ideas on oil consumption issues???

[4AU4LIFE]

For quite some time now, I have been having a oil consumption issue that I can't seem to solve. The car will go thru oil at an alarming rate with no signs of where it is going. I'm hoping that if I give an overview and slight bit of history, someone with more knowledge than me will be able to give me an idea as to what is wrong.
As many of you know, my car had one of the beta versions of the BBSC. Well, things didn't go to well with it and I ended up having the engine rebuilt by an NSX master tech @ 49k miles.
I had no problems for a couple of years with it. Then in the past year or two I have noticed that it seemed to be going thru a lot of oil between changes. Now when I had my Integra, it NEVER burned a drop of oil and NEVER required the addition of any between changes. That is what has/had me so concerned about the NSX having a lust for it.
Granted, the car was strictly a weekend car, or even less usage than that at times, for most of its life with me. Therefore, the oil probably got changed 3-4 times a year. Between those changes, I would have to make sure I kept a few bottles with me at all times. I could easily have to add 3 quarts between changes. If the car was filled to anywhere between the two spots on the dipstick and I drove it for a couple of hundred miles, I would need to add more when I got to destination. That is a scary feeling not knowing how far you can drive till you will be low on oil.:frown:
The car never put a single drop in my garage on the floor or put out any blue or white smoke out of the exhaust.
So, when I got a new DD, I decided to pull the covers and replace the gaskets, plugs, fuet filter and do a compression check.
If memory serves far left plug on front and rear banks gave higher compression #'s than the other 4. The other 4 were with the 10% range. The electrodes of the plugs that came out of those cylinders looked horrible. They were covered in oil(?) and gunk and overall looked worn out. The others actually looked great.(see pics below of the bad plugs).
Well, after 4 months of waiting around, I finally got it back together the other night.
Well, once I finally got it started, I did notice quite a bit of smoke coming from the rear cam cover area. Not having a mirror or being able to get under the car, I wasn't able to exactly pinpoint where it was coming from. I let it run for a few minutes and it continued to smoke. I turned it off and let it set and then did it again with the same results. I also now have a CEL with a code 42 which is a rear O2 sensor. I have been told that when I put in new plugs that the problem would be more obvious than it would be with the worn out plugs.
Today, I started it up and got a slight bit visible vapor fumes out of the exhaust. I let it idle for ~15 minutes and the vapors disappeared. I then got in it and reved the engine and THEN I got some light puffs of very light bluish smoke out of the pipes.
I don't think it would be worth getting a new O2 sensor right now as it would probably get caked up and go bad for the same reason that the other one did that tripped the CEL.
The car now has ~76k miles.
My driving habits are VERY conservative.
Anyone have any ideas? Maybe a leakdown test to give a better idea?
TIA

 

[Daedalus]

Sounds like the oil is going out the tailpipe. That much oil would be very obvious if it was leaking out of the engine. At first blush--and this is just a guess--your valve seals are shot. Another possibility is the oil control rings on the pistons are shot. Sorry, but I think either fix is best done by (or requires) pulling the engine.

Edit: Does the coolant look OK? I guess it's possible the HG is bad, but I'm thinking that's less likely.

 

[4AU4LIFE]

The coolant level has never gone down during this entire time.
The replacement of valve seals requires an engine removal? I was hoping that maybe just the heads could be removed in car to fix this.
If the engine needs to come out for this then the car is down for a long time. I've got more important things to spend $$ on than that right now.
Do you think the engine builder should stand behind the rebuild and maybe offer some assistance of some sort?

 

[Daedalus]

The coolant level has never gone down during this entire time.
The replacement of valve seals requires an engine removal? I was hoping that maybe just the heads could be removed in car to fix this.
If the engine needs to come out for this then the car is down for a long time. I've got more important things to spend $$ on than that right now.
Do you think the engine builder should stand behind the rebuild and maybe offer some assistance of some sort?

I wasn't thinking of the coolant level, just checking to make sure there's no oil in the coolant. Yes, you can replace the seals just by removing the heads, assuming that's possible with the engine in the car (I think it has been posted that it's possible on this car, but I can't remember for sure). And with a trick or two a skilled tech can even replace the valve seals with the heads on. But either way my personal preference would be to have the engine out.

As far as the previous build, it depends on what they did and what their written warranty covers. If they didn't touch what's failing now then they're off the hook. If you're beyond the warranty period then they're off the hook as well.

 

[nsxotic911]

A leakdown will tell you where it's coming from. Give it a try, though I'd have an competent mechanic do it since it requires a special tool and really knowing what you're doing.

