AdmiralYoda

I've been trying to wrap my head around this since I put my 87 4Runner w/22RE back on the road after it sat for 15 years. The motor originally came out of an 85 and it has about 125k miles on it.

I've driven it for about 8,000 miles now and have noticed 3 things:
1. It consumes about 1-1.25 quarts of oil every 1,000 miles.
2. The oil turns Ink-Black after about 750 miles of use.
3. There seems to be excessive blow-by. When I remove the oil cap while the engine is running, there is alot of air coming out of the cap.

I've replaced the PCV valve and verified it is functional and has suction. I did a compression test and all the cylinders were around 170. There are absolutely no oil leaks and the engine runs great with plenty of power. I consistently get about 24mpg. I drive 27 miles each way to work, all highway....so it gets some good exercise everyday.

There is also NO smoke on startup and no visible smoke while it is running. It is obvious that it is burning the oil because the tail-pipe is sooty.

Any ideas? My first thought was blow-by due to worn rings but my compression numbers are good! I'd appreciate your help!

kcaudill

Might be leaking valves

AdmiralYoda

Wouldn't I see smoke during start up then? Even if it sits for a week....no smoke. No visible smoke behind me when I'm driving either. At least none that I can see using the mirrors....

JasonYota

iTrader: (1)

Have someone drive behind you to look for smoke, it could be smoking but you can't see it from the rear view mirrors.
Have you done wet and dry compression tests? Odd that the compression is that high with blow by coming from the oil cap.

AdmiralYoda

The compression test I did was dry. I was expecting to see a dead cylinder honestly. Plugs had only 5,000 on them but looked pristine. I was expecting at least one of them to look nasty. Weird!

One thing I haven't checked is if the hose going from the intake to the middle of the valve cover has vacuum on it. Air is coming out of the port on the valve cover, but I don't think I checked to see if the hose had suction. I'll take a look during lunch.

AdmiralYoda

Well that was disappointing...I was hoping for something simple. Took the PCV valve out and there is definitely suction on the valve. There is also positive pressure coming out of the PCV valve hole, so the internal baffle isn't clogged.

I unplugged the vacuum line that goes to the middle of the valve cover too. It has some suction on the vacuum line though not as much as I'd expect for the size of the line. There was positive pressure coming out of the valve cover hole as well.

gandude

I have the same issue with my 3.0 V6 truck.

I think the oil is not draining fast enough from the top end. The oil gets sucked into the PCV valve.

Possible reasons;
High volume oil pump.
blocked passages back to the oil pan.

Try condensing the vapor output of PCV valve into a coffee can or similar.

ditypup

Might be time to install an oil catch can. http://oilcatchcan.com/

AdmiralYoda

Okay....that might explain why I'm losing oil, but it wouldn't really explain why its turning black so quick!

ditypup

Well actually, if your intake is already gooey with a black oily mess like mine was, that stuff is going back into the intake and into the combustion chambers and some of it gets past the rings into the crankcase and contaminates the clean oil. Also you say a lot of air coming out of oil cap, sounds like pressure leaking past the valve guides maybe. I wonder if the valve seals are leaking?

ditypup

Could it also be a case of running too rich? is there some black soot around the tailpipe? I remember when the AAP on my carb'ed 85 was leaking it was burning rich and that is very black output. Since the exhaust gases get returned to the plenum then that could be contributing to the problem.

AdmiralYoda

The tailpipe is pretty sooty but I'm not sure if its from fuel or oil. It runs great and gets 24mpg so it doesn't sound like its running rich.

I come from the old school chevy crowd....and leaking valve seals mean smoke on startup right? I've got no smoke.....ever.

gandude

If the path back to the oil pan is restricted, it would be from gunk. This gunk would mix with fresh oil perhaps turning it black sooner than you are use to.

Oil consuption would be my worry, not the color of the oil.

ditypup

Well, my 22RE was using a quart of oil in a couple hundred miles and it didn't smoke at all that I could detect on level ground. Now on steep inclines and declines it smoked. I never did figure out why. Didn't smoke in the morning. I guess it is a tribute to how powerful the igniter is. So, I wouldn't go by if it is smoking or not 100%. I could however smell the oil in the exhaust. Kind of a sick sweet smell. If you got black soot at the tail pipe I'd say its running rich.

ditypup

Oil getting blackened to me would indicate carbon deposits in the oil. And that would come from the combustion process.

wyoming9

iTrader: (1)

An Engine sitting for that long is going to have these issues Just change your oil more often .

It may clean up it might not.

If your getting blow by into the valve cover it will contaminate the oil with the unburned hydrocarbons.

Could be both issues helping to darken the oil

RSR

Try Amsoil engine cleaner.

Uses detergents rather than solvents...

http://www.amsoil.com/shop/by-produc...mission-flush/

Probably wouldn't also hurt to run a very thin 5w30 or so, full synthetic long life oil with a lot of detergents in it as well after the amsoil flush to try and clean everything else out.

And the amsoil can be used at every oil change as well...

gte718p

I would run a can or two of seafoam through the oil. Most of the save you engine additives are junk. I didn't really have high expectations for sea foam, but my machinist a ASE master mechanic with 40+ years swears by the stuff. Its basically alcohol and detergent.
Throw a can in the oil and run it hard for a week or two and change the oil.
Carefully suck a can through the brake booster vacuum hose. It will clean out the top end. Be careful not to suck to much or you can hydrolock the engine. You'll be amazed at how much crap if frees up. Huge clouds of smoke come out the tail pipe from all the excess oil/crap being burned.

RSR

Seafoam is a solvent. It dissolves engine gaskets in addition to gunk...

That's why detergents rule. The Amsoil is anything but junk.

RSR

Seafoam is still one of the better upper cylinder cleaners, but for everything else it lists that it can do, you're better off with newer technology...