1992 1UZ jumps timing

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Peacebay

New Member
Messages
2
Hello guys,

New to this board but not new to working on uz series engines. Just picked up a real clean 92 LS400 for cheap because it wouldn’t start. Previous owner insisted that the engine must have jumped time again because it had done the same thing to him twice in the 100k miles he owned the car.

Tore the engine apart and sure enough, the RH cam was off a tooth. What was more interesting was that the tensioner pulley showed signs of having seized briefly at one point but now spins freely with no play. It honestly feels like new pulleys I’ve installed. All parts installed by PO were oem.. NTK bearings, Toyota belt.

No oil leaks from cams nor coolant leaks that I can see. Belt was bone dry. what would cause this??

Attached are some photos. Lextreme wouldn’t let me upload full size images unfortunately. Thanks in advance for the help!
 

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gloverman

Well-Known Member
Messages
2,968
Location
Hamilton. New Zealand
Thats really interesting. Last one I had with timing out was exploded ignition rotor under the belt. With your one did it have the washer under the back of the tensioner bearing unit? How was belt tension when you pulled it apart? Is the hydraulic tensioner soft at all? Cheers
 

Peacebay

New Member
Messages
2
The belt tension seemed fine and yes, the washer was behind the tensioner assembly.

The tensioner was really tight, too tight to compress with just my hands.

I talked to the lead tech at my local Lexus dealership and he can’t figure it out either. He said to just replace with oem parts again and hope for the best. Probably my only option!
 

Red-Camaro

New Member
Messages
2
How many rpm's are being run through the engine. High rpm can cause that to happen. There is a heavy duty tensioner that is sold by an ausie company for performance application...........normal driving shouldn't be an issue. It easy to have the right side off a tooth at installation also.
 
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