How many miles do you have on this car because these engines can go for a very long time. Unless of course you dropped a valve seat. Maybe a stethoscope could help you locate the exact source of that sound.
117k miles... that's not that many right? For what it's worth I do change the oil from time to time.
you can test this car for the crankwalk by simply pulling on the crank pulley then pushing it back in. Do this a few times so you get a feel for it whether it is moving or not. You will be able to tell if this is the case. Many times the crankwalk is only the thrust bearing worn down and replacing it will fix this issue and get you many more mile out of the car.
if you did have the crankwalk as bad as you think you may have based on the sound then your car would likely not run. Another indicator of the crankwalk will be at the crank position sensor. Take this out to see if there are any signs of contact with the flywheel.
i have had to fix the crankwalk a few times. As mentioned, changing out the thrust bearing took care of it most of the time. One time required replacing the crank. That is a big job but can still be done in the car. With any luck you just have some chatter from the timing belt not being tensioned as it should be (easy fix) or one of the other pulleys chattering. fingers crossed
OK... I can get 10 thousands of axial play at the pulley, with a little pry bar to move it:
Doesn't seem like that much to me. But maybe I'm not pushing hard enough.
In any case, yes, the car chewed through the crank sensor a couple years ago. Apparently that sensor is really important. Once I figured that out, I put spacer washers under each screw when I replaced it, to keep that from happening again.
Oh, and for like 5 years, I can hear the flywheel grind against the starter, just a little bit, when the torque converter unlocks in fourth. So.. I try not to make throttle inputs that make the torque converter unlock in fourth. And at one point I had to replace the starter, I guess they don't like it when the flywheel grinds against their little gear thing. The sound has not gotten any worse, but crank walk is definitely a problem for this engine.
However, the current problem does not sound like the flywheel is grinding against something. I thought it was a bad pulley, and was really hoping so, because I had an old pulley on the timing belt that I should have replaced but didn't. So I think we can all at least agree, the problem should definitely have been that old timing belt pulley.
But nope, I put in a brand new timing belt pulley, and tensioner and belt for extra good luck, and the noise is still there.
Kinda sounds like its not getting oil up top... i dunno :/
Bummer about the engine noise, perhaps you could just ask for a no obligation estimate at a repair shop?
I'm guessing a big part of the trouble changing Fiero timing gears is due to the engine being transverse and mounted in the back of the car.
Regarding timing chains, I've had three of them go over the years on high mileage engines. Two small Ford V8s and a Cadillac. The good thing about chains is that usually, and in all my cases, they fail by jumping a tooth. So you can limp home, the engine merely runs like crap.
I took it to a mechanic shop down the street, just a block away, close enough to drive with no serpentine belt installed, to see if his professional ear could offer insights. He isn't super familiar with this engine, but said it'd be worth checking the variable valve thingy on the cam shaft, but probably I would need to take it an engine machine shop or something because it sounds like an engine problem.
Yeah... chains wear out. No argument there. But belts don't wear out, they break.