When to rebuild engine?

[Trip_84]

I am curious as to when it is optimal time to have an engine rebuild done or maybe it is case by case? I currently have 240k miles on my V6. I've always had the complaint that the 4runner just feels tired and weak. Riding trails going over the smallest obstacles like rocks or little lips I have to floor it and just feel like I barely make it over. Even going up a curb feels like work. Going in sand I'm flooring it just to stay barely moving while I see other 4runners and jeeps moving really good through the same terrain.

Not sure if its a compression issue or something else. Does anyone recommend a good shop in Las Vegas or southern Utah to get work like that done?

 

[JZiggy]

Start with a compression check. Low compression means there's a mechanical issue robbing you of power (worn rings, valves not seating, etc.)

 

[Pilotmatt]

I know ill be dropping in a v8 when my engine goes…just 20-30 years to go!

 

[Devbot]

Are you running ethanol free? Personally I notice a night and day difference between even 10% and 0%, ethanol free feels immediate but 10-15% is noticeably sluggish
Otherwise, to directly answer the question, when it breaks and can't be repaired!

 

[spartacus]

When was the timing belt done? A worn, stretched timing belt will have that effect also.

 

[Devbot]

^^^And take a peak at your harmonic balancer while you're at it. I remember seeing a while back the keyway can become wallowed out with age

 

[alumarine]

Notice how no one has said "time to rebuid".

Lots of things to check for poor performance that don't include rebuilding.

 

[Trip_84]

Notice how no one has said "time to rebuid".

Lots of things to check for poor performance that don't include rebuilding.

hmm that seems to be more of a broad statement though. I also titled the post "WHEN to rebuild?".... no one seemed to answer that. Yes I have my own issues but I also would like to know WHEN someone would rebuild an engine. When it becomes cost effective? When is that? Something specific happens or breaks?

 

[Trip_84]

Start with a compression check. Low compression means there's a mechanical issue robbing you of power (worn rings, valves not seating, etc.)

I just finished doing the compression test. I followed the Timmy The Toolman's video. He states the book says 174PSI minimum and no more than 15PSI difference.

I attached 2 plugs. The dirtier of the 2 is the 115PSI plug and the cleaner one is the 191PSI.

 

[lord rigatoni]

I just finished doing the compression test. I followed the Timmy The Toolman's video. He states the book says 174PSI minimum and no more than 15PSI difference.

I attached 2 plugs. The dirtier of the 2 is the 115PSI plug and the cleaner one is the 191PSI.

jeez man no wonder your 4runner feels sluggish, thats some serious compression loss. id check your valve seats and your valves to see if any of them are burnt. your piston rings could also be fried as well so yeah it may be time for a rebuild. if you have the tools you could do it yourself, rebuilding engines can be a good time.

 

[19963.4lsr5]

It’s worth checking your valve adjustment.


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[Brian.]

... but I also would like to know WHEN someone would rebuild an engine. When it becomes cost effective? When is that? Something specific happens or breaks?

Used 5vz engines are about $500 around me, about 4~5 times Cheaper than rebuilding and they are VERY robust engines. So rebuilding isn't really Ever a viable option.

But rebuild/replace when there's an Obvious deficiency within the engine... burned hole in piston, broken rings, spun main bearing type issues. Otherwise pull and replace is a Whole lot faster and cheaper. Might invest some time in the replacement engine to make sure it's all "fresh" before putting it in place... maybe.

 

[2chains]

Aren't the spark plugs double tipped for 3rd gen?

 

[Devbot]

I just finished doing the compression test. I followed the Timmy The Toolman's video. He states the book says 174PSI minimum and no more than 15PSI difference.

I attached 2 plugs. The dirtier of the 2 is the 115PSI plug and the cleaner one is the 191PSI.

Well there's ya problem! :target:

Used 5vz engines are about $500 around me, about 4~5 times Cheaper than rebuilding and they are VERY robust engines. So rebuilding isn't really Ever a viable option.

But rebuild/replace when there's an Obvious deficiency within the engine... burned hole in piston, broken rings, spun main bearing type issues. Otherwise pull and replace is a Whole lot faster and cheaper. Might invest some time in the replacement engine to make sure it's all "fresh" before putting it in place... maybe.

If I'm not mistaken you can get them fairly fresh in a crate from Japan for like $1500 (just the price of the engine, not shipping and whatnot too). Or if you wanna spend some dollars Yota1 will give you one that's brand spanking new with some nice powdercoating
All things considered our engines are pretty affordable. Could be much, much worse

 

[Bad Luck]

Aren't the spark plugs double tipped for 3rd gen?

Double ground spark plugs are recommended for the 3.4L. It helps from getting worn out due to the waste spark ignition system.

 

[diverscale]

You've got so much to go through before rebuilding the engine. This is the final of many steps of finding why you ''lack power''.

Could be simple as a bad maf or o2 sensor.

 

[Trip_84]

You've got so much to go through before rebuilding the engine. This is the final of many steps of finding why you ''lack power''.

Could be simple as a bad maf or o2 sensor.

But did you see the pics I posted? Its so hard to know who to listen to. You're saying that but I've had people on here say the complete opposite (look at the responses since my compression test pictures). And 2 people I've spoke to in person today suggested a rebuild. Why would an o2 sensor cause compression 65PSI below Toyotas minimum on multiple plugs?

 

[gamefreakgc]

But did you see the pics I posted? Its so hard to know who to listen to. You're saying that but I've had people on here say the complete opposite (look at the responses since my compression test pictures). And 2 people I've spoke to in person today suggested a rebuild. Why would an o2 sensor cause compression 65PSI below Toyotas minimum on multiple plugs?

Not everyone reads the whole thread.

I also second a valve adjustment. I would not pay a shop to do it though as many of them will charge enormous labor costs because it's a complete pain to do. I've done it 3 times and it takes a lot of patience. You may also have one or more cracked valves, which in that case no amount of adjustment and shim swapping will get the lost compression back. Unfortunately the only way to find a cracked valve is to pull the cylinder heads off as even a leakdown pressure test won't tell you whether the valve is out of adjustment or if it is cracked..

Your bottom end most likely is rock solid but the valve in the heads need some R&R to get that power back online. I drove for 4 years with one cylinder at around 90 PSI, but 3 cylinders is a bit much.

P.S. my engine blew up, that's when I knew it was time to replace it lol!

 

[TravThePro]

If your heart is really set on doing a rebuild, listening to the people who talk of valve lash is going to be the most helpful advice.

I would recommend buying an angled feeler gauge to check what clearance you're running before you go and make that decision. It would be something like this ZUZUAN 1 Pack Feeler Gauge with 32-Blade and 1 Pack Offset Feeler Gauge with 16-Blade, Gauge Dual Marked Metric and Imperial Gap Measuring Tool: Amazon.com: Industrial & Scientific

Another good thing would be to buy a cheap borescope that will connect to your smartphone to check what all of the cylinder walls/pistons look like.

Keep in mind that doing these above jobs to test an engine with good compression from a junkyard is going to be significantly more economical than rebuilding your 5VZ. It is also very easy to mess up things like the rod cap bolts (these HAVE to be replaced if you loosen or take them off else the engine will explode).

Best of luck

 

[Bad Luck]

I would recommend a leak down test on your cylinders with low compression. Adjusting valve lash isn't going to help if the problem is worn piston rings.