The knock might be confirming your fears... but I thought all Toyota engines were non-interference with the valves? Anyway, unfortunately your suspicions could be correct though. If a piston is in fact hitting a valve, then the reason the belt is skipping is (probably) because the valve is momentarily being held firm by the piston. The crankshaft keeps turning but the camshaft sticks from the bent valve, so the valve train gives at the point of least resistance, the timing belt.

It's also possible the retainers on one valve might have popped loose, or that a valve spring is broken. I'd remove the valve cover and have somebody crank the engine over while i watched the valves. If valve-to-piston contact is happening, at least one valve isn't going to open like the others do and it'll probably be evident. And if a valve is bashing a piston that would explain the TB jumping time, but, you might be able to fix it by doing a valve job. Since it runs, you know there isn't a hole in a piston, yet... you will see what shape the piston top is if you get the cylinder head off. And if the valve contact is minor enough the valve job might be enough without changing the piston. Might be worth a try, anyway.

You might be lucky and have it not be the piston-hit-valve problem, if so, though, first thing is, of course, check the obvious. Examine your timing belt, I mean remove it and look for a crack on a tooth that isn't obvious. Next thing check all the gears involved. One of them could have a broken tooth.

(By the way, I just listened to your youtube audio, is this engine still making that banging noise a year later? My friend, I'd get a used japan engine or something. This one is probably going to need a lot of money, parts and machining to make it right.)

 

but I thought all Toyota engines were non-interference with the valves?

Not even close....

 

belt keeps jumping 1 tooth for every 2 full 360 revolutions @ Cylinder No.1 TDC.All the marks line up; crank pulley, cover marks, cam marks all line up. But, still every 2 revs, it jumps 1 tooth. So if i turn engine 4x, its 2 teeth. It continues. So by the 6th x, it's 4 teeth.

That's normal if you've marked a tooth and expect it to align by the same tooth on the pulley. As you said cam, crank, cover line up, that's all you need for correct timing. Go by those not the belt.

Knocking separate issue.

 

Did you put the belt on backwards?

 

I realize my timing is off, but I can't understand why my belt keeps jumping 1 tooth for every 2 full 360 revolutions @ Cylinder No.1 TDC. Before the above incident, new timing belt job was done. So tensioner, belt, idler pulley, water pump are all new. All the marks line up; crank pulley, cover marks, cam marks all line up. But, still every 2 revs, it jumps 1 tooth. So if i turn engine 4x, its 2 teeth. It continues. So by the 6th x, it's 4 teeth. I'm able to start it, but it's got that loud knock. Sounds like valve to piston contact in the above link.
I may have bent valves. Even if that's the case, I'm not comprehending how that causes timing belt to skip since the gears are still turning. I've tried using 2 diff tensioners w/ same results.
The other thing is if I'm adjusting the distributor to correct timing, it sounds a bit better if I'm turning it to the right towards the firewall. Right now, I'm all the way to the right. It's louder if I turn it to the left.
If my belt stops skipping i think i'm in good business.

Please feed me some knowledge!!

The reason the timing belt marks don't line up is that the timing marks are not symmetrical.


I'm not sure about your engine specs, but on a IMZ 6-cyl there are 211 teeth in the timing belt. From the bottom center mark, where the printing is, there are 75 teeth on the left side, and 77 on the right side, and 59 teeth between the top two marks.


It sounds like your timing belt is the same as the IMZ because as you have noticed that every time you rotate the engine the marks are 2 teeth off, which is the difference between the 75 teeth on the left side compared to the 77 teeth on the left side of the center mark on the timing belt. It would take some 105 revolutions until the marks all lined up again due to the asymmetry of the marks on the timing belt.


The 4-cyl motors, however, are different. The marks *will* line up after each revolution if the timing belt is installed properly.


But this has nothing to do with the knock you have.


That needs some more investigation.

.

 

Thanks for all the replies!! i just ripped this engine apart 2x, so I'm trying to do the least amount of work before i do it 3x. I was really hoping or felt optimistic that it was timing and timing(no pun intended) will fix all since I noticed a bit of difference when I realized the timing was off.
The torque converter seizing really messed things up then. I knew it threw the cams off(i had to reclock the camshafts), made the belt skip and timing was way off.
RobertMaybeth - thanks for the suggestion, but i'm not going to notice anything before oil flies all over the place and the cams will be spinning too fast. I just tried this on another car and it didn't work out so well.
Maybe i can rotate the cams manually after the belt is off and feel if there's any resistance in the valve train.
I had to say this, but I don't want to spend another 1-2k on this car. I do all the work myself, so cost is for parts only. At this point, I really think it's a bent valve, but before I take off the head, I may do a leakdown test on each cylinder. I'll remove the intake mani and check the RH cams to make sure they're aligned. I've already used a stethoscope and its the loudest in the LH right in front of the exhaust mani. I hear a bit noise in RH, but can't tell if it's resonating from the front or not.

