Went out today on a dirt road excursion in my '87 4Runner to see the remains of our high desert snow.

My rebuilt engine with about 4,000 miles on it started blowing substantial smoke on acceleration and backfiring slightly on deceleration. Still seemed to run strong as ever.

Fuel mileage has been around 22mpg. Has used less than 1/4 quart of oil in the last 2,000 miles. Oil still honey colored-not black Castrol GTX 10-30

Got home and began troubleshooting:

Timing @ 5-6 BTDC jumpered and about 12 BTDC unjumpered== normal Plugs 1-2 and 4 light colored and normal for 4,000 miles service. # 3 sooty black and somewhat oily.

Compression test shows all 4 cylinders @ 165-170psi

Guess I'm gonna change out the fuel injectors next and see what happens. I don't have a known good one to change out #3, so I'll just get a set of 4 and change them all.

Don't know what else to do. I guess there could be some FUBAR with #3 piston rings or #3 valve seals, but this issue has developed suddenly and compression is still spot on.

Will take a few days to secure alternate injectors. Stay tuned......

 

What color smoke? If white, even after reaching op temp, prob good to check coolant levels for loss and/or contamination.

Block test seems to be another useful tool, if a possible crack in the head but below the HG...

Any codes during diag check? Might be too soon to tell...

 

Smoke gray/white on acceleration, blackish on decel. No apparent contamination, or loss of coolant.

No check engine light, but have not checked for stored codes.

Still runs strong and idles well.

My gut feeling is that a fuel injector/injectors will settle it. And a new O2 sensor just because I got a couple NTK spares cheap and the installed one is some knock-off.

Should have injectors tomorrow, or monday latest.

 

My gut says injector or non firing plug. What wires cap/rotor and plugs are you running?

 

YEC brand Japanese made cap and rotor. Genuine Toyota plug wires Denso W16EXR-U plugs.

All new with new engine 4,000 miles ago.

 

Injector is my guess then. I hate guessing on stuff.

 

Well, I been running my second gen, wheeling and camping with my friends in the cool weather of spring; so progress has been slow.

Head off and no smoking gun there. #3 was blackest, so first piston to come out. Oil ring not stuck, but practically no expansion.

#2 found similar. I'm thinking that the new NPR .50mm over rings may have been mismatched when packaged.

I put a compression ring into a cylinder before I assembled them to check, and its end clearance was right, but I didn't look closely at the oil scrapers.

They are near 1/8 inch small when held up to a compression ring.

I'm gonna do a light hone and go back with Hastings moly rings this time.

I have used NPR rings with good results many times in the past, but I'm gonna change up.

Parts ordered and cleanup/prep begins. More to come.

 

I did change injectors with no difference found.

 

You put a light on them to make sure they are firing? Or getting proper voltage?

 

Noid light strong. Engine still ran strong on all cylinders. Compression strong enough to burn excessive oil without misfire. At least for the couple hundred miles between failure and disassembly.

Just about sure that fault in oil ring fitment/tension is the trouble.

 

That "noid light strong" could give someone the wrong impression, due to the injectors always having battery applied. It's a switched ground, the ECU grounds the injector, and it has a very short duration compared to the time an incandescent bulb cools off.

...
My only other instinct aside from the rings leads to a crankcase venting issue where it could push oil past the valve seals. This is due to the blowby from ring gap/wear balancing with the PCV system.

 

I did test for excessive blowby by removing the PCV valve from its grommet and reving the engine.::: No substantial crankcase pressure evident, even with no PCV suction on the crankcase.

I know all the ordinary things that might be checked and I was stumped. Looking like the oil rings are not correct. Lots of work, but I'll know in a little while.

 

New Hastings moly rings, Cylinders honed with 220 grit stones

New King con rod bearings, Ishino-Stone graphite head gasket. (No slipper plate)

Should be running in a day, or three. Gotta set the oil pan and front diff; wiring and upper plenum.

 

Was the Ishino-Stone a complete head gasket kit? Do you have the part number?

 

Yes, a valve grind/ top end set::::

 

Rolled her out of the garage today. B+ to FP to check for fuel leaks and prime the fuel rail. All good.

Cranked right up and made oil pressure.

It was running when I started, and it's running again. Some time and miles before it will be evident whether or not I did any good.

Fuel injectors, Pistons, rings, rod bearings headgasket set, less than $350

 

Good deal. Hope it seals up good with the Hastings moly rings.

Thanks for the Stone gasket picture.

 

Oil change @ 300 miles

Today @ 600 miles:: Retorque headbolts @62fp and exhaust manifold @33fp Every bolt took up slightly.

Recheck valve lash .008in and .012in cold.

Happy with the way she runs. No smoke so far. Another oil change will come @ 1000 mi. All Castrol GTX 10-30

 

Sounds good!

 

Update:: She has run 5000 miles now, and no smoke, or oil consumption.

Hastings rings seem to have seated well.

Just changed oil that had run near 3500 mi, and it was still dark honey colored. Castrol GTX 10W-30. MPG is 20-22.

Down right now, waiting on ball joints and control arm bushings I ordered. UCA bushings finally pounding out after near 300,000 mi.

New parts, genuine Toyota, all the way.