Where are you and this Tahoe located? You anywhere near Philly? If you are I would offer you a hand. That way I can then communicate what I find to the guys here if we needed further assistance.
We here are basically only as good as your problem description. If a mechanic were relaying his findings then everyones responses would be much more accurate. But at this pace you are going nowhere FAST my man.
Where you located?
Blackbird
I’m from Birmingham al…
Can spark plugs just go bad? My car was running. I parked it. I removed and cleaned the intake manifold and replaced the gasket. I put it all back together. Correctly. I did arc the alternator wire accidentally. But the engine still cranks so I don’t think it will be a voltage issue. I’ve used half a can of starting fluid trying to get it. I checked a spark plug for spark and it’s there. I might check the others. Maybe replace the others? But they’re obviously ok because the car was running 48 hours ago.
I’ve checked all fuses. But again, I don’t think its voltage because engine cranks and sounds like it wants to turn over but doesn’t…
Could my starter wiring be bad? Can I hook a jump cable from starter to battery to see what that does?
But if I have spark on spark plugs doesn’t that mean starter is ok?
I am so lost
“Could my starter wiring be bad?”
No . . . because “engine cranks”
“But if I have spark on spark plugs doesn’t that mean starter is ok?”
“I am so lost”
Considering the engine cranks over and you have spark . . . I wouldn’t worry about the plugs or starter at this time. Your problem lies elsewhere, in my opinion
Did you check ALL of the fuses and fusible links . . . including the various megafuses and the interior fuse box?
Since you didn’t specifically mention checking all of the fuses and fusible links . . . as I already asked you to check . . . I will assume you did NOT check that stuff
Do you even have a multimeter . . . or at the very least, a test light?
Don’t take this the wrong way, but I think you need to tow this truck to a shop to get diagnosed and repaired properly
At least get it running . . . and then think long and hard about the “improvements” that were done before you even bought it
I put that into parentheses because you seem to think they’re improvements, while many other people would disagree
With all the cranking you are doing - if you are not smelling a lot of raw gas smell, then you are not getting fuel into the cylinders. I think the arc at the alternator may have killed your computer or some component that controls the fuel injection system.
You might have spark but the spark has to be timed properly and that is controlled by the car’s computer.
The “lost” feeling comes from being in over your head. This problem seems beyond your knowledge and available tools to make a diagnosis.
I finally got it. But I have to have the gas pedal all the way down and cranking for like 10 seconds.
It’s smoking like crazy. Especially when revved. And my throttle body is full of oil again. And my manifold is probably too
Do you have a friend who is knowledgeable enough to help??
I suspect that what may be happening is that the compression/combustion is pushing pressure into the crankcase and blowing oil up through the channels through which oil normally drains back down after lubricating the rocker arms etc. and it’s flooding the galleys in the heads and being drawn into the throttle body via the PCV valve. That means you have a severe path from the combustion chamber(s) to the crankcase, like a blown piston. The smoke is probably a combination of oil burning in volume and coolant being drawn into a cylinder via a blown headgasket.
You need to get this looked at by someone who understands how it all goes together. Brace yourself for bad news. We’ll hope for good news.
The oil in the throttle body was probably my main concern from the get-go about this truck and I agree with the same mountainbike.
If the truck were mine the first step would be to run a compression test before spending any more money on parts and wrestling with a figuratively speaking greasy pig.
The compression test results (both dry and wet tests) should provide a feeling about step two; which could be the bad news mountainbike refers to.
You obviously have some skill and knowledge or you wouldn’t have removed the manifold. At this point you are in over your head.
Most chain type parts stores (Like AutoZone or O’Reilly’s) have tool “rental” programs where you can borrow or rent tools like a compression tester. A compression test should be your next step. My guess is that you will find at least one cylinder with low (or no) compression. If you’ve never done one before, watch this: https://www.youtube.com/watch?v=X_tbksFYhl4. Please post the results here.
“You obviously have some skill and knowledge or you wouldn’t have removed the manifold”
But no common sense, otherwise they wouldn’t have bought the truck in the first place
That is my opinion
If somebody doesn’t like it . . . 
Db, the poor guy’s stressed out enough. I don’t know that it was necessary to verbalize that opinion. When faced with a choice of compassion or complete accuracy, I prefer compassion.
Do me a Flavor…and I know it seems odd. PULL YOUR DIPSTICK…and check the oil. What is the level? Is it ABOVE the full line? If you were located near me…we would already know whats wrong with this vehicle. Im sorry I cannot be there to help otherwise I would be there in a Jiffy.
Blackbird.
I agree this needs to go to a competent mechanic ASAP! I work on computers and get so many in that have been DESTROYED by attempted DIY repairs. The sad part is many of these would have been $50 fixes prior to the butchering. The problem is this SUV sounds like it has already been butchered. At least take it to the mechanic to find out all what is wrong but be prepared to part it out and scrap the rest.
I agree with cwatkin in thinking you may be in over your head at this point and also think this truck had some serious issues when you took possession of it.
Like butchered computers as mentioned, I’ve seen a fair number of cars that were either butchered or had a ton of money spent needlessly on them over the most insignificant cause.
One of them involved 3 tows (4 counting the one to me) and several grand in repair charges when the cause of the problem all along was a 25 cent fuse.
Yes, this needs to be in competent hands. I try to follow my own advice and call a pro at whatever needs doing when I am in over my head. The only time I attempt a DIY repair on something I don’t understand is when I know the repair would cost more than the unit and I have nothing to lose. Sometimes I win and sometimes I don’t but it would have been trashed/recycled anyway. Unless you are willing to scrap this one, take it elsewhere.