tombothetominator

Hey y'all!
I think the ol' girl might have finally bit the bullet, but am looking for advice to make sure. I ramble a bit - forgive me.

The truck: '91 Toyota 4runner, 3.0 V6, 5 spd, ~315,000 miles. It's been my DD for the last nine years. There are no major issues to my knowledge, only little minor things that come up with this many miles. I've owned her for the last 180K of those miles.

The driver: 28 year old jack of all trades. I've done most of the work on the truck over the years (except clutch and timing belt), so am fairly comfortable with a wrench, but am far from being a real mechanic. For the most part I assume automobiles operate on magical pixie dust until I actually see how the insides go together. Oh, and I'm ridiculously poor as well, so doing the ol' part swap and pray thing doesn't jive too well with my wallet.

The problem:
- Driving home and suddenly there is a ridiculously loud noise. Sounds like a giant old diesel dump truck when they really hit the gas. Noise lasted just long enough for me to realize it's coming from my engine bay (maybe 7-10 seconds) - . Then the engine dies and I start looking for places to get out of traffic.
- I try popping the clutch with the truck in gear as i coast, thinking that it might have been a fluke (hoping more than thinking really) and the truck might roll start. I get nothing though, no noise, no fire.
- I get it towed to the house and check for codes. I get a code 12 (RPM sensor), and a code 75 (EGR valve, which I've been getting for three or four years now).
- I see that code 12 often has to do with distributor, so I check for spark at the dizzy, and get none! I read the forums and see that a common check is to bump the starter and see if the distributor turns with it to see if it is bad. The dizzie doesn't turn!
- I pull the distributor out, expecting to see some torn up teeth, but the gear is intact, and it spins freely once removed from the truck (while on the truck I cannot turn it).
- Next I think - timing belt snapped (after 30K?!?!). So I pull the timing cover off, but the belt is intact as well. It doesn't look like it jumped timing a tooth (crank at 0* mark, all the lines on the camshaft pulleys line up.
- So now I'm stuck. I can rotate the crank just fine, and all the timing belt pulley's turn fine, but somewhere between the cam pulley and the distributor something is broken.
I've not ever gone under the plenum, so I'm not sure what is really under there besides more 'automotive magic pixie dust'. I assume the timing belt turns the cam which determines valve positioning(?) and also turns the distributor gear? So maybe the cam went fubar, or a valve got bent to hell somehow, causing the cam to not turn properly?

So that's where I stand. Any ideas, oh worldly (and good looking, no doubt) mechanics of the toyota-sphere? Thanks, and have a rad afternoon!

Co_94_PU

iTrader: (-1)

http://personal.utulsa.edu/~nathan-b...68cylinder.pdf

Not sure the fastest least destructive way to get a look in there. maybe magnetic pickup tool thru the dizzy hole and see if you can fish anything out.

EG2-50 (in the fsm) shows your LH cam, looks to be a big enough bearing surface it could of snaped and not droped the cam sprocket.

cman1

iTrader: (1)

make sure you cant spin the timing gear on the dizzy shaft,pin might be sheared.

MudHippy

The problem is more than likely with the distributor itself(as in the shaft is probably snapped). I'd be willing to bet that a more thorough inspection of the the distributor would reveal this to be the case.

EDIT: cman1 beat me to it...

RE-EDIT: Pretty sure that's not what I was talking about. FYI, the timing gear is integral to the shaft on these distributors(as in not removable/there's no pin to shear).

tombothetominator

Thanks for the replies guys!
CO_94 - I'll see if I can roust up a magnet on a stick and see if any shrapnel comes out.

CMan, and MudHippy - if the pin had sheared (if there is one) or if the shaft itself ad snapped (if there isn't a pin), wouldn't I be able to spin the dizzie rotor when it is mated to the cam gear? It is held fast when I put the distributor in the engine, but when I pull it out it spins freely. I'll take a closer look tomorrow in the daylight.

JonnyBoy

Sounds like the cam is somehow locked up. You can turn the crankshaft by hand, right? The driver side valve cover should be possible to remove without removing the plenum, if I remember right. I think I'd pull that off and see what it looks like inside there.

Co_94_PU

iTrader: (-1)

For the distributor, give it a good twisting pushing pulling inspection. For the cam it's not very deep, a good flashlight and someone to hand crank the motor and I assume you'll be able to see deep enough to get eyes on the cam sprocket. Not sure about the valve cover, book doesn't get to removing that until step 35 or something

And after poking around a bit I see that cam pully doesn't have a ground keyway just the pin in the pulley. If this sheared you'd get your symptoms, no idea oon the root cause other than the cam siezed.

