If the fuel pressure is supposed to be 41-71 psi and I have 38 at idle and 46 when the regulator's vacuum line is removed, is that a clogged filter (it's six years old) or is it the fuel pump?

The leaking fuel injector couldn't cause that fuel pressure drop correct? I mean it is a leak that simply gets the aluminum where the injector is set and doesn't spray or run at all, though I will be resetting that one with a new o-ring to insure the leak is gone. I cannot imagine it lowers the pressure much at all.

Dave

Dave

 

I replaced the fuel filter, but the psi readings of 38 idle and 46 with the vacuum line off the regulator on idle stayed the same.

I'm thinking fuel pump.... sound right?

 

One area I am not aware of on the Lumina, regulator. I am familiar with 5.3 fuel pressure regulator. Is there gas in the vacuum line to it? If so, The diaphram is leaking. What an injector leak tells me, the ecm has fuel schedule based on a few parameters, and that cylinder should be the same as the other 5, but mechanically it is not, because of the low fuel mixture( due to leak) in the cylinder.

 

When I last had the code pulled, it was PO300.

I kept getting the idea it was the fuel pump, so I replaced it. The fuel pressure is the same and a few muscles in my arms are sore in some crazy places, haha.

It's obviously something else.

 

I will let you know that a 5 minute drive post fuel pump replacement gave a notably better drive as she went up the hill outside the neighborhood without issue or bogging down. However, I couldn't drive it long enough to get her hot and see how she does. I might be over analyzing it, but it seemed when I almost got back to the house, she bogged down a bit on a flat, but a slight pedal nod and she picked up speed again. Anyway, I'm taking her out this AM and will make sure I tests her hot as well as get the o-ring(s) replaced to fix that leak around injector #1.

The engine service light was not on BTW.

The CAT has come to mind, but we'll see when she's hot.

I so want to be done with this car and get my truck back.

1,000 thanks again for assistance troubleshooting her.

 

I just had the CAT checked and you can see light go right through it, so that's not an issue.

Interestingly, she started acting up once the engine was hot, and now she bogs down under load like before. So, it's heat realted and something is messing with the fuel/air mixture because of that heat.

Ideas? Thanks in advance once again!

 

Look at the plugs, do they look normal, carboned up, oil fouled?

 

The plugs are clean and good, they were installed with a new set of wires when my daughter alerted me of her issue, the other ones didn't look bad at all really.

I just disconnected the MAF sensor and let it warm up and drove it. No change in the loss of power.

I then took it to a highly recommended transmission guy who said over the phone he'd give me a diagnosis for free. He stated that there is a spring and a valve that has been known to get gummed up and cause the very issue I described. I'm kinda at a loss now, so we'll see what he says and what else guys like you can do to assist.

I really appreciate all the feedback... this is a real hard -and frustrating- problem of which to find the actual cause.

 

Thanks!

 

Turns out, testing the MAF is not easy. I checked for power and signal, cleaned it (thought it wasn't very dirty) and ran her with it disconnected and nothing told me anything, she hasn't thrown a code since I replaced the fuel pump.

But I replaced it, and she drives as designed now.

Go figure.... it was the final piece that had absolutely no indicators.

Thanks for your assistance!