Horrible Acceleration

[Danny3737]

I'm not sure how bad they would have to be before they would throw a code

 

[trox88]

Changed out solenoid. Light stayed off for about a day. Same code showed up again.

 

[rockola1971]

The circuit has to be tested with a smart scanner/programmer. Like a TECH 2 or an aftermarket equivalent. Like what the shops have. I have a tech 2 and it has command tests for the evap circuits. This isnt a simple check for 12 volts at wire blah blah blah because the evap circuits only get powered when certain engine conditions are met and the PCM commands them. A continuity test from PCM to EVAP solenoids and to ground along with a circuit ground are all in order first.

 

[HiHoeSilver]

Any way this could be a leak up by the fuel pump somewhere on top of the tank?

 

[rockola1971]

Any way this could be a leak up by the fuel pump somewhere on top of the tank?

Fuel pump is down in a sump area near bottom of the tank. There is a lockring and an oring on the top of the tank that holds and seals in the whole fuel module assembly. Leaking oring usually wreaks of gas smell especially when filled all the way up.

 

[iamdub]

I don't see the two things being related. One is just an emissions thing and driveability isn't affected an dthe other... well, I just don't see the PCM altering power based on OCI, especially after only a few hundred miles. I know the PCM slowly transitions to a lower octane spark table over time to compensate for the fuel in the tank losing it's octane rating. It factors in fuel level with time since last fill-up and knock sensor data to estimate the condition and octane level of the fuel. This wouldn't be noticeable in a vehicle driven daily, though. The only way the PCM would know that the oil has been changed is by the level sensor being tripped and by the Oil Life Monitor being reset. Maybe unplug the oil level sensor and short the contacts for a few minutes to mimic the oil being drained, reconnect it, turn the key "on", reset the OLM, then see if performance is restored for another few hundred miles.

 

[trox88]

Several days, two different shops, money down the drain, and nothing. Neither could tell me the issue. This is extremely frustrating!

 

[Fillerdust]

So for sure you notice a difference? I have a 4.8 in my Yukon and it's a dog. It is only alittle bit worse then I'm hauling my mustang on a trailer but not as much as you would think. The 4.8 is a dog but seems to have decent torque in my case. I have evap codes also but I can tell a huge difference in power just by the temps getting over 90 degrees and a/c on full blast.

 

[swathdiver]

Quit wasting money and take it to a competent dealership with mechanics familiar with your truck. Without a Tech 2, there's little you can do.