I have a bit over 275k Miles on the ole 5VZ-FE. The engine runs like a top. Seems to be to have very good power. I change engine oil every 3,000-3,500 miles and in that time I have to add no oil and if I pull the stick after 3,000 miles it will still be at the top mark on the stick. Uses zero coolant.

I wanted to check the spark plugs so I did that today, I used to have a compression tester but had lost it so I ran to harbor freight before checking the plugs today and bought a 20$ compression tester because I wanted to check it while I had the plugs out.

To do the test I did the following:

-Removed coil packs
-Removed all 6 spark plugs
-Removed EFI 15A fuse from fusebox.
-Did test with engine hot and throttle wide open.

Following the engine cylinder sequence the compression numbers were as follows:

Cylinder 1: 130psi
Cylinder 2: 115psi
Cylinder 3: 125psi
Cylinder 4: 125psi
Cylinder 5: 130psi
Cylinder 6: 120psi

From what I have found it should be somewhere between 175-200psi and that Toyota says 145psi is the minimum. With the difference between any cylinder no greater than 15 psi.

The biggest difference between my best cylinder and worst is 15psi.

Maybe this cheap gauge I bought is just reading low? On other engines I have tested I am used to seeing around 180 or so.

How can my 3.4 have such low compression but use no oil/coolant and runs great. I was going to check the valve clearance soon, maybe I need to move this up to an ASAP deal to rule out any tight valves.

I was planning on running this thing for A LONG time and by the way it runs I would say I can, but by those numbers I say I can't.

It does turn over a bit more before starting and that has always bugged me compared to my Honda Civic which would start by barely bumping the key, only difference was the darn Honda burned a quart of oil every 2,500 miles, the 5VZ-FE burns none. Scratch head.

 

With any high mileage engine, you will never have compression at spec as the engine is worn. Worn piston rings, plugs, coil pack, ignition coil, ect.. can cause low compression. If its running fine and your not burning oil or coolant, I would not worry too much.

 

Yeah I am not going to loose any sleep over it, that is for sure. Like you said, if it was consuming oil pretty good then it would be different. If it ever comes down to it, I will put in a rebuilt 5VZ-FE. The truck is worth it.

Also I didn't really expect to see the compression way up high with this many miles, that was just a wishful hope of mine. I just figured if it was down where mine is, that oil consumption would be an issue but it looks like you need to dip lower than that for it to be an issue.

 

Harbor Freight compression tester reading low? Just a thought...

 

That's kind of what I am thinking. I am not going to worry about it really. I will continue to take care of it like I always have.

I would say either the tester is reading wrong(low) or, an engine can get to that PSI and still be good enough not to burn oil, etc.

 

I haven't driven any other 3.4 Toyota engines, so I have nothing else to compare it to, but my truck takes way longer to start than any of my old, beat up 4 cylinders. It cranks 5-6 times before firing. My 1978 Toyota pickup usually fired on the first or second crank.

Not sure if it's just the nature of these engines, or if I need to do a little ignition work. I have new sparks plugs and wires in a box but I'm planning on doing the valve cover gaskets once it warms up so at this point I'm waiting until that job to do the plugs and wires. I'll be interested to see if that helps. Usually the first thing I do with a "new" truck is replace plugs, wires, distributer cap and rotor but, well...this truck doesn't even have some of those things! New engine experience for me...

 

It might very well be the nature of the 5VZ-FE as far as starting. I put about 55 miles on the engine today, ran like a top just like always. I am also use to the Distributor cap, rotor, etc. I am actually glad the 5VZ-FE has the ignition it does. There is a lot of 92-95 5th Gen honda civics in my Family. They are known for the coil to go bad and leave you on the side of the road. Carrying tools and a spare coil was normal for me just in cast. Atleast with the 3.4 if you look a coil I guess you loose 2 cylinders, would not be fun but atleast you might could limp her home.

 

You plugs, coil packs, etc. can not cause low compression. This is simply how well your rings and valves are sealing. Just needed to clarify this bit of misinformation.

I wouldn't worry one bit about it either. If it runs good- run it.

Your longer crank times could be FPR leaking down a bit. You'll have to get a banjo bolt adapter kit (or rent from AZ) to test your fuel pressure after the truck's been turned off for a while. Check your running pressure and see if it drops considerably after it's been turned off for a while.

 

I had not thought about a leaky FPR. If it bleeding off pressure back while sitting, your right, it would take longer to start. I will see about checking the psi, then at least I know, its not a big deal to me overall, just always thought it was weird it took longer than other vehicles I have owned to start.