engine rumble/vibration on startup, 155K

Have you ever cleaned the EGR system?

Coolant is leaking from the tank, does it need to be topped up?

What is the condition of the engine oil?

 

You should turn it off if it rattles. You could bend a rod.
Is the coolant tank low?
It “may” just be condensation from a hot engine and cool outside air. That’s normal.

 

So if you start it and it goes to raveling what happens if you step through it almost floor the gas pedal It immediately clears up seems like it's RPM dependent when you're at whatever idle is called in this thing. It seems to bounce all around The minute you step on the gas engines running just like it's supposed to like it has been all of its life so far and then it'll do it when in drive but only when your foot's off the gas seemingly if you keep your foot on the gas matching speed or adding It doesn't do it? My persona's doing the same thing but completely different engine and everything It was fine for about I don't know 10K and then was back to the same thing that it was with the other engine at 240k close to it anyway We just gave up We need the car to be on the road not being played with in the parking lot every other day basically a money pit and other things were starting to falter door skins door panels console lid all this stuff is highly expensive or not available now it may be available on clothes out or clearance but that was no help then and now the car is deteriorated even more If I'm lucky I'll be able to use the seats and something else.

 

Moderation takes five posts iirc

 

What's also "normal" is head gasket failure, right around your miles.

I'd say something" should have been cleaned about 100k miles back, and 50K miles thereafter, but I don't want to wake the dissenters. That cleaning should nclude the intake manifold, which has "something" passages as well.

With symptoms just starting, I'd:

Boroscope inspect the combustion chambers, first thing in the morning after a good drive the previous day, looking for coolant pooling atop cylinders, exceptionally clean piston tops, and tears of coolant at the head gasket seam. Pressurizing the cooling system should accelerate formation of the latter.

If coolant is seen, I'd do the head gasket replacement, using the full Toyota gasket kit, and new head bolts. Timing chain is likely fine, and it's guides. Check the head and block for flatness against specs. Spray copious brake cleaner (it evaporates fast) into the the upside down head, to see if any of the valves leak.

If the valves leak and/or the head is out of flatness specs, you may need to enlist a machine shop. Some do that anyway, and supply them with replacement valve guide seals. All of that is in the aforementioned gasket kit.

Watch lots of videos, Gasket Masters, Sane Auto, Auto Scholar with Mr B, and so on. My signature has various relevant links. Last one is the full engine section from gen 3 Repair Manual, has spec's, torque, tons of info. (if you're viewing on a phone, turn it landscape to see signatures.

Regarding piston/ring replacement: how's the oil consumption. That said, your year does have the low-tension piston rings, and they are prone commence oil burning right around your miles, and when you've already got the head off, it might be prudent. It "is" possible to separate the upper oil pan, disconnect the piston arms from the crankshaft, and push them out. This guy's video is invaluable, recently linked in post by @rjparker. He does pull the engine, mounts it on a stand.

If and when you get the head gasket done, it's worthwhile to replace the water pump, and do a full clean of the EGR system (oops). Top two links in my signature have info on the latter.

Not sure if I've linked this in my signature; attached TSB has the gasket kit, head bolt and piston/ring part no's.

 

If the engine is running unevenly, it is necessary to check the fluid levels and their condition.
Cleaning the EGR is also necessary.
If there is no damage to the gasket, then the EGR is most likely filled with coke, soot and oil deposits.

 

Worth noting: Toyota (and the dealerships typically echo this) issued a warranty extension for "issues'. Basically says if if you get code P0401 (EGR valve sticking) or experience knock/shake on cold start, they'll fix it. My Toyota Canada version shows a cut-off of May 24th of 2018 with unlimited miles, and/or 10 years from new purchase or 240k kms (150k miles), as the end of warranty extension.

But no recommended preventative maintenance. By the time you get either of the above symptoms, you're basically having head gasket failure. Most typically it happens between 150k and 200k miles. Lower usage cars it can happen sooner. @bisco's '12 plug-in was getting shakes at 87K IIRC.

Toyota has everything sewed up neatly, at least from their point of view. Not sure any of the other companies are any different, so here we are.

 

Because of condensation…
You should still keep an eye on the coolant level though.

 

155k miles and no EGR cleaning would have me bracing for the inevitable.