Intermittent Injectors on Rear Bank?

[DoctorDex]

The thing is, is that I can replicate run after run. It always seems to do the same thing. This leads me to think its not a bad connection.

I've been thinking maybe I could have a stuck wastegate, or worst case scenario, bad rings on my rear bank? Does anybody know how bad rings present?

[grtn316]

If your seeing knock and seeing timing pulled then I doubt its the o2 at fault.


*EDIT*: how much knock are you seeing? If that o2 is accurate I would bet its ALOT @ WOT.

[DoctorDex]

Originally Posted by grtn316

*EDIT*: how much knock are you seeing? If that o2 is accurate I would bet its ALOT @ WOT.

Seeing quite a bit of knock. However, once in a while, it won't knock and it'll pull well, an example would be the WOT I run I posted above. All other attempts at making a WOT had to be aborted because of too much knock.

I pulled the downpipe to verify the lean condition and my rear bank is white (very lean) whereas my front bank is black (rich).

Anybody have any suggestions or ideas?

Declan

[mehlosTT]

Jeesh_ relax kids_ think horses not zebras when you hear the hoofbeats pounding close.
rear bank runs leaner and_ it has newer O2 sensor.
1st: when those O2 sensors start to go, they read richer then reality, so they lean the fuel out. The log suggests it is working okay as there aren't the O2 dips before going leaner ( correct?)
if so_ then when not under higher fuel psi, she runs leaner. And it is not always exactly the same but fairly close each time.
Runs fine when she has more fuel psi like at boost? , as in when rpms are going to be above5000 or more can mean that when NOT under boost, the rear injector or all three even, can have some spray pattern irregularities_ minor clogging. But>..don't forget the obvious other factor.....a poor fuel pressure regulator that is not maintaining enough fuel psi is letting too much fuel by- pass back to the tank, coupled with less then perfect spray injectors..well?
Try this before going nuts with new parts_ one can of really good Injector cleaner that doesn't leave future residual build up.
then get a nice new cheap OEM regulator unless you of course already have an adjustable regulator.....if so, try the injector cleaner first and check check check the O2 sensor's connector , specifically the green wire which is the O2signal wire's ground. Curious to see which thing was the culprit.

[DoctorDex]

I'm curious if the screwy voltages I'm seeing on my rear bank could be caused by a leaking EGR valve. You'd think if an egr valve was leaking, boost would be pouring into the exhaust, up until the point the back pressure from the exhaust equalized with boost pressure (6000+ rpm @ WOT). This would explain why I see a lean rear bank that seems to be proportionate to the amount of boost. I disconnected my EGR to see if this would fix the problem and this seems to have made the problem worse.

I'm going to try an EGR blockoff to see if this fixes the problem.

Declan

[AudioPmp23]

Before spending money on the blockoff plates, run to a auto store (or a Harbor Freight if you have one there) and get a "brake bleeder & hand vac pump" kit. I got one for like 20-25 bucks and it has a gauge on it.

With this you can test the wastegates, egr valve and every other solenoid on the car.

It also gives you the capability to trace down leaks that you can't even hear. (My boost gauge was leaking pretty bad, but I couldnt even hear it at all, )

Back to the EGR valve...the passages should remain sealed at rest. I believe it should start to open the needle around 1.2 in/Hg...I'll have to verify that. And also it should hold vac steady at about 16 in/Hg +

[DoctorDex]

I turned the boost down to wastegate pressure (7 psi) and the knock goes away, but rear O2 voltages stay the same.

[DoctorDex]

I tried some other runs today, with and without the EGR connected. However, I didn't do back-to-back-to-back runs so there could other factors affecting the results. Here is what I found:

EGR connected with 7psi Boost - No lean condition
EGR connected with 12psi Boost - No lean condition
EGR connected with 16psi Boost - Lean rear bank

EGR disconnected with 7 psi boost - lean rear bank
EGR disconnected with 12 psi boost - lean rear bank
EGR disconnected with 16 psi boost - lean rear bank.

These results lead me to think that my EGR is leaking boost into my exhaust. The problem seems to be worse when I disconnect the EGR. With the EGR disconnected it _should_ be closed all the time, but this does not seem to be the case.

I guess the only way to confirm this theory is to do a pressure test and then unbolt the EGR pipe from the back of the intake to see if boost is leaking out of the EGR valve. I don't have time to do this at the moment, but I will try and get around to testing this theory next weekend.

Declan