07 Tahoe LTZ gas in the oil

[Marky Dissod]

... failure of the ecm to deactivate the injectors of the 1,4,6, & 7 cylinders could be the cause of my gas-in-the-oil tragedy.

There are two more likely scenarios:
1: Cylinders 2, 3, 5, & 8 (the full-time cylinders) do have to fire slightly more fuel when in V4 mode to drag the part-time cylinders along for the ride.
This gets worse as the engine gets older because the part-time cylinders spend much more time cooling off and warming back up.
Eventually you've a pair of V4s sharing a common crank, and the lazy V4's cylinder glaze and rings erase any MpG advantage, nevermind increased oil consumption,
and ...
2: If the rings for cylinders 1, 4, 6, & 7 are not sealing properly, when the injectors fire, some (more) fuel is going to sneak past those rings,
even if the injector spray pattern atomizes well and the injector closes when it should. Rings coked up with solid carbon don't seal well.

All the plug-ins do is tell one or more little white lies (technically) to the ecm, so the ecm declines to allow the Engine to Half@$$.
Mind, that's a good thing! - I'm just oversimplifying how it does it. Same applies to A.S.S. - they're not disabled, only disallowed so long as they stay plugged in.
That's the other reason you unplug them when you go to the dealer: optimists who left them plugged in for the dealer to find,
have learned by now to recognize their presence by hooking up a scanner and recognizing what they do.

 

[dkad260]

After a double flush

What did you do and use for this 'double flush"

So what I have gathered is you did cold starts then idle as this has been pointed out as one likely cause. With the "flush" did you use solvents? Perhaps the odor is from first the fuel dilution from the cold starts, then from any residual odor of the flushing chemical if any was used. You could try using some Valvoline Restore and Protect 5W-30 and see if that may resolve any possible sticking ring issues which could be the casue of fuel dilution.

The fact you said the oil came out like coffee then you did a "double flush" makes me think there could be dislodged debris restricting the oil pickup but hard to say.

 

[Doubeleive]

Just as crappy as when you get to empty and fill up with alternate gas? Not saying they reset forsure, but I don't think it would be any worse?

Last post about an AFM deactivator was something about them dying, and another where they couldn't pass emissions testing until they unplugged it. I feel confident in saying, it's the less preferred option.

there is a specific amount of refueling that triggers a relearn (might be alcohol content only?) I think it is 12 gallons or more @swathdiver has that memorized somewhere

 

[mikez71]

Right, my thinking is, if the alchohol content value was cleared with a battery reset, that it would attempt a relearn afterwards.. So content may show "0" but it would be in relearn mode.

If you had to replace a fuel pump, drain 5 gallons out, refill with 5 gallons of alternate fuel, the ECM wouldn't attempt a relearn? It would also need to store fuel capacity to non volatile memory, and with that would be assuming you did not change fuel type after servicing..

Just seems easier and better to let it reset?

 

[Marky Dissod]

Right, my thinking is, if the alchohol content value was cleared with a battery reset, that it would attempt a relearn afterwards.
So content may show "0" but it would be in relearn mode.

If you had to replace a fuel pump, drain 5 gallons out, refill with 5 gallons of alternate fuel, the ECM wouldn't attempt a relearn?
It would also need to store fuel capacity to non volatile memory, and with that would be assuming you did not change fuel type after servicing.

Just seems easier and better to let it reset?

PCM does not need to store fuel capacity per se, it need only note an increase in fuel pump sender voltage corresponding to a minimum 3-gallon increase.
If it does not notice a fuel level increase - say you drain out the gasoline and replace with the exact same amount of 'cornyline' -
then it'd be forced to notice a stubborn O2 sensor trend, although this could throw a trouble code,
because the pcm has no reason to expect the alcohol percentage to change without a fuel level increase.

 

[mikez71]

But we're talking about disconnecting battery, so 3 gallon increase over what?
ECM would need to save that number. Short of saving that info, it might as well relearn.?
Which is what I'm saying, it's better to relearn after battery is unplugged.
Whether GM thought so or not, is another matter..

 

[Marky Dissod]

There are certain values saved even if the battery gets disconnected. Don't know if fuel level is one of those values.

 

[Fless]

there is a specific amount of refueling that triggers a relearn (might be alcohol content only?) I think it is 12 gallons or more @swathdiver has that memorized somewhere

I feel like a broken record. 3 gallons. Excerpt from the 2008 Owner's Manual:

 

[Doubeleive]

I feel like a broken record. 3 gallons. Excerpt from the 2008 Owner's Manual:

View attachment 484334

ya i was just guessing, I thought it was more than that for some reason

 

[swathdiver]

The system recalculates the alcohol content even after a refueling event; often times days later.