big bear

90 Runner 4x4 5 speed 3vze.

Engine was rebuilt in June, has 1100 miles on it now.

Last week it developed a miss so I did a compression test on it yesterday.

Cylinder Pressures.
1. 120psi
2. 120psi. burnt oil on plug, comp tester tip oily after test.
3. 120psi
4. 120psi
5. 120psi
6. 5psi. plug fouled with burnt oil, comp tester tip oily after test.

I live at 7000' elevation, so I think the 120psi is about right.




Sorry the pic quality is so low, camera won't power up.

Ryan G.

so what do you want us to say? are you looking for a diagnosis? I would hone in on the valve train. Maybe pull off the valve cover and recheck your valve adjustments and verify proper operation. Something is not right with the exhaust valve in cylinder #6. Do you have compression in that hole?

big bear

5psi in #6 cylinder

Crappy ITM gasket set was used, I learned of their poor quality after the install.

I'm thinking of having a leak-down test done, that should determine if it's the rings, valve seals, or HG.

big bear

Took the Runner to my local mechinic this morning, he has worked on quite a few 3vze's.

He seems to think that the build up on the plugs is fuel not oil.

He said the problem is valve clearance, sometimes Honda and Yota valves seat deeper after break-in after rebuild, and since there are no shims installed on my lifters he said the hockey pucks will need a little grinding to restore clearances to specs.

big bear

I'll check the valve clearances soon, gotta pull the valve covers anyway they are both starting to leak, he said the plastic valve covers warp over time, and grey RTV should be applied to both sides of the valve cover gaskets and allowed to tack up before install to prevent them from leaking again.

I'll post up the clearances as soon as I do them.

big bear

Reviewed my notebook, valve clearances for cylinders #4 and #6 intake and exhaust, all were 0.010(inch) at time of re-assembly.

Gamefreakgc

Technically, intake should be between .007-.011" and exhaust .009-.013", but .010 across the board will do the trick.


Some people try and read spark plugs like a shaman reads animal entrails, but it's not always accurate. A fuel issue doesn't result in 5 Psi. Either your valves are stuck completely open (not very likely), you broke a valve (also not likely), or your piston ring on the cylinder is shot (likely). Take a bit of engine oil and put in it the cylinder in question and do the compression check again. If it improves, it's your piston ring. If not, do a leak down test. Don't rip your engine apart just to check valves again when it's probably not the issue.


And yes, the mechanic is right about the RTV. I recommend going and buying Toyota FIPG, it really is the best stuff for the job. I've used both and the Toyota stuff is thicker, more heat resistant and sets in minutes, not hours. See page EG2-80 on where to put it:


http://personal.utulsa.edu/~nathan-b...68cylinder.pdf

big bear

Thanks for the reply Game.

I'm going to check the clearances on the left bank, pretty easy to get the valve cover off, just remove the air intake hose that connects the plenum to the air filter box.

The mechanic seems very sure it is a valve clearance problem, he's the lead mechanic and he runs the shop, 16 years experience.
I'm thinking it's the rings like you do, but why would the rings fail after only 1100 miles ?

This is the third time he's looked at my truck, NO CHARGE.

The spark plug in #6 was out of spec ohms wise, he had the parts store bring over a new one, again no charge to me, he obliviously isn't trying to make money off me.

So by checking the valve clearances will kinda tell me if the mechanic really knows what he is talking about.

The machine shop did all the internal work, they've been in biz since the early 80's.
But on the other hand they did talk me out of buying a Fel-Pro gasket set and buying a crappy ITM set instead, he prolly makes more profit off the ITM stuff.
Sure wish I knew about ITM's rep before I started my rebuild, well live and learn !

big bear

If it is the rings other cylinder will prolly start failing too, SWEET !

Gamefreakgc

Not necessarily. #6 is known to fail faster because it is exposed to more heat due to being in the back and that silly exhaust crossover pipe that heats the back of the engine. If anything, #5 might start to show issues down the road, might not.

The reason why I think it's the piston rings and not the valves is because of your PSI rating. If it were a leaking valve seal, you'd get a mucked up plug like that but still have decent compression. However a bad piston ring would result in very low PSI like what you have and also allow oil into the combustion chamber. I'm not a mechanic and your guy seems like an honest guy, so don't think that I'm infallible.

big bear

Alright here's the clearance measurements for the left bank.

