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1997 chevy astro van v6 engine
System too lean bank 1 and bank 2
Smoke checked for vacuum leaks and none found....fuel injectors, fuel pressure regulator, fuel filter, and fuel pump have been replaced..these items where faulty thats why they where replaced..one injector was bad, regulator was leaking and the pump was weak..... now there is dtc showing bank 1 & 2 are too lean... fuel trim on both banks are at +25...again i have looked for vacuum leaks but i cant find any...
Hi Hernandez530, welcome to the forum.
I think we would be in a better position to help if we knew a few things first.
When are the trims at their worst, and what are the trims @ idle, 2500 rpm, and while driving. Long term and short term for both banks.
Is there any freeze frame data to look at that could clue us into if this is happening under load, with the engine hot, cold etc.
It seems like you've pretty well gone through the fuel system, I'd still want to know what fuel pressure looks like at various loads...and....
up stream o2 sensor readings.
Also MAF is suspect for a lean condition, but we could look into that further depending on how the rest of this plays out.
Thanks for the replay Noah
It seems that Fuel trim gets worse when i accelerate the engine and its the same on cold engine and warm engine
At idle (bank1) St fuel trim is at 10-12
And Lt fuel trim is 22-27
At about 2500 rpm
(Bank1) St fuel trim is 25-33
And Lt fuel trim is 27-35
Bank2 is pretty much identical to bank 1
If i snap the throttle St fuel trim on both banks goes to 0 for a split second
If i press the brake pedal and shift into reverse or drive the engine seems to bogg a little
Fuel pressure is at 50psi at idle and if i snap on the throttle it goes up slightly
It seems that Fuel trim gets worse when i accelerate the engine
Then I'd go in the direction of fuel delivery, MAF sensor,....
Agreed.
Minimum fuel pressure spec for this engine is 60psi.
60 to 66 is the operating range.
Considering the pump, the filter and pressure regulator have all been changed, unless there is debris in the tank plugging the strainer, you could be looking at a voltage drop in the fuel pump circuit.
I was thinking maybe a pressure regulator allowing to much fuel to return to the tank, but you said you changed it. Testing it could be difficult, I believe it's under the intake on this one?
If you're only showing 50ish psi at idle that's where I'd focus. The fuel system needs to run 58-66psi. Around that 50psi range the injector poppers will barely open.
I have a 1996 Tahoe that had similar problem and it would up being a pinched fuel line.
I'd check for excessive pressue decay and maybe graph fuel pump current. Check power and grounds at the pump to. These were known for connector issues at the pump. Most pumps were sold with a wiring update and the crappy style butt connectors.
Spot on Noah. Fuel Pressure is too low for this system.
His symptoms match this as well.
Then I would focus on MAF as Dylan suggested. These model GM's have a very good back up strategy for a disconnected sensor.
Hernandez530 wrote: Guys..to check of the engine is starving for fuel can i spray some starting fluid or propane in the air intake to see if the fuel trim gets better?
The test you describe would not prove the engine is starving for fuel, but would help determine the condition of the oxygen sensors.
If you add a secondary fuel source to the intake, the fuel trims should go negative and the upstream o2's should go rich. I would expect something above 800mv, or 0.8v.
If the o2's and fuel trims do not respond appropriately, then the o2's are at fault.
I'm still in the same boat with Chriscoy and ScannerDanner about needing to investigate that low fuel pressure further
I just tested the mass air flow sensor it seems to be working properly.. i used a multimeter to read the frequency...at idle it was at about 2k hz
And increased as i opened the throttle, i didnt see it glitching or bouncing around either...what im thinking is that the remanufactured injectiors that i bought are not flowing enough fuel...
i dont think fuel pressure is my problem because before i replaced the pump it would run at 38psi and i didnt have this problem
So its not a mass air flow issue for sure...i replaced it with a known good one from a friend....her is a picture of fuel trims and fuel pressure at idle...
Hernandez530 wrote: So its not a mass air flow issue for sure...i replaced it with a known good one from a friend....her is a picture of fuel trims and fuel pressure at idle...
That fuel pressure is too low brother...
You're not going to get anywhere with this one until you get to the bottom of the fuel delivery issue.
just noticed that the fuel pressure drops immediately after i turn the ignition off...doesnt hold pressure for even 1 second.. bad fuel pressure regulator? Or fuel pump check valve?
They are both new so i dont know whats going on here
Hernandez530 wrote: just noticed that the fuel pressure drops immediately after i turn the ignition off...doesnt hold pressure for even 1 second.. bad fuel pressure regulator? Or fuel pump check valve?
They are both new so i dont know whats going on here
Could be either one! You'll need to either pinch off hoses or install shut-off valves to tell which. I offered a decent explanation to Gilbert in this thread, check it out:
Hernandez530 wrote: Just removed the upper intake plenum..the fuel pressure regulator is good i tested it with a vacuum pump...
So, you put a vacuum pump on the regulator itself, and it held vacuum? I understand the test, but I'm not sure that it guarantees that the regulator isn't bleeding pressure off when it's supposed to be closed.
The easiest way to prove this would be to block the return line and pressurize the rail. If the pressure now holds with the pump off, then your regulator is suspect. If it does not, then you're going towards the fuel pump.
So, you put a vacuum pump on the regulator itself, and it held vacuum? I understand the test, but I'm not sure that it guarantees that the regulator isn't bleeding pressure off when it's supposed to be closed.
The easiest way to prove this would be to block the return line and pressurize the rail. If the pressure now holds with the pump off, then your regulator is suspect. If it does not, then you're going towards the fuel pump.
Totally agree with Tyler and Noah. After reading the other posts something's wrong here in the fuel circuit.
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