Timing chain jumped. Why?

[MIKEINSJC]

I had the 22r engine in my 86 4wd rebuilt about 15,000 miles ago. I used a local shop, as I have heard too much negative stuff about "mail-order" engines.

I drive my truck like an old man. Heck, I am an old man. I was tooling through town the other day and lost power. Limped the truck to my local mecahnic who discovered the timing chain had jumped two teeth. He reset it, and said the tensioners appeared to be working fine. Any ideas what may have caused this? I have not been to the shop who did the rebuild yet, as I wanted to get some input from this forum first.

[jetwhine]

Mike in San Jose Ca.,

There are a few things that should have been checked.
1) There is a wear limit on the tensioner which measures approx. (.0433 in.) If worn below limit it needs to be replaced.
2) There are wear limts on the dampers which is approx. (0.020 in.) Same thing if it is worn then they would need to be replaced.
3) If the tensioner is leaking oil bad and is bypassing oil then it might not have enough oil pressure to operate properly and would cause slack on the chain which will allow it to possibly skip teeth.

I would say that any one of these things could cause the chain to skip. This would be my take on the issue. You would though have to remove the timing chain cover to asses the issue.

I almost forgot, A badly worn chain could also cause the skip problem.

[fourwd1]

It will jump because there is too much play in it. Either because the tensioner isn't doing it's job, the guides have disintegrated, or it's so worn it has stretched. None of which would normally occur if it was replaced with an engine rebuild 15K ago. The tensioner and guides are replaced along with the chain and gears, it's a complete kit.

[Zembonez]

"Resetting" a timing chain is NOT a fix. Once it jumps time it is either stretched or the guides / tensioner are gone.

[DCM]

What sort of rebuild was it? Do you have a list of parts that were replaced? I'd check to see if the complete timing set was replaced - chain, guides, tensioner and sprockets. All these should have been replaced new, as a kit.
The plastic guides themselves do not tension the chain, they merely hold the chain from slapping against the inside of the timing cover. The tension is applied by a spring loaded and is assisted by oil-pressure once the engine is running.

[verlaryder]

Rebuilt Toyota engines are never as bulletproof as factory original Toyota engines because American rebuilders are sloppy and use aftermarket parts to "rebuild" stuff.

Also, if your rebuild was needed due to engine overheating, the cyl head was probably shaved which
can cause the chain to run slightly slack.

Best to install a Made in Japan timing chain kit like the OSK brank kit you can find on ebay