Cylinders.

#2 <.006, >.007 Intake .012 Exhaust

#4 .012 Intake .009 Exhaust

#6 .011 Intake .008 Exhaust

At install after they came back from the machine shop before first start-up.

#2 .011 Intake .011 Exhaust

#4 and #6 .010 across the board.

big bear

The oil is much darker than it should be.

What do you think the chances are that the machine shop will replace the rings under warranty,LOL.
I know they'll find some way to weasel out of doing any warranty work.

I'm going to go dig up the warranty paper now.

You da man Game, I do trust your opinions and advice, thanks bro.

big bear

They only give a 90 day warranty on short blocks.

big bear

Here's my plan of attack.

Pull the motor, pull the left head off have it microfluxed and the valves adjusted, put a new Fel-pro HG and head bolts on, replace rings in #2,#4,#6 with chrome rings.

Sound like a plan ?

What would you do ?

I'm on a very limited budget.

superex87

If your only getting 5 psi on #6 you have a valve problem. Put oil in the cylinder before you take it apart! Being on a limited budget means you need to FULLY diagnose what is wrong before replacing parts. My bet is the exhaust valves are original to the engine and the exhaust valve of #6 is cracked/ chipped. A 15$ valve and a headgasket is not too bad vs new rings/ block work.

I would also highly recommended reworking the exhaust cross-over so #6 and head gasket problems are no longer a issue.

Ryan G.

after seeing the 5 PSI in cylinder #6 and thinking about it more I'm bad rings camp. Having said that I agree with superex87 in fully diagnosing it before just tearing it down. It really could be something simple.

big bear

Thanks gents, I agree I need further diagnosis.

I'll try the comp test with oil added to the cylinder tomorrow, I'll post the results.

See what that spark plug looks like too.

I am correct that chrome rings are more durable ?

RSR

A little late to the party, and I haven't actually had to get this far into this on my own engine, so this is theory not personal experience on the 3vze...

That said, for piston rings, my understanding is as follows:

Chrome are really only for high RPM, high heat engines like turbos. Additionally, they require fresh, perfect spec bores and/or rebored engines prepared specifically for chrome rings -- I think this means cylinder walls might need specially prepared coatings due to chrome's hardness and smoothness, need to ensure adequate oil reaching rings since chrome doesn't carry. Probably not what you're looking for. I think turbo diesel type engines in dirty, high wear work/service environments are primarily where chrome rings are used these days... Not very common in American passenger vehicles as I understand it. Ultimately, chrome take forever to break in and require high heat to properly seat, so that's a major drawback unless you're going to pay a tuning shop to run a proper break in on their dyno machine or something along those lines with open, low traffic roadways allowing you to accelerate and decelerate with engine breaking etc, avoiding idling for a couple thousand miles...

I believe the OEM factory rings are ductile iron, moly coated. This is what I'd recommend you replace with, provided the machine shop actually re-bored and honed (essentially an overbore) all cylinders and didn't just remove the glaze with a brush or glaze breaker. If they did the latter, you want to to go with a cast iron ring. Ductile moly rings last longer than cast iron as the moly coating means the piston rings and engine cylinders aren't wearing as quickly -- cast iron essentially micro weld themselves to cylinder walls during operation leading to quicker wear of rings and engine walls. The moly coating prevents this micro weld and moly itself, being somewhat porous carries a lot of engine oil between the ring and the cylinder wall as well. The drawback of moly is that it can carry dirt and other contaminates too, hence the need for good air and oil filters -- preferably with the addition of magnetic drain plug, filter sleeve, etc, to remove ferrous particles smaller than your filter can grab from from your oil stream.

Hastings has a pretty good brief: http://www.hastingsmfg.com/ServiceTi...ecommendat.htm

sphealy

iTrader: (1)

Did this issue ever get resolved? Just curious of the outcome.

big bear

Not yet.

My 95 Grand Am blew it's LIM gasket, so it's the one getting my attention ATM.

The Runner is plugging along on 5 cylinders for now.
Only drive it to work (2 miles) and the grocery store (1.5) miles.

The smoke sure smells funky at start up, not just gas and oil burning, I know that smell, I think there's a little coolant burning too.