BlackCamSe - no i did not. I just did a timing belt job before this while replacing both headgaskets. Ran like a champ and passed Cali smog w/ flying colors. Passing smog is the hardest thing to do around here.

ajkalian - i don't know, but according to the manual, it's supposed to line up after every 2 rev. Also, they lined up the same way after 2 revs when I did my 1st timing belt job. Everything was perfect as per the manual.

 

Just to clarify, the timing marks we're supposed to verify are the metal markings on the cam sprocket and backing plate, and the easiest on the crankshaft is to have the lower cover and balancer installed so it's right on 0 TDC?

The white paint marks on the belts are primarily for V6 because it's such a pain to have to remove the hydraulic tensioner and redo. On the 4-cyl, most brands of belts don't have paint marks, maybe the Toyota one does. The cheap 4-cyl manual tensioning system wasted people a lot of time. Not sure these paint marks line up every 2 revs. But the metal markings should.

If it's off by a tooth or two then either the belt was too loose on the radiator side at install, or the tension wasn't right and it skipped later. You can try loosening the tensioner, then lift up the belt a little at the cam sprocket and just turn the *cam sproket* back one or two teeth. It might help with the spark plugs removed so the belt doesn't try to skip as much.

 

If it's off by a tooth or two then either the belt was too loose on the radiator side at install, or the tension wasn't right and it skipped later. You can try loosening the tensioner, then lift up the belt a little at the cam sprocket and just turn the *cam sproket* back one or two teeth. It might help with the spark plugs removed so the belt doesn't try to skip as much.

I think i know what you mean. Are you stating for me to compensate the tooth that will be skipped by turning the sprocket back? I tried that and it keeps skipping consistently the more I turn the crank. So I did assume it will skip 1 tooth, so i went back 1 tooth. But it'll just keep skipping. I don't believe the belt is loose, or at least it's not visible or feel-able. I've tried loosening the tensioner and played around w/ it. On top of that, it's new, so the pin is within speck and has plenty of force. So far, regardless of what I do, it will skip.

 

The marks on the belt are just for the initial install. What matters is the alignment of the marks on the cam and crank.

The V6 belt install is simpler than the I4 because of the marks on the belt. I listened to your video and the belt install is fine. My friend, your problem is deeper in the engine and a lot more expensive.

 

some quick updates. I'll try to keep frequent updates as time allows and also I like to put put some closure on my threads if I can.

I double checked all the timing marks(not the belt) again and they all seem to line up. Marks on the crank pulley, timing covers, cam sprocket marks w/ the back cover as well as the cam gears themselves(the 2 dots aligning both cam gears together). I proceed to rip everything apart. I have the head removed and I do not see any obvious signs of bent valves. I will remove the valves tonight or tomorrow for further investigation.
Part of me is thinking this is something easy and stupid and I ripped out the head for nothing.

I still don't get this quote by Robert; The crankshaft keeps turning but the camshaft sticks from the bent valve, so the valve train gives at the point of least resistance, the timing belt. The cam sprockets are bolted to the cam shelf and aligned via a pin. If the camshaft sticks, so would the sprocket. As mentioned, the sprocket aligns w/ the timing marks on the cover every time. Which still doesn't explain why the belt teeth would skip. But, lets skip this (no pun intended..lol) and concentrate on the valve train.

I hope it's a broken valve spring or something. Makes my life easier at this point. More updates to come.

 

I have the head removed and I do not see any obvious signs of bent valves. I will remove the valves tonight or tomorrow for further investigation.

Not sure if you did a compression test. Valves can be checked two ways. Shine a bright light up the ports in the dark and any non-seating valve will show light. Or, pour gasoline into the ports and see if it runs out. Properly seated valves will not leak. It will be hard to see slight bent if valve removed.

 

Also, leaking valve seat does not necessarily mean bent. Seats wear and they can have crud on them. You would need to use valve grinding/lapping compound and suction cup tool to spin the valves and clean the seats up, then check. Not expensive from Amazon for kit.

I recently did this on another vehicle (no bent suspicions) and just kept lapping until no light came through.

Make sure you keep the valves in order of cylinder they came out of. An egg carton is useful. You'll need to check valve guides and replace seals before assembly. Also need to have head flat checked - don't use feeler gauge as it is unreliable.

 

Thanks. Something i came across while searching awhile back was someone stating to put the valve in a cordless drill and turning it. That was what i was going to do.

 

You don't want to damage the valve stem in the drill chuck. The grinding compound is only meant to lapp the seat with the valve. Using the hand method turns the valve CW and CCW for a better seat. It takes some time and patience so I would not use a drill. As well you need to keep applying the compound to the seat as it gets pushed out by the spinning.

 

If the head is still off the car you can rotate the cam and look at both sides to see where it's sticking. The crank should turn very smoothly with little effort with the timing belt removed.

