Strange start after battery died during oil change, video included

[Dustin Jackson]

Yesterday I went to change the oil and realized I had the wrong oil filter so I left the Tahoe sitting overnight with no oil in it, no oil filter installed, and the hood cracked open (not full open just resting on the latch).

Today I got the right oil filter installed (filled with oil), filled the Tahoe with 6qts of oil and went to start it. Usually I hold the gas pedal to the floor and cycle the starter for a while to try and prime the oil system. The battery died on me after just a few cranks which was strange.

So I rolled the Tahoe back so I could get my pickup in place to jump start it, I got the jumper cables hooked up and attempted to hold the gas pedal to the floor and cycle the starter like I usually do but this time the motor fired up instantly at full throttle resulting in some terrible sounds. My TPMS light is off so it seems the battery died enough to reset the computer.

My questions are why did it do this?
Does the gas pedal to the floor mode not work when the battery is dead or when there are jumper cables applied?
Would the hood being popped caused the battery to drain over night?
And what was that terrible sound in the video?

Tahoe starts around 30 seconds

 

[iamdub]

Totally flying leap guesses:

My questions are why did it do this?

The throttle blade was in the WOT position when the system lost power and maybe it had fuel in it for some reason and that was a couple of backfires?

Does the gas pedal to the floor mode not work when the battery is dead or when there are jumper cables applied?

The PCM was reset and didn't know the TB was in the WOT position and allowed it to fire. I don't see how the jumper cables would have anything to do with it. All they do is transfer battery voltage.

Would the hood being popped caused the battery to drain over night?

I don't see how. GM omitted the hood light and, even still, it'd be controlled by the BCM and shut off after X mins.

And what was that terrible sound in the video?

Hopefully fuel in the exhaust igniting and nothing mechanical directly related to the oil being "extra" drained.

 

[Dustin Jackson]

@iamdub Very interesting about the battery, I only got about 1 crank cycle out of it before it got too weak to turn the motor anymore. I’ll get it tested.

Another thought is that when the computer is reset it might have been trying to use A/F ratios for gasoline but it’s full of E85 causing it to cold start.

Should I be concerned or just keep driving until something breaks?

 

[iamdub]

@iamdub Very interesting about the battery, I only got about 1 crank cycle out of it before it got too weak to turn the motor anymore. I’ll get it tested.

Another thought is that when the computer is reset it might have been trying to use A/F ratios for gasoline but it’s full of E85 causing it to cold start.

Should I be concerned or just keep driving until something breaks?

If it's doing fine now, let it go. If there is anything, it's probably nothing you'd ever find unless you removed and disassembled the engine and maybe even Magnafluxed parts.

I'm betting it was a backfire and nothing mechanical. There's nothing draining the oil would've caused. The internals still have oil in/on them as if it was parked overnight, over a week, two weeks, etc. regardless of the pan being empty. These things are tough and run on the verge of detonating, relying on the knock sensors detecting minor detonation to tell it to back off the timing. Mine broke a spring and bent a valve. Actually, this was a year ago today. I buffed out the piston, swapped the valve (with a used one from a junk a head) and replaced all the springs. After a short break-in, I took it to ~135+ MPH then immediately started road tripping it, including 2,000 miles to Tampa, Florida and back. Even that drive included a few blasts well in excess of 100 MPH and ~6,300 RPM shifts.

 

[donjetman]

Maybe?
Leaky injector(s) partially filling a cylinder(s) with fuel so it hydraulic locked when you first tried to start it. Then when you jumped it it did what it did.

 

[iamdub]

Maybe?
Leaky injector(s) partially filling a cylinder(s) with fuel so it hydraulic locked when you first tried to start it. Then when you jumped it it did what it did.

 

[Dustin Jackson]

That’s a good theory but it’s trumped by the fact the battery ran low enough to reset the computer I think the reason it didn’t start was a dead battery not hydrolocking.

Tomorrow I’ll try to replicate the situation before I go to work, it would be strange to think I’ve been driving around for months with only enough battery for 1 engine start attempt

 

[iamdub]

That’s a good theory but it’s trumped by the fact the battery ran low enough to reset the computer I think the reason it didn’t start was a dead battery not hydrolocking.

Tomorrow I’ll try to replicate the situation before I go to work, it would be strange to think I’ve been driving around for months with only enough battery for 1 engine start attempt

I wouldn't dismiss that theory. Have your battery tested. It might be strong enough to crank the engine in your everyday normal situation but too weak to overcome a partially hydrolocked engine. The starter cranking the engine is the largest draw it sees. With the engine locked and the starter trying to turn it, that current draw multiplies as it's almost the equivalent of a dead short and that would drop the voltage down to be deader than dead. Your PCM wasn't 100% "reset" as it didn't have to relearn idle, etc. If a combination of our theories are half-assed correct, then it's like the sudden voltage drain confused some of the "short-term memory" aspects but the base maps, etc. stored in "long-term memory" were unaffected.

 

[Dustin Jackson]

I had the battery tested and they said everything looked good but the battery “needs to be charged a little bit”. Which is what they said last time I had the battery tested about a year ago so not sure what to do about that. My commute is 20 minutes five days a week so that should be giving it plenty time to charge.

When I got home I attempted to replicate the problem by turning the motor with the gas pedal to the floor and it turned for a long time and didn’t stop so I wasn’t able to reproduce the problem today. I will try again another day after it’s had a chance to sit for a while.

I’ll keep my jumper cables in the Tahoe in the meantime. I suspect the battery might be on its way out and I hope that explains this situation.

 

[avalonandl]

Change battery, these vehcles need full voltage.