3RZ Burnt Valves

1995 Taco 3RZ W59

Hey guys! Been a while since I posted anything and I just wanted to give a quick update to anyone who may have miss fire, rough idle, and low power issues.

My truck at times would have trouble starting, miss fire cyl 2/3, low power, and when sitting idle I could tell the engine had excessive vibration judging by how much my stick shift would rattle.

Finally after about a month of issues I decided to get deep into it and see what it could be. I did the basic checks and the most important one I did was the compression check. I highly recommend checking that as one of the first 3 things you do.

Turns out I had like 50 and 60 psi on cyl 2/3.

I pulled the head off and immediately could see the issue just by looking at the valves.

This is Cyl 3 exhaust valve compared to Cyl 4. Look how much smaller it is (burned).





I had an extra head laying around that I already soda blasted and purchased new valves/head bolts/ head gasket set/etc...

Went ahead bought some lapping compound and got to work.



After this I went ahead and started to measure all of the bucket shims I had from 2 heads and started working on trying to get everything to spec. Unfortunately, this did not work as the tolerances were too tight in areas and too large in others for the different size shims to compensate. Some shims after measuring that I would need Toyota didnt even make.






After this set back I turned to my local machine shop. I knew a guy that worked there so I went over and he tested my lapping job first. Well I was almost there as there was a 20% leakage. Sigh* Well that was a good 5 hours wasted but it was a great learning experience nonetheless. I got them to go ahead and trim the valves themselves to fit the shims and cut new seats. A box of doughnuts made sure it was all done within 2 hours LOL

Here is the final result.









All in all it was a great learning experience. The truck now purrs with no issues. The stickshift barely vibrates. No more missfires. No more hard starts. More power. Better fuel economy.

Compression test is very important guys I'm sure most of you know. If you have missfire codes definitely look at your spark plugs followed up by a compression test.

If you made it this far thanks for reading!

 

Nice write up, good to see your fix went in the right direction.

 

The 3RZ motors are known to burnt up exhaust valves. The valve lash decreases and the exhaust valve no longer closes all the way allowing for some blow by during the combustion process and ends up burning up the valve. This is at least how I understand the reasoning why these engines burn up valves. This is why it's imperative to do regular valve clearance checks and adjustments with the 3RZ motor.

https://www.youtube.com/embed/f0zzsBhs3iA

 

@Russianman92 good to see you on here again! I doubt you remember but very first post on here was about rebuilding my trans and you helped me out alot

I was unaware of this until @0xDEADBEEF had a similar burnt valve issue but our inline 4 motors have a tendency to tighten up the valves as it get older and they should be checked and adjusted every 50-80k

That is a gorgeous looking valve job there

 

yup I am aware. This was a used motor I put in with good compression and I did do a valve adjustment when I put it in. I suspect a leaking manifold was the culprit until I upgraded to mini headers.

 

Glad I was able to help! And thank you! Yea I was excited to put that head in after seeing how beautiful it was haha.

 

Thank you for all the information, this is great! Out of curiosity, could you help me understand how a leaky manifold affects your valves? I had a cracked exhaust manifold for a while…

 

It won't cause the valve to burn but it will lean up the mixture as fresh air might get sucked in through the crack leaning out that cylinder and forcing the ECU to richen all of them. Bad MPG to follow.

 

Truth.

 

A most excellent write up!