2008 Tahoe Fuel Delivery Issue?

[iamdub]

No set codes when it does this but - the CEL does come on and flash until you let off the pedal. The mechanic did say he watched it command fuel but not get it and it went lean. He stated he had it hooked up to a laptop. Like you stated, everything else seems to respond like it should it just doesn't seem to get any fuel.

This changes things. Hook up a mechanical fuel gauge with a long enough hose to locate the gauge on the cowl and watch it while test driving? Maybe the fuel pump is losing power when the driveline torques? Kinda farfetched, though. Either way, I'm leaning toward an electrical circuit failure.

When he says "command fuel", does he mean the PCM raises the injector duty cycle?

 

[NarcolepticNugget]

This changes things. Hook up a mechanical fuel gauge with a long enough hose to locate the gauge on the cowl and watch it while test driving? Maybe the fuel pump is losing power when the driveline torques? Kinda farfetched, though. Either way, I'm leaning toward an electrical circuit failure.

When he says "command fuel", does he mean the PCM raises the injector duty cycle?

I'd have to ask him for clarification on that but this is becoming quite the nightmare vehicle.

 

[swathdiver]

The fuel system components can be tested individually with the Tech2. This will quickly expose the offending part.

 

[kbuskill]

Which engine do you have?

Is it Flexfuel equipped?

 

[NarcolepticNugget]

Which engine do you have?

Is it Flexfuel equipped?

5.3L & yes it is flex fuel equipped.

 

[swathdiver]

Should be an LMG iron block motor. Don't think they got the LC9 until 2010.

 

[kbuskill]

5.3L & yes it is flex fuel equipped.

I know the older Flex fuel trucks had an alcohol sensor to detect the alcohol content in the fuel. I'm not sure about the newer trucks. If it were giving an incorrect reading perhaps the ECM would be using the wrong fuel tables.... although I would assume the O2 sensors would try to correct it.

 

[swathdiver]

I know the older Flex fuel trucks had an alcohol sensor to detect the alcohol content in the fuel. I'm not sure about the newer trucks. If it were giving an incorrect reading perhaps the ECM would be using the wrong fuel tables.... although I would assume the O2 sensors would try to correct it.

Not the GMT900s. But if the Fuel Trims get out of whack as they did on another truck here recently, they can be reset by the Tech2.

 

[NarcolepticNugget]

I'll have to look into getting it scanned w/ a Tech2 but, as far as O2 sensors go - I only have Bank 1/2 Sensor 1 for each side as the rest were deleted/removed when I put my exhaust on. The downstream sensors were disabled via the tune.

 

[swathdiver]

You didn't by chance use any downstream sensors to replace an upstream sensor? They are different part numbers.