from 0-.8 volts about 10 times a second. When I kicked the car down and it started to go into open loop, the bank one voltages happened to be at 0, while bank 2 was in mid stroke. They both got the message at the same time, and moved from their respective voltage up into the .8's. It just has to do with bank 1 being sampled before bank 2, and the associated lag in data.

[JSRS6]

If you don't learn something new everyday, you are doing something wrong. Thanks.

[V8weight]

If you don't learn something new everyday, you are doing something wrong. Thanks.
Same here, I know I've been chasing this issue for quite a while, and have done hundreds of data logs and found most of them to have no relevant data in relation to the issue. As I learn more, I look back at those old logs that I've discounted, and suddenly there's discrepancies popping out of the data everywhere, I just wasn't looking for it. I was going to tell you that you were looking too far into the graphs, but when I thought about it, it's actually an attribute. Had I looked a but deeper, I could have figured this out months ago.

Alright, I'm outta here, off to a bachelor party, Cheers.

[V8weight]

Still running strong today, I think I finally have this monkey off my back!

[JSRS6]

Awesome Pat. Great to hear. I got the wrong t-clamps in the mail, they are sending me the right size. They sent 3" min dia. Instead of 3" max. Oh well, I retested the sealed intercoolers and they are solid. Can't wait to install them.

[4everRS]

This is good news Pat. How did you figure to check the injectors? It wasn't by chance on a Porsche forum was it?
Still running strong today, I think I finally have this monkey off my back!

[V8weight]

This is good news Pat. How did you figure to check the injectors? It wasn't by chance on a Porsche forum was it?
Porsche forum?? Basically the data was telling me that I had unmetered air entering bank 1, and more specifically, cylinders 2 and 3. My first thought was intake gaskets were the only thing that have a leak isolated to single cylinders. As I proceeded remove the air cleaner and inspect the intake, the film surrounding those two injectors was immediately evident. I replaced all 16 o-rings for about $34, so all in all a cheap repair. P.s., this was the cause of the silliness that you felt while test driving my car a Cars and Cafe.

[4everRS]

I know you've been studying up on the P cars so I thought maybe you've seen P car owners that have dealt with this.