 

[4AU4LIFE]

A leakdown will tell you where it's coming from. Give it a try, though I'd have an competent mechanic do it since it requires a special tool and really knowing what you're doing.

That is what I was thinking.
I guess I'll take it to the Acura shop here in town that the company I work for owns so it won't cost to much. Get those results and have a better idea of what exactly is going on.
The rebuild entailed 6 new JE pistons and then new style WP and kept at OEM specs in all aspects including compression.
Thanks for the replies so far.

 

[davidf]

It may just be my poor vision but those plugs do not look oil fouled. They look bad but not oily bad. If the car is burning that much oil, it may soon kill your cats as well. Have you ran your finger in the tail pipe for any residue?

 

[davidf]

Just an FYI, I've seen in the past on various cars, the PCV valve stuck closed due to gunk and when this happens oil gets pushed through the rings from crankcase pressure building up.

 

[nsxotic911]

That is what I was thinking.
I guess I'll take it to the Acura shop here in town that the company I work for owns so it won't cost to much. Get those results and have a better idea of what exactly is going on.
The rebuild entailed 6 new JE pistons and then new style WP and kept at OEM specs in all aspects including compression.
Thanks for the replies so far.

If you're thinking rebuild, budget at least 5K, more like 10k
JE pistons and the word "stock" in the same sentence...are you serious.. There's no way you'll be able to have stock ECU run the same with JE pistons.. just my opinion (and experience)

 

[4AU4LIFE]

If you're thinking rebuild, budget at least 5K, more like 10k
JE pistons and the word "stock" in the same sentence...are you serious.. There's no way you'll be able to have stock ECU run the same with JE pistons.. just my opinion (and experience)

I don't even want to think about having ANOTHER rebuild. I think I would part the car out before I do something like that.
And yes, I'm serious about the JE pistions. When Mark Basch's insurance company paid for the rebuild on it, the refused to pay for OEM pistons as they are only sold as a piston/rod combo for ~$1k each.
The car still runs fine just seems to use quite a bit of oil.
Why do you say you can't run that brand of pistons with stock ECU? Wouldn't you think that if that were the case then the tech would know that and mentioned it?
And you are right, the rebuild was ~$10k the first time and that was with the JE pistons.

 

[Daedalus]

Just an FYI, I've seen in the past on various cars, the PCV valve stuck closed due to gunk and when this happens oil gets pushed through the rings from crankcase pressure building up.

Excellent thought. The PCV should be checked. And I agree the plugs don't look that bad (though if they're different from the others, then something's probably up).

I looked at what one of my engine books had to say about excess oil consumption beyond what has been mentioned (assuming no external leaks).

* Worn piston compression rings
* Faulty oil pressure relief valve
* Excessive conrod bearing clearance (causing more oil on the cylinder walls)
* Plugged cylinder head drainback holes (I seriously doubt this one on an NSX)
* Fuel in the oil, making it thinner and easier to go past the rings/seals

An experienced tech should be able to diagnose faulty rings or valve seals by using a borescope down the plug ports. A running oil pressure check would verify the oil pressure relief valve is good.

 

[4AU4LIFE]

I'll post pics of the other plugs so everyone can see them also.
I'll also go ahead and get a new PCV and see if that does anything.
So would having the leakdown test give us/me a lot clearer picture of what might be the culprit?

 

[nsxotic911]

I don't even want to think about having ANOTHER rebuild. I think I would part the car out before I do something like that.
And yes, I'm serious about the JE pistions. When Mark Basch's insurance company paid for the rebuild on it, the refused to pay for OEM pistons as they are only sold as a piston/rod combo for ~$1k each.
The car still runs fine just seems to use quite a bit of oil.
Why do you say you can't run that brand of pistons with stock ECU? Wouldn't you think that if that were the case then the tech would know that and mentioned it?
And you are right, the rebuild was ~$10k the first time and that was with the JE pistons.

Are they the exact same compression or different compression? Are they the same design? If you answered no to any of those questions, while you can make it work with the ECU, it is not the best idea..

 

[RON98]

That is what I was thinking.
I guess I'll take it to the Acura shop here in town that the company I work for owns so it won't cost to much. Get those results and have a better idea of what exactly is going on.
The rebuild entailed 6 new JE pistons and then new style WP and kept at OEM specs in all aspects including compression.
Thanks for the replies so far.

dude,... leak down is easy.. you can do it yourself.

set piston at TDC on compression stroke, use a leak down tester to put in air pressure. feel for air leaking at oil cap, exhaust, or throttle body.

oil cap = bad rings
exhaust = bad exhaust valve
intake = back intake value

gauge will give you leak down %. if its above less then 15%, dont sweat about it.

