Cylinder compression at 6,000 ft

My 2006 Tacoma 4.0L with 210k miles on it has the following compression readings taken at 6,000 ft elevation near Denver: 135,134,136,137,139,140.

The average is 137, variance from lowest to highest is 4.5%

Google gave me several websites that say to divide the reading by .836 to convert from 6,000 ft reading to sea-level adjusted value of 164 psi.

Is 164 psi a "good" compression for a 2006 with 210K miles on it?

 

Toyota says 189 psi is standard
145 psi is minimum
And 15 psi difference between cylinders.

You look to be in the middle of your math is correct
With 210k, I’d say you are ok…Again, if the math is correct?

 

FSM states 145PSI minimum, are you having an issue with misfires or oil burning?

 

Well if the altitude adjustment is correct (and multiple websites say it is) then I am at 164 and minimum is 145 so should be good to go!
No misfiring, just a chronic feeling of being underpowered. Especially uphill. For example, to go uphill on the freeway and maintain 75 mph, it tends to drop down a gear. Now, this is at 6000-7000 ft in Colorado, so that is certainly a factor.
It's a much-neglected Taco and I'm doing a full tune-up to try and improve its power. I wanted to check compression to rule out major problems.

I am doing: New plugs, clean MAF sensor, clean throttle assembly, cleaning injectors (with fuel additives), new air filter, new PCV valve.
I am considering: New ignition coils, remove and fully cleaning injectors

 

Trying to keep 75 going uphill at that elevation it's gona downshift, if you have no misfires or oil consumption I would think engine mechanical is fine.

I wouldn't change the coils, cleaning injectors may not hurt but it's not very common for them to give trouble.
Are you running stock tires? Oversize tires will also make the truck feel like it has less power.

 

No misfires, no oil. Just feels underpowered.

 

It has a 3" lift and wheels upgraded from 16's to 17's. I bought it this way.

 

5psi variance. And at 6k ft you are looking at around 20% thinner so your numbers are fantastic. Your motor is doing danged good. Keep up consistent oil n filter changes / standard maintenance and she will keep chugging along.

 

What size & type of tires are on it?

 

What size and load range tires?
The 4.0 isn't a powerhouse to begin with, any extra weight or larger tires you add is gona make it feel more sluggish.
Without driving it I couldn't tell you for sure if the performance your getting is normal or not, if you knew someone with a similar truck I'd say drive it and see how it compares.

 

LT 285/70 R17

 

I'm 1000 meters and we see 140-150 often on older tired engines. I'd say over 140 is fine for colorado.

 

OP, did you just get this truck recently (saw your other spark plug thread)? If so, and you have little-to-no seat time under your belt with this truck or a similar Tacoma to use as a baseline reference, then I'd say everything sounds about normal to me.

 

No I've had it for about 5 years but have not done anything except change the oil. It's always felt underpowered. I was going to sell it but have decided to keep it. Now that I'm keeping it, I want it running well.
I'm doing some other work on it too. It rides very rough. The tires are terrible, "LT"-type, more suited for off-road which I don't do, and worn unevenly. I'm putting new tires on it, plus shocks all around, and front springs. Hoping this will get it riding a bit smoother. It sounds like nothing is wrong with it, but the tune-up (plugs, MAF, injectors, filters) is long-overdue anyway.

 

Stock tire sizes depending on trim level were 245/75 R16, 265/70 R16, and 265/65 R17 so your running an oversize and heavier tire on top of being at high elevation.
Again without personally driving it no one is gona be able to tell you if it feels normal or not, your best bet would be to drive a similarly equipped Tacoma and see if it drives nearly the same as yours.

Calculator to see how tire sizes compare.
https://www.tacomaworld.com/tirecalc

 

75 mph uphill at 6,000 ft with LT 285s and you're wondering about downshifting? Your truck is fine. In fact, if you slowed down to 65 I'll bet your mpgs would improve.

 

You lose 3% engine power for every 1000' elevation. At 6000' most engines are only putting out 82% of the power they would at sea level. Turbocharged engines like the Ford EcoBoost engines aren't affected as much.

I live in GA and normally drive at altitudes of 500-3000'. When I've visited western states the power loss above 5000' can be dramatic. If the engine has plenty of power to spare it isn't as bad. My Tacoma is actually better than a lot of vehicles I've driven at altitude. Your tires are the real culprit. You'll be underpowered at sea level.

 

Thank you all for your input. Glad to hear the engine is fine and it's just my expectations were a little unrealistic!!