Timing chain replacement on a Toyota 4-cylinder?

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so looks like I have a good amount of slack on this timing chain. I haven’t read chain replacement being a fact of life with Toyota 4-cylinders outside of the 18/20/22Rs. I don’t hear a death rattle at startup - the only time I hear chain rattle is on WOT on-ramp runs or uphill occasionally. Has anyone had to replace a timing chain on a Toyota?

I consulted with @The Critic and we think the chance of the engine jumping time is good - I’ll drive the car as gingerly as possible until I can get the replacement done. My plan of attack - new OE chain and rails, the tensioner is in serviceable shape and it’s a simple hydro mechanical part actuated by oil pressure. The sprockets don’t look like they developed shark fin wear. I’m leery of the procedure to retime the engine. I’ll seal the cover with Toyota 103 FIPG or Permatex Right Stuff 90-minute Gray and fill the cooling system with Prestone Cor-Guard.

One thing I’m toying with - a intake cam swap. Someone on PriusChat said the intake cam off a Echo/Scion xA/xB/xD is a bolt-on power adder - the Prius cam has a long duration and closes late, while the Scion is a “normal” cam with shorter duration and closes at the end of the intake stroke. The Prius cam keeps the intake valves open into the compression stroke - Atkinson cycle.
 

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TCL

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You may have a hydraulic tensioner and the slack may be caused by it not being pumped up to take the slack out since it's not running.
 
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You may have a hydraulic tensioner and the slack may be caused by it not being pumped up to take the slack out since it's not running.
I have never seen a healthy one cause this much slack when the vehicle is off. Not even one that was bone dry inside.

This should get the OP started on the repair:

Capture.JPG
 
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Which engine? My old Corolla had an external tensioner that was easy to replace.
 
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If I tore into the engine that far, I'd be replacing everything that was reasonably priced. I would definitely change the tensioner with a loose chain. I know it really shouldn't be bad, but if there was a 5% chance it could be not working correctly I'd replace it.
 
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I've done quite a few 1GR-FE timing chains to correct timing error DTC's, They were all neglected though. Other than that.....I'd say modern Toyotas rarely have Timing Chain wear issues, But I'm not very familiar with 1NZ engines.

I looked at service information, Timing the engine looks to be very straight forward, They even have you back the pistons off TDC to eliminate the possibility of valve to piston contact. Uses colored links....EASY!!
 
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I’m not sure I would change the intake cam. You will certainly lose some fuel economy, which is counter to the mission of the Prius. more than that, however, I’d be concerned with how a change in output would be seen by the computer in its balancing act of mg1 and mg2.
 

nthach

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I’m not sure I would change the intake cam. You will certainly lose some fuel economy, which is counter to the mission of the Prius. more than that, however, I’d be concerned with how a change in output would be seen by the computer in its balancing act of mg1 and mg2.
Yea, I was looking at the parts breakdown between the 1NZ-FE and FXE, the pistons and rings are different. If I wanted to go that route, I’d buy a 1NZ-FE from Pick & Pull and do a DIY refresh - new rings, gaskets, valve seals, timing parts.
 

nthach

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They even have you back the pistons off TDC to eliminate the possibility of valve to piston contact. Uses colored links....EASY!!
That’s what threw me off - the steps to get the crank at 40-130* ATDC and then lining up the colored links to to the timing marks on the cam/crank sprockets.

I recall doing a timing belt on a 3MZ-FE and it reminded me of that - but the marks are IMO a little more succinct with a belt.
 
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It's the same concept, You're just not directly on TDC. The Crank is 50°, The 2 Cams are 25°......With all 3 colored links lined up with the sprocket timing marks.....It's IN TIME.

I have arguments with seasoned mechanics over Ford 3V Modular Timing jobs.....I set the crank off TDC & use the colored links in the chains to time the engine. Service information has you remove certain rocker arms/followers to do the job at TDC.
 
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