 

[RON98]

An experienced tech should be able to diagnose faulty rings or valve seals by using a borescope down the plug ports. A running oil pressure check would verify the oil pressure relief valve is good.

you cant diagnose faulty rings by using a borescope or valve seals information is totally incorrect. Please give correct information or non at all. This leads to confusion and wasted money.

you can NOT see either one of those two components in the combustion chamber with or with out the borescope. The only way you can even diagnose rings using borescope is if the rings is if the cylinder walls are scored to hell. You can easily get the same results with a compression/leak down test.

Also the valve seal is not in the compression chamber and rings are covered by the groves in the pistons this making the "visual inspection" imposable.

here is how you actually diagnose valve seals.

typical sign a valve seal is bad is during initial vehicle start up, the car will smoke for a couple of seconds then stop smoking. Another better test is having the car in gear during deceleration. If the valve seals are worn out, the extreme vacuum generated by the engine with the throttle body closed will pull oil past the valve seal from the top end and your vehicle will smoke on decel.

For piston rings, do a compression and then a leak down test. If rings are toast you'll have lots of air coming out of your oil cap hole.

Hope i pointed you in the right direction instead of wasting time with a bore scope.

The PVC valve should be checked first since it is the easiest thing to do. Build up of gasses in the crank will lead to improper ring sealing.

here is another possibility.

during the inital engine brake in, you took it way to easy on the motor and glazed the cylinder honing before the rings had a chance to seal and mate.

Some engine builders sware by WOT the engine as soon as it is started and putting it under extreme load.

The theory is the compression gasses will force the rings against the cylinder walls and this will quickly mate the rings to the cylinder BEFORE the cross hatching is glazed over.

If you ran the car according to factory procedure of running it real easy, that could have cause your rings to not seal right because the factory piston ring material is soft and not as hard as the stuff that comes with the aftermarket rings so the AM rings does not seal like the softer factory rings will and require more force to brake in

Im braking in my new engine with the beat it to death method. You can google it and find great results.

it makes complete sense.

What i would do is verifiy that the engine first does not have any compression issues or a scored cylinder wall. If all checks out and just bad ring sealing ( more importantly its across the board). I would go out and WOT the crap out of it and hope the extra force on the engine seals it.

driving conservative could have been your down fall here.

also take my advice with a grain of salt. do it at your own risks. I do not know the condition of your motor and it is up to you to verify the WOT worthiness of it.

good luck with it.

 

[ftuhy]

Somebody already suggested the PCV valve, which would have been my WAG as a simple thing to check/replace. I definitely would go back to the shop that did the rebuild and ask them to stand behind their work.

As to code 42, that's for the heater on the O2 sensor. For codes 41 and 42, from experience I can tell you it does not affect operation, although at times the TCS light may come on with the CEL. The heater only gets the sensor into its ideal operating temperature sooner. Once the engine is warmed up, it has no effect. I could bring my engine all the way up to 8,000 rpm with the code in effect. So, I wouldn't even bother replacing the sensor until after you solve the oil consumption problem.

I change my oil once a year (3,000 to 4,000 miles), and can't even tell the difference in level on the dipstick from start to end. I don't race the car, but is usually sees the redline a few times on every drive.

Note that I had a Corvette (1964) with 146kmi that used oil at the rate of one quart per thousand miles. At 125 mph, the exhaust was mostly blue smoke. It seems like you are using oil at an even higher rate.

I haven't looked at the ring design for an NSX, but on many cars one side of the compression ring(s) has a bevel. Is it possible the shop installed the new rings upside down??

 

[Daedalus]

you can NOT see either one of those two components in the combustion chamber with or with out the borescope.

Correct, you cannot see the rings or the seals. But you can see the signs of either oil blow-by on the cylinder walls or oil drippings from around the valves.

