The 1FZ-FE motor requires the valve clearances to be checked. Unlike earlier motors on the Land Cruiser series, the valves do not get louder when they wear. The clearances will shrink due to wear on the shims and the valves will get quieter. Checking the valve clearances is about an 2 hour job and one will need some gaskets and seals. Adjusting the valves are a different matter since the shims have to be removed and replaced or swapped to obtain the right clearances. Checking valve clearances should be done with the motor cold.
We wanted to share the following with our readers. We recently opened up a 93 1FZ-FE motor to check the valve clearances. When we removed the valve cover we found the plastic timing chain 'slipper' had broken in two and the broken piece was pushed up all the way on the guide. The timing chain tensioner pushes this guide against the chain to keep the correct tension on the chain. The tensioner is hydraulically operated.
With the slipper out of position, the chain was running on the metal guide. Not a good thing. The part had to be replaced. The new part shows some improvements on the old design. Why the part broke, we have no idea, but close inspection of the break showed that it was cracked for some time but broke recently. Removing the slipper and guide turned out to be a big job. Toyota calls for pulling the head and both oil pans to remove the front timing chain cover.