I had a new battery installed on my 4.7 yesterday as it just crapped out on the road and wouldn't start up at all... My wife was driving it actually but she didn't notice any overheating or anything at that point. When changing battery, coolant was gone, mechanic apparently thought I'm an idiot for letting it run without any so filled it up. After the battery swap I noticed the truck running different and it had a weird noise which turned out to be a knock. The weirdest thing was a bad, bad shake starting at around 50mph but sometimes even 35mph, that would shake the whole truck back and forth, but disappears as soon as I release accelerator. Then it overheated out of the blue, I stopped pretty much immediately. Cooled it down a little, checked the coolant- of course gone. Filled it up with water, was bubbling like mad and spitting back, thought alright..the gaskets gotta be screwed... But noticed the water gushing out from one of the hoses, was completely lose, tightened it up..- all good, water stays in, no more bubbling. Been good since apart from the knock which comes from somewhere on the passenger side in the engine bay, somewhere in the back...terrible vibration at idle and still the same crap - shaking, while pressing the gas anywhere above 35mph, but NOT always, shaking is also intermittent. But like I said goes away the same instant I release the gas. pressing down hard on gas makes the truck sound so loud I would have to yell to be able to talk in the cab and I can smell exhaust. A lot actually. Oil seems fine. Its like at idle it sounds like the timing is all weird, too slow? But rpms are the same as they always were - round 600.
I knew I had a small exhaust leak, which has sent a bunch of sensors out of whack, but could it be a bad leak now? But would it cause the bad shake? Its a rhythmic knock, goes up and down with revs.The exhaust sounds like s...t now since yesterday there's no rumble, just a tinny, knocky crap, a bit of white smoke coming out, but not a lot at all. The oil seemed fine, though. And the coolant hasn't gone anywhere either, if anything it looks kinda milky..(it is actually water) ..not sure if I could smell fumes in it or not though. There's no more overheating..keeps checking oil, it's fine..
I am prepared for the worst. But it's like 3 diff problems put together, that came together all at the same time...unlikely! :/

 

Oh and honestly, I haven't noticed a difference in performance. If there was one, then it would be negligible.

 

Anyone?.....

 

I think the first things I would do is check the overall integrity of the engine systems.

Cooling system, pressure check, make absolutely sure it is tight---the 4.7 is known for head gaskets going bad and cracked heads if over heated----at all!

Do a compression check

Check for DTC's

Dump the power by disconnecting the battery again, make sure you give the computer time to fully reboot when you turn the ignition to "on" without actually starting right away---wait a couple of minutes

Ypu obviously got something going on, but more info is needed, plus the year of the truck will help too

You could simply have a broken valve spring or a split intake or just a bad intake gasket.

Hope this gets you headed in the right direction---just way more info for everyone to help.

 

My truck is a 2003 4.7 v8, got 149k on it, but it has a 2006 engine in it. (converted from a v6)...
The only error codes now are the same I had before...p0138, p0147..o2 sensors...were meaning to fix 'em...the truck has had plugs, coils replaced about 3k mi back...a tune up basically..
What other info would you need? I will try to have a compression check done in a few days. At this point I am trying to decide whether it's worth dumping any more money in it...

 

My main question I suppose is -- what could be the worst symptoms I could possibly get with a cracked manifold or somesuch?

 

I also noticed it eats a boatloads of gas. It's got worse. Even idling for like less than 10 minutes moves the gauge down a little. It started to smell like gas now too a compression check will be done hopefully tomorrow. It sucks with it being the only vehicle to get to and from work...

Also, it's all stupid speculation, but I don't think it's got anything to do with the exhaust anymore... It's too rhythmic a tick- with a clock like precision for it to be exhaust. An exhaust would go haywire whenever you press gas, would probably sound more like the always described "marbles in a can"...But then why do I smell so much exhaust and gas in the cab?
And oil is still perfectly fine...so is coolant.

 

Alright, got compression test done. 7 cylinders at 120psi, 1 at 100psi with a burnt spark plug. Changed that and the coil.
I am thinking a burnt exhaust valve? Makes sense. Can explain the gas smell and just how much the truck eats now. Also the misfire, which should be the cause of jerking/shaking at higher speeds/rpms. Also loss of power. And the farty exhaust sound. It sounds like a damn 2.2l joke. What about the tick, though?
Does this (burnt valve) sound like an expensive problem?

 

Or a bad lifter more likely?... I read that changing just one is not really a way to go since they're all matched from the factory?

 

Bad mileage goes hand-in-hand with the bad O2 sensors.

I wouldn't say bad valves if it holds pressure. Bad milage, shakes, back fire... these can happen with bad O2 sensors and a rich condition.

Depending on the loudness of the tick, it's almost normal on the 4.7. Mine has always had a tick. But given that the truck could have overheated before when it was out of coolant, it's game for anything.