 

[4AU4LIFE]

Ok, so tomorrow I plan to get/order a new PCV valve and see what that does.
I'll see if I can find the sheet where I wrote down the exact #'s for the compression check but I know 4 were almost exactly the same and 2 of them were a bit higher.
I guess I'm still miffed as to were the oil could possibly be going though. If it isn't thru the exhaust or leaking onto the ground then where is it disappearing to???
When I started it up the other day and got the couple of plums of smoke, I did get a few drops of water out of the passenger side tailpipe.
When I have washed the car in the past, I never noticed any unsually large deposits of any sort on the exhaust tips.
I found my receipt of when I had the work done and the rings that were used were JE also to match the pistons. The PCV valve was replaced at the same time along with WP and timing belt.
I have contacted the shop to inquire about warranty and how they felt about it because it didn't seem like it was that long ago. However, it was 26k miles and almost 6 yrs ago. So, I honestly don't feel as though they are responsible in any way or should provide warranty that long ago. That means I only drive the car ~4200miles a year.:frown: I really wonder whether I should just fix it and sell it so someone else can drive it and enjoy it more than I do.
Heck, it is almost time to do the WP/TB again simply due to time and not mileage.

 

[4AU4LIFE]

Are they the exact same compression or different compression? Are they the same design? If you answered no to any of those questions, while you can make it work with the ECU, it is not the best idea..

To my knowledge, they are the same compression. I WAS thinking of going low compression so I could run boost at a later time and then changed my mind.
I honestly have no idea about the design. There again, I would HOPE that if they weren't the correct type for the car, the Master NSX tech would have said something and NOT allowed them to be installed.

 

[Daedalus]

I guess I'm still miffed as to were the oil could possibly be going though. If it isn't thru the exhaust or leaking onto the ground then where is it disappearing to???

I think we all more or less agree it is going out the exhaust. What needs to be determined is how/why the oil is getting into the combustion chamber.

A PCV is cheap, but it's also easy to diganose. A procedure is given on 11-134 of the '91 manual. On most cars you can pull the valve or a hose going to it and listen/feel for a vacuum and air movement. Aside from possibly wasting money on a part you don't need, you also won't know for a while whether you fixed the car by replacing the valve.

 

[ffffanman]

Welcome to my nightmare!
Your oil is going out of your exhaust dude.
I'll bet money on it.
Not enough for your engine rebuild though!
Do a proper compression test and a leak down test.
Who rebuilt your engine.
You can have my old set that had to get torn our of my car.
I now have Weseco 90.75mm 9.8:1 CR with Xylan skirt coating.
Don't eat any oil, the other pistons..I'm checking to see what they where......about a quart every 150 miles.
Listen to Ron98!
Trev

 

[nsxotic911]

Welcome to my nightmare!
Your oil is going out of your exhaust dude.
I'll bet money on it.
Not enough for your engine rebuild though!
Do a proper compression test and a leak down test.
Who rebuilt your engine.
You can have my old set that had to get torn our of my car.
I now have Weseco 90.75mm 9.8:1 CR with Xylan skirt coating.
Don't eat any oil, the other pistons..I'm checking to see what they where......about a quart every 150 miles.
Listen to Ron98!
Trev

Ditto, listen to Ron98 (probably one of the best free technical troubleshooting on this forum)

 

[4AU4LIFE]

I think we all more or less agree it is going out the exhaust. What needs to be determined is how/why the oil is getting into the combustion chamber.

A PCV is cheap, but it's also easy to diganose. A procedure is given on 11-134 of the '91 manual. On most cars you can pull the valve or a hose going to it and listen/feel for a vacuum and air movement. Aside from possibly wasting money on a part you don't need, you also won't know for a while whether you fixed the car by replacing the valve.

I have the Helm manual so I'll follow that procedure listed and see what happens.

 

[drew]

The blue smoke ON START UP is generally a sign of bad valve guide seals.

If it were the oil rings, the blue smoke would show up on running starts (like a stop sign).

A compression or leak down test may not show anything conclusive on a issue like this.

Based on the information at this time: my money is on the valve seals. You can replace the seals with the engine and heads in place, it won't be easy, but it sure beats taking out the engine for a shade tree mechanic. You won't need an air chuck, just work on each set of valves when the piston is at their relative TDC.

However, the guides or seats could be unhappy too. If that is the case, then somebody botched the valve adjustment by making the clearance too tight. (IMHO, it is not even worth doing a valve adjustment on the NSX, there is more chance of the tech screwing it up than the valves going out of adjustment).

You might be able to test for bad valve seals by cleaning off and reinstalling the spark plug after a warm engine. Let the car sit all night, pull the plug and see if it is wet. This may not work on the NSX because the oil might not be able to drip on the spark plug. Maybe somebody who has a pulled head on the car can run a test by filling up the valve guide with oil and see where it drips...

Drew

 

[ffffanman]

I see what your saying Drew, and have thought the same, but my money is still on Pistons and Rings. I say $200.00 US on pistons and rings and the money is going to 92NSX for the rebuild....lol.
Lets hope for valve job though.
Trev