It could be an electrical issue so I am not putting that aside. I have combed over the engine bay, under the dash, and done some work. I replaced the neg (-) battery cable bc its fit on the battery would not tighten properly. I removed what grounds I found in the vicinity of the battery and the engine fuse box, there's a junction just behind the battery fwd of the fuse box, and cleaned them using a wire bit I have specifically for grounds. I checked all the wiring going to the fuse box as well as the majority of the engine wiring harness. Didn't find anything but repaired the wire harness/protective tubing as I went. I have to figure out why the WS wipers, heated seats, and such aren't working any ways so I plan on going on a ground search.
I have not seen any ground wires in the vicinity of the ignition coils so I will look into that this weekend and see what I find. If that's the problem you'll be my new best friend, this has been going on what feels like forever.
Thanks
Rob

 

Don't feel bad, if the diagnosing and repairs were easy you would be driving a Chevy. I'm still dealing with random P1174 and P1171 codes despite a new MAF and PCV valve. I have sprayed carb cleaner and get no change, and smoke tested it. I think that some times you just have to chuck parts at it. Stupid but at least your not paying for labor.

 

If you can't find any vacuum leaks, you may want to go after fuel. I forget what the spec is, but if it's down on fuel pressure that will also give you lean codes.

 

So disc oh no,
Are you saying that a drop in fuel pressure will trip lean codes? I would have thought that a clogged injector would lead to a misfire for a specific cylinder. If I understand your thinking, a general drop in fuel pressure will trip a "generic" lean code like 1171 and 1174? So it might be the injector rail or general fuel pressure? With pressure being an issue, could it also be the fuel cap is not creating a proper seal?

 

The fuel cap should not be an issue. The fuel system is vented to atmosphere most of the time anyway. The only time it's sealed off is when the computer is running the evap test.
Yes, low fuel pressure can cause these codes. Usually, with lean codes on both banks, I check for vacuum leaks first. If I don't find anything there, I go after fuel pressure. That is not to say these are the only two things that can cause these codes. They're just the most common.

 

Clogged fuel injector generally means that it is spraying rather than misting. I don't think that would affect fuel pressure, nor would a non functional fuel injector. The pump would just have an easier time maintaining pressure with a non functional one.

 

I will have to get a pressure gauge to see if I can get a read on the fuel pressure. That seems like a difficult test to do. Can it be done with the upper plenum removed, Im not sure I can get to it otherwise.

thanks

Still working the issue, while trying to fix electrical problems

 

You can do it with the plenum off easily. But doing it with the plenum on would be hard. If you take the plenum off just charge the system by turning the key to position two. Don't turn it on. Lord I did that once and barely got the ignition off before it blew up.