Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Hey SJ... held my foot on the brake peddle and it dropped when it started. At warm idle pressing the brake didn't change anything and neither did unplugging the MAF sensor. I wish my fuel pressure gauge tester had a longer line so that I could watch the fuel pressure as I drove it under load. SMH this is going to be something so simple when we find it I bet.
Brake pedal should not drop, should bump and be firm. A leaking brake booster can cause lean problem. Test buster further don't just replace it. Clamp off booster vacuum line then check trims.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
Being wrong doesn't bother me, it's being right and not understanding why that does
Here is a simple and cheap trick that I have used to make a fuel gauge longer:
Cut the hose about in half
Go to the auto parts store and buy a piece of metal brake line that is the right size to tightly slip inside the hose on the fuel gauge.
Get two fuel injection clamps of the right size and put them on the fuel gauge hose
Tape a wad of towels just under the face of the gauge, that way you can put the line under one of your wiper blades and have the gauge face down on the windshield while driving without chipping or breaking the windshield
Set up a video camera and record it while you drive
You can bend the brake line to make it go where ever you need and it won't leak. Just don't kink the brake line.
Super cheap, easy to do and gets the job done.
Use a camera though. Trying to focus on a fuel gauge while you are horsing it ( probably doing 55mph on a back road ) is amazingly dangerous!
I went back and re-read all the posts on this... you mentioned a couple of time that you replaced the MAF, a couple of times, BUT you have never posted the MAF readings. What is your MAF g/s on hot idle and voltage.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
Being wrong doesn't bother me, it's being right and not understanding why that does
Could be a stretch, but isn't there an alcohol sensor of some sort under the vehicle on these? Could there be a problem there that could be throwing off the mixture? To be honest, I'm not really sure how they work or what they impacts. Just thinking/typing out loud.
Never really heard of that through doing everything else to this stupid truck. I know earlier in this post ScannerJohn mentioned T 5.3 motors are gas only and Z 5.3 motors are multi-fuel. I have the T motor. Is that what you're talking about?
Hey SJ... I didn't find the volts reading on my scanner. I'll recheck it today to see if it's on a different screen on my scanner. But this is what I found at Hot Idle, Loop is closed... MAF = 5.87 G/S and 2643 Hz
Yeah, I had a GM 5.3 in one time where I replaced some alcohol sensor or something that was under the car maybe half way back on the driver side. Actually, no. It was a broken wire to that part. I imaging it was a flex fuel vehicle though.
Yeah I will do that water test again SJ... I can't believe how impossible this is getting with this stupid truck. All the injectors were replaced with new O-rings but like I said I'll do the water test again.
Question... In one of the new fuel pumps I had put in came with a new electrical connector for the fuel pump. Could that old fuel pump connector be bad?
their is a complicated current test that can be done with the fuel pump to show that the pump motor is providing the proper RPM's to supply fuel, but with your pressure readings being what they are I'm going to say that's not the problem. It cannot hurt in anyway to check the connection to insure good contact.
At this point patience is the key... there is an air leak somewhere, finding it will take time and systematic testing. Keep a log of what vacuum lines and components you have checked. I was looking for a diagram of the vacuum lines and components for the 5.3 but I do not have anything to share. Positive 30 total trim is quite significant, we are all missing what it is.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
Being wrong doesn't bother me, it's being right and not understanding why that does
Thanks for your help because at this point I don't know where to even start now. I thought the miss on cylinder 6 would've went away with the intake gasket change. But, it still acts the same. I have other cylinders that miss but nothing like #6. I've changed the plug, coil and wire and it didn't make a difference. compression was 135 psi. I didn't check the compression on the other cylinders... figuring it's not broke so why screw with it.
I remember on an even older Chevy Silverado was throwing a code... can't remember the number... it was some kind of vent underneath the truck by the gas tank. It wouldn't be anything down around the gas tank would it?. I never thought to crawl under there to look for smoke around the lines down there.
I would check the compression on the other cylinders, so you have a reference point. If the others have 200psi, then that would be a low cylinder and certainly have a problem.
Hey SJ I did a smoke test again, a much better day today to do this, and this is all I found top and bottom of the truck. The only smoke I saw seeping out was the throttle body shaft. And a very small peep of smoke from the fuel regulator. Otherwise nothing else jumping up and down waving at me.
I'll check the compression next... Now this is going to sound stupid but don't you just hook the gauge up and turn the motor over several times. Then check the gauge again? I ask because the mechanic helping me over the internet had said to check the compression but don't let the motor keep turning it over and over. I would think that 3-4 revs of the motor or where the needle on the gauge doesn't get any higher is what I've always done... anyways.
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