JonnyBoy

Yeah, I'm mostly thinking the pin sheared off. Co has a point, you probably could do it with a flashlight.

scope103

The drivers side (left) valve cover can be removed with the plenum still in place. It's a fiddly operation, so I wouldn't do it as a practice, but if you have a good reason ....

Here, you should be able to see plenty through the distributor mounting hole. Be gently turning the crankshaft by hand; if you have loose parts/debris inside the valve space you want to minimize additional damage.

tombothetominator

Thanks again guys for the info! I did a better inspection of the action in the distributor and it definitely seems to be operating properly. Also - with a flashlight down the dizzie hole I can indeed see the cam gear, and it does not turn with the crank - so it looks like the connection between cam and pulley sheared.

From what I've been reading it seems like the most likely reason for cam failure is lack of lubrication, perhaps a plugged journal or something along those lines (I don't really know what a journal is, but am parroting my latest research info), is that correct in y'all's estimation? And having the cam seize in the middle of operation has probably caused other damage on the valve assemblies and/or scoring of the head, correct? To say nothing of whatever shrapnel is probably sitting in the oil from the cam's demise.

SOOO... does anybody know of a source for factory-spec camshafts for this engine? I looked around all the online parts stores I know of, and found plenty for the 22-re, but none for the 3vz. AAAANND - beyond replacing the camshaft itself, I'm assuming I would most likely be in for a head re-surfacing to clean up any damaged areas? Plus replacement of any valve assemblies that may have been damaged, and replacement of valve cover gasket/head gasket. And a few oil changes in the near future. Anything else that I might be missing?

What other causes are there for camshaft failure? I'm assuming if it was something like a piston trying to escape to the outside world, turning the crank would be next to impossible and would make some nasty noises? I might try to take of the valve cover without removing the plenum this weekend when I have a day off.

It's looking like the runner may be going to wherever good trucks go when they die. I choose to believe that there is a car heaven where the streets are lined with premium fuel pumps, synthetic oil change shops, and mud pits for the trucks to play in. It's a nicer thought than rotting in some u-pick-it lot.

Dras16

Take that motor out. Do a SAS, and then throw in a chevy 350! Dont just throw it away! I know you said you are broke, park it for now and just do little things as the money comes in!

scope103

If I recall correctly, the distributor gear is machined into the cam; you can't have the cam turning without the gear turning, unless you've broken the cam all the way through. And I find that pretty hard to believe.

But the cam is driven by the cam sprocket by a 5mm pin called a "knock pin." If the cam bolt got loose enough for there to be some wiggle, the knock pin could have sheared, and the cam sprocket turns without the cam turning.

We're all just guessing here, but it is possible that all you'll need is a new cam sprocket and knock pin. Maybe. So it sounds like you need to at least remove the valve cover, and the top of the front case, to see what's going on when you gently turn the crank.

MudHippy

I like that idea...for now.

cman1

iTrader: (1)

yeah,its a pull stuff off and search mission now!

tombothetominator

Well the valve cover came off today. And look what I found:


A little closer look:


And a view from the backside:


And the two pieces of shrapnel I could find:


It looks to me like the 'adjusting shim' shattered, then the cam jammed the 'lifter' towards the center of the head, and and eventually jammed itself up against one of the broken pieces, which caused the shear pin to break between it and the pulley.


Thanks everybody for helping me get to the bottom of the problem! You all rock!

scope103

"Knock pin." I don't make up the names.

Thanks for the report.

MudHippy

Wow! We certainly don't see that every day...that's for sure. Or ever...that I'm aware of.

It looks to me like the lifter must have jammed first, then the cam shattered the adjustment shim, and eventually pushed a broken piece of it into a position where it jammed itself up against it(and the already jammed lifter and/or head), causing the knock pin to shear between it and the pulley.

Why that scenario? Because I can't imagine the adjustment shim being shattered by the cam lobe, unless the lifter were already unable to be pushed downward by it. Those shims are some EXTREMELY tough little cookies(made of VERY hard steel).

My question is...what caused the lifter to jam like that?

JonnyBoy

Wow is right. Never heard of that one happening. Interesting to note(to me anyway) the cam has been removed from the head, maybe for the hg recall, but probably something else. I spy the chrome bolt head of a (probably) larger bolt in the upper right of your first picture there.

tombothetominator

Scope - sorry, you are correct.

MudHippy - that could very well be the case. I'm not going to tear it apart any further to see what the rest of that valve assembly looks like, but looking at the FSM diagram maybe the spring retainer broke, causing an uneven load on the lifter?

Johnny-Boy - The block was replaced at 110K due to headgasket leak, so that may be why the chromie is there.

Thanks again everybody!