Too Much Blowby

[bonestock]

Hey guys. This is my fist post to the board. I’ve been on jeepboard.com for a few years and it’s been a great forum, I hope I’ll have the same luck here. I know the jeeps forwards and backwards, but the nsx is a little different.

Sorry about the length, it was unavoidable.

The nsx is a 98, 6spd. It has about 59k miles, it got a new short block about 15k ago due to a bad main, all work done under warranty by an acura dealership. This took place with the previous owner who is supposed to have taken good care of it. Mobil 1 has been used since it was purchased used (around 50k miles).

The car belongs to my dad, that’s the only reason why it’s gone to a stealership service department. Took it to acura 101 west in calabasas, CA for scheduled maintenance. One of the things that they were supposed to check out was a white powder coating the inside of the intake duct. They gave some bad excuse about “road debris” and probably didn’t even check it. You could wipe this stuff off with your finger, bad stuff. I took it out to wash it out today, and noticed that the air filter was extremely dirty. In the process of replacing it, I was going to clean the throttle body (TB).

Upon removing the intake duct, I found there was a little bit of oil residue on the nipple on the intake duct that connects to the PCV inlet line that goes to the forward bank valve cover. There was not any oil visible in the rest of the duct. I found that there was an a little bit of black stuff coating the walls of the TB, not too much to the eye, but visible on the rag I used. Most of it came from near the butterfly. I looked past the butterfly and it was dark, waaay dark. So I took the TB off and the intake was coated with black stuff, enough that I could scrape it off with a fingernail. The back of the butterfly was also gunked up.

The engine doesn’t eat any noticeable amounts of oil. The PCV valve on the back bank valve cover is working ok and isn’t gunked up. It will let a little bit of air past when it’s supposed to be closed, but not a huge amount.

Basically I’m looking for any experiences or suggestions. I know that checking the plugs, a compression test and a leakdown test are in order. Not to mention cleaning out the intake manifold, and comparing the PCV valve to a new one.

I know that a little bit of black residue in the TB is normal, but this was too much.

Maybe the mess is from the original engine build/failure?

I thought these engines were supposed to be rock soild?

 

[satan_srv]

well it runs fine doesn't it? Is there really a 'problem'?

Sounds like your air filter needed to be replaced badly and result in the gunk in your intake... Just clean it out and see if it comes back. Probably won't with a new filter

 

[bonestock]

to clean this out, it's probably going to require removing the intake manifold. not a huge deal, but not as simple as just wiping out the TB throat.

i don't see how the clogged air filter could cause the buildup of, what i presume is oil, past the TB. unless the flow restriction was causing the PCV system to malfunction. the pressure difference required to run the PCV system should be present whether or not the engine has to suck harder because of a clogged filter.

 

[Larry Bastanza]

Try the simple way, you will like it.

Go here:

http://www.nsxprime.com/forums/showthread.php?s=&threadid=33671

HTH,
LarryB

 

[bonestock]

thanks for the replies so far.

it's not the cleaning that bothers me. rather it's why there is so much buildup in there. unless the stock engine is extremely high-maintenance, the intake manifold shouldn't have to be thoroughly cleaned of large amounts of gunk after less than 60k miles.

there don't seem to be any noticable engine problems. i tried to check for DTC's that weren't triggering the check engine light, but my obd2 reader wouldn't work with the nsx. it just said "E." it's for all obd2, and i have used it on foreign and domestic vehicles. hmm, another mystery.

anyways, what do your intakes look like on the inside? are they pretty gummed up? i'm a bit apprehensive about trying to just blow it through the engine, there's a lot, and i don't want it fouling up.

 

[ScienceofSpeed]

The white residue to mold release and oxidation. This is ok, and normal. The slight residue you saw is also normal. As Larry mentioned, it can be cleaned out. As an alternative, the throttle body can also always be replaced with a ScienceofSpeed Big Bore throttle body, which uses the stock throttle body as a core. The Big Bore throttle is thoroughly cleaned and brought to new condition.

http://www.scienceofspeed.com/produ...roducts/NSX/ScienceofSpeed/NA_tune/induction/

take care,
-- Chris

 

[bonestock]

thanks for the input.

when i took the TB and the spacer off, i found that there wasn't as much junk as i originally thought. i got as much as i could reach with carb cleaner and a rag. it looks a lot better than it did.

regarding the powder on the duct, even though it's a normal part of manufacturing, as far as i'm concerned anything that's loose enough to be wiped off shouldn't be past the air filter. it's easy enough to clean out with simple green and a brush.

i think a new PCV valve might be in order, as it doesn't close 100%. that and the nasty air filter were probably responsible for the excessive gunk.

i just wish i knew about this ahead of time so i could have gotten a UNI instead of wasting $67 on a junk paper factory air filter!

 

[sjs]

...i just wish i knew about this ahead of time so i could have gotten a UNI instead of wasting $67 on a junk paper factory air filter!

What makes you think it is junk? I'm not a blind worshiper of EOM NSX parts but I think you will find that the stock air filter is equal to or better than most in terms of filtering (which of course is it's purpose), and entirely adequate in terms of breathing.

 

[bonestock]

i think that, in general, paper filters and gauze filters are both a waste. the former is restrictive and clogs easily, the latter lets too much get past it.

foam filters are proven in the harshest conditions, and they flow better than paper for sure. and they're reusable. i got the UNI for my jeep for less than i paid for an nsx stock filter. every time i change the oil, i also have a brand new air filter for the cost of some simple green and filter oil.

after all, every off-roader can't be wrong!

 

[Larry Bastanza]

The stock NSX air filter has been dyno proven to be as good as any filter. Aftermarket filters even drop HP numbers. If you paid $67 you need to look around here for discount pricing.

Most other filters require maintenance and offer "0" benefit over the stock filter, well maybe a sound change if you want that. Maybe a K&N filter or the like, give better results for a Camaro V8 (not knocking them by any means), orwork good on the BAJA, but no sale here for the NSX. I consider 30K miles for filter changes fine, with no ill effects.

My $.02
LarryB

 

[sjs]

i think that, in general, paper filters and gauze filters are both a waste. the former is restrictive and clogs easily, the latter lets too much get past it...

I think that, in general, you are mistaken about paper filters. They have decades of R&D and when designed appropriately are only as restrictive as needed. It is a common mistake to assume that less restriction is always good. Get Dad's car on a dyno and do a few runs with and without a filter. I'll bet you don't see an improvement and you may even see a loss. Do you really think Acura put all that time and technology into the engine only to leave easy HP on the table with a crappy filter?


The best oiled filters when properly maintained are very good, but offer no meaningful benefit over the stock filter. As for the cost savings, I really can't take that seriously.

 

[satan_srv]

when designed appropriately are only as restrictive as needed. It is a common mistake to assume that less restriction is always good. Get Dad's car on a dyno and do a few runs with and without a filter. I'll bet you don't see an improvement and you may even see a loss. Do you really think Acura put all that time and technology into the engine only to leave easy HP on the table with a crappy filter?

You're probably right in this case, but sometimes designers sacrifice power for things like sound and NVH etc. Acura probably pulled off both in this case but usually open element filters show gains over closed systems.

 

[bonestock]

i'm sure acura was more careful with the nsx's intake than most common cars, as the airbox is shaped fairly well. the pre-airbox intake duct however looks like it was designed for resonance reduction and keeping water out, instead of free-flowing intake. i still contend that the uni is a better filter. maybe the nsx filter in particular is better than the average paper filter.

of course it won't run better if you pull out the filter. it'll run lean until the computer gets new values, and with no intake restriction, the restriction of stock mufflers and cats won't help either.