 

Just check your valve lash to see if you bent a valve. If its bent you will have a BIG gap between the cam and the follower.

Sorry you got perplexed on the timing belt. Belt position doesnt matter as you found out, timing marks lining up do matter! If you want some fun try timing an OHC ford V8! They use marks on the chain and those marks do NOT line up with each revolution. Took me a while to figure out a method that works.

-SP

 

thanks for the reminders and great tips.

JohnGD - Would I be able to tell if I have a spun bearing by spinning the crank? The head is off and I installed the cams back on and turned the cam pulley to see if I see anything obvious. i don't. I'm beginning to think for the worse; spun bearings

speedy - I was perplexed by the belt because of the skipped teeth or what I thought was teeth skipping. And I thought the sound related. From information I gathered earlier, the sound was caused by a badly timed motor or bent valves. So i was stuck on that. After i set timing and the sound still persisted, I thought it was bent valves.
But now, contemplating some more, I don't feel like it's bent valves? Even if the valves were slightly bent, a properly timed non interference motor wouldn't cause valves to hit the top of the piston or interfere. Continuing from above, my new thinking is that; in order for the piston to contact valves, it would have to be mistimed, or the bearings are spun to the point the piston goes higher than it's supposed to, which = contact to valves.

Guess i'm moving on to removing the oil pan. From what others have said, i probably should've started here...=/

Coincidentally, this scenario just happened to another car of mine. a '92 sentra, w/ 300k miles. Same noise. This time, i took it to redline and the sound happened shortly after...lol.

 

@Wusta515, I would love to work with you on this. If you don't mind someone learning from you and hopefully figuring out things with you, just tell me where to turn up and I will be there. I am in San Diego.

I have done many of these timing belt, seal and wp jobs the last few weeks to save up some money for my own, so I know how to turn a wrench.

I want to learn how to rebuild these engines and transmissions.

 

Thanks! Not sure what to say, but nice surprise and thanks for the kind gesture. However, I'm a very busy person. I work on this car sporadically, so I don't really have a set time. If you looked at my other thread, it's been almost a year before I finally started again..lol. I work 9 hr days and I don't get home until about 6pm. Then, I try to exercise. If i feel good after dinner, I put an hr or 2 in and go to bed. Then on weekends, I relax and usually just hang out w/ my family and vege out =) So I don't really have a set date where it's even worthwhile for you to come up and help me. The best I can do is update this thread and let you know what I find. Also, the worst case for me at this point if everything goes to hell is for me to donate it.

 

PMed u - iluvmy98

 

Does anyone know what the piston clearance is between the piston at tdc and the top of the block? I can't seem to find that in the fsm.
So I found cyl 4 & 6 piston sits higher at tdc vs piston 2. Which explains y it's hitting the valves. When at tdc, 4&6 piston sits flush to the top of the block while 2 is lower @ .135" below the surface of the block.

 

So I found cyl 4 & 6 piston sits higher at tdc vs piston 2. Which explains y it's hitting the valves. .

What the

I wonder why that is. 1MZ is non-interference as you know. At this point I'd drop in another engine or sell the car

 

Updates. I took the oil pan out and there's flat pieces of metal. It didn't feel or look like metal. Looks more like hard plastic. I used mgnet and sure enough, it's metal. I also measured the stroke. That's what I was asking about earlier. Stock is 80mm and you can see the walls on the cylinder where the piston stops before going back down. Cyl 4 is about 81.3mm and cyl 6 is 82, while cyl 2 is good at 80. People increase stroke, but n this case when everything's stock, its bad.. ha!
I couldn't see any obvious signs from the bottom, but something's def putting that end of the crank higher. Everything looks attached and no gaps. I'm going to assume it's the main bearings. But if it's the bearings how did my stroke increase? If I lost thickness, shouldn't it decrease? Unless something got wedged in there?
Next is, can I take out the bearing cap while rods, tranny and obviously motor still in place? I'd like to check to see if it is the main caps or thrust washers. Yes I know I should replace the whole motor..etc. but I still like to know the answer to this if I can. And if I can, replace the bearings and get her moving! Save a life!

 

What if the loss of a bearing or two gave the rods enough leeway to stretch?

I was just troubleshooting something like this on a 5S-FE in another thread, but my rods were hosed. Bearings fused to them and everything.

 

Thanks for everyone's response. I'd like to formally provide closure to this thread. Per the last few post, I've determined and narrowed down that it's the main bearings or perhaps even thrust washers. Because of the damage caused, it's not something I can simply replace while the engine is in the car. We're trying one last effort to see if some family members will want to get a new engine for about $1k. If not, then it's done. I'd still like to know what is actually happening. I live for this kind of stuff and have a high interest, but the circumstances leave me no other choice. :frown:

Good bye 93 camry..................................:crying: