Fixes and.then maybe not!

[Livebai8]

Your engine will have an actual fuel composition sensor, and if that's wacky -- one of my oft-used technical terms -- the PCM may have switched to the ethanol tables, codes or not. The sensors are not cheap, and you might look for a way to disable it if the facts point to an issue with it.

Although you'd see this in excessive fuel trim values (as in the video) it wouldn't hurt to check to see if you can view the sensed ethanol % on a scan tool.

The more info you have, the more likely you'll be able to diagnose it. Personally I think you have a vacuum leak that changes with warmup, but that's a WAG on my part, due to the information I have at hand.

I guess I need to find someone with a scan tool like that but until then I'll check foe vac leaks.

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[Livebai8]

I guess I need to find someone with a scan tool like that but until then I'll check foe vac leaks.

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I only have a code reader...but not throwing any codes at all.

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[Livebai8]

I only have a code reader...but not throwing any codes at all.

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I found this inexpensive scan tool that'll read the fuel trims. Anyone using this one? The reviews were really positive.

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[Livebai8]

I haven't checked FP just yet...but I am in Tahoe now...at start it would idle but dies when putting gear...it did this several times up until I was able to travel a mile or so before coming to a stop...it hesitated a bit but didn't die out...got on hwy at 65 for about three miles before coming to a light and truck idled at 500 and at 500 now in parking lot. When dropping into reverse idle fluctuated down to 400 but back up at 500 but not dying out.

I'll check FP later this evening after cool down and dinner.

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Ok...key on pressure read 42psi and slowly dropped to 35psi...truck running pressure reads at 42psi to 44psi. Not near the 48 to 52 psi...so I'm assuming I have a vac leak somewhere...question is where? My egr thing bolt is tight but the piece is loose? Or is that how it's supposed to be?

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[Jeff O]

Check this out, but I believe the existence of an inline fuel filter means you have a flex fuel engine. If so there is a sensor mounted on the driver side of the transmission which senses what percentage of the fuel is gas or alcohol and adjusts engine timing and engine computer parameters. Straight gas engines don't have an inline fuel filter, it's in the tank. A bad fuel sensor can not only cause poor performance, it can totally stop the car from running or starting.

 

[Fless]

Low fuel pressure can be caused by a few things, as @Jeff O mentioned, the fuel filter, damaged fuel line, also a leaky fuel injector, bad fuel pump, etc.

 

[Livebai8]

Low fuel pressure can be caused by a few things, as @Jeff O mentioned, the fuel filter, damaged fuel line, also a leaky fuel injector, bad fuel pump, etc.

Yeah...gonna get the fuel filter changed out once I get the proper tool...and yes it is flex fuel. Truck ran fine yestetday...but showed same symptom earlier this afternoon...running fine now so I'm hoping it filter related...and no codes.

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[Tonyrodz]

I found this inexpensive scan tool that'll read the fuel trims. Anyone using this one? The reviews were really positive.

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That's a good price.

 

[Rocket Man]

Check this out, but I believe the existence of an inline fuel filter means you have a flex fuel engine. If so there is a sensor mounted on the driver side of the transmission which senses what percentage of the fuel is gas or alcohol and adjusts engine timing and engine computer parameters. Straight gas engines don't have an inline fuel filter, it's in the tank. A bad fuel sensor can not only cause poor performance, it can totally stop the car from running or starting.

02 gas engines also have a fuel filter inline, under the driver along the frame. My 02 Denali does.

Yeah...gonna get the fuel filter changed out once I get the proper tool...and yes it is flex fuel. Truck ran fine yestetday...but showed same symptom earlier this afternoon...running fine now so I'm hoping it filter related...and no codes.

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What tool are you referring to? The filter is under the driver on the frame rail and all you need it wrenches to replace it.Unless yours is different from my 02 Denali?
Edit: I see the flex fuel has the quick connects.

 

[Livebai8]

02 gas engines also have a fuel filter inline, under the driver along the frame. My 02 Denali does.



What tool are you referring to? The filter is under the driver on the frame rail and all you need it wrenches to replace it.Unless yours is different from my 02 Denali?
Edit: I see the flex fuel has the quick connects.

Yeah...the disconnect Tool. I just got my Lisle low profile disconnect Tool in the mail.

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