3vze Timing Belt Walking off Cam Sprocket.

Hi folks,
I have a 95 4 runner 3vze that I recently bought, in non running condition. I removed the timing cover and saw a few things: the cam sprockets were oriented differently than I have ever seen. The right (passenger side) sprocket was turned with the lip facing out, and the left was turned with the lip facing in towards the head. The belt had walked towards the timing cover and actually walked up over the lip on the right Cam Sprocket. This allowed the cam to jump a few teeth.

The belt and components were aftermarket, gates, that had been installed I believe by the previous owner. I removed the belt, tensioner, tensioner idler, center idler/water neck, and Cam sprockets. I left the water pump because it seemed to be in good condition.

I turned the cam gears around so the right is lip facing in, and the left is lip facing out (this is the only way I've seen them), replaced the tensioner and idlers, installed the belt (timing marks all spot on) and when I rotated it around 2-3 times by hand, the belt began to walk about 1/8 in. Off of the right Cam Sprocket. At this point the belt is beginning to rub on the fan bracket. I did not start the engine, I stopped when I saw that, as I knew it wasn't right.

I did some research on another forum and found a thread where someone had the same problem. Someone pointed out that he may have installed the belt backwards. He stated that he turned the belt around and the problem resolved.

So I went back to look at mine, and sure enough, I had installed the belt in the same orientation as the poster in the thread... "Backwards".

I turned the belt around, RE-assembled everything, turned out over a few times by hand and it tracked straight and did not walk like before. I then started it and found I had dead misfires on #5 and #6 (separate problem). This new problem required me to pull the cylinder heads (burnt valves) and when I removed the timing cover I saw something I didn't expect... The timing belt was walking off the right Cam Sprocket! I'm at a loss now and I really don't know what is causing this. Could the tensioner idler be misaligned or something?

 

If the upper idler pulley bearing is worn or improperly manufactured it could cause the belt to walk off the cam pulley.
I would suggest installing an AISIN TKT-014 timing belt kit. All of the components in the kit are from OEM vendors. I would also install a new OEM or AISIN thermostat since you get a new water pump with the kit.

 

Ok, I will try that next. I'll give an update when I have the heads back on and install the new kit. I was a little suspicious of the machining on the import direct upper idler. Thanks for the info

 

Update:

Had the heads rebuilt and installed with new Toyota head gaskets.

Installed Aisin Tkt-014 timing kit. And new Toyota tensioner pivot bolt and washer.

Set engine up on time, installed fan bracket and hydraulic tensioner. De-pinned tensioner and rotated the engine over by hand 5-6 rotations. Just as before, the timing belt starts to walk off the cam gears and begins to rub on the fan bracket.

I'm starting to get angry.

Is there a spec for how far the end of the crankshaft gear is to be from the face of the block?

There doesn't seem to be any major crankshaft endplay, but maybe the crank gear is not seated all the way back? Or wrong? Or installed wrong??

Also, I did install the washer that goes on after the crank gear and installed the harmonic balancer before roasting the engine over.

 

Check the runout on both cam gears, maybe one or both are bent. Put a dial indicator on the front face, the runout should be very close to zero.

 

Final update:

Checked the runout on both cam gears. Very close to 0. Found there was a problem with the tensioner pulley arm, causing the pulley angle to be off.

Went with an OEM tensioner from Toyota and now it tracks straight.... Go figure. $192 later, just for the tensioner pulley.

Fired it up and the thing runs decent, hits on all 6. Still have some tuning to do, but if the transmission's 100% I should be on the road (or off the road) soon