engine knocking?

[MRacer]

I don't know if I ever notice before but when I stand beside the engine with/without the engine exposed I hear a ticking sound. I hear it coming from the engine. At times it's a quiet tick while at times it ticks loud (ok NOT that loud.) However from within the driver/passenger seat, I don't hear the ticking just the sound of the engine. And this is puzzling me. So I spoke to my good cousin Toyota mech and he said he has seen alot of Honda cars with knocking engine. He showed me one and I mean you can really hear it ticking. He said something about piston slapping and it's a bad sign. Then it occured to me. I had an Acura dealer fixed some bad valves (yeap ended up paying ~4k for nice and letting a friend drive my car.) So I'm thinking could they have done something to cause the ticking sound.

So my question to you all is this ticking sound natural? My car only has about 68k on it. For those who's NSX do have engine knocking when did you first experience it and what did you do? I searched the forum and only a few (less than 5) posted similar issues.

Thanks for the help.

-MR

 

[DutchBlackNsx]

Might need a valve-adjustment, which is not uncommon for the NSX.
Also note that injectors can make a lot of noise.
One other thing which seems to be a common problem on Vtec engines, are the 'lost motion' devices, which push youre Vtec lobes up, when they are not used. They seem to become sticky in time.

Mich

 

[nsxtasy]

Listen to someone else's NSX to find out if you hear the same noise.

 

[MRacer]

Thanks. I'll check this out with other NSXs.

-MR

 

[sjs]

Originally posted by nsxtasy:
Listen to someone else's NSX to find out if you hear the same noise.

Great advice. Some valve noise is normal, as is the sound of injectors. But both are best described with your word "ticking", rather than "knocking" which typically refers to a deeper heavier sound and is almost always bad. Piston slap definitely falls under "knock" rather than "tick". As for NSX valves commonly being out of adjustment, I'm not sure that's true. They seem to go very long intervals without significant change, but as already mentioned there are other reasons why the valve train may get noisy.

 

[Jimbo]

Absolutely what everyone else wrote. But could you elaborate on this statement...

Then it occured to me. I had an Acura dealer fixed some bad valves (yeap ended up paying ~4k for nice and letting a friend drive my car.)

What did you pay $4K for? Bad valves? I'm not sure I understand.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[nsxtasy]

Originally posted by Jimbo:
What did you pay $4K for? Bad valves? I'm not sure I understand.

Sounds like a "money shift" (another name for a misshift that revs the engine past redline).

 

[Jimbo]

That's what crossed my mind as well, Ken. That tap, tap, tapping noise (my apologies to Poe) could well be something more ominous.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[sjs]

Originally posted by Jimbo:
That's what crossed my mind as well, Ken. That tap, tap, tapping noise (my apologies to Poe) could well be something more ominous.

I think the point is that the valve damage was already repaired. You may recall a thread on that awhile back. The tick or tap has been noticed since the repair, but he doesn't seem certain that it wasn't there before the "money shift". But still, it could be that the recent repair was incomplete or not done properly. Best bet for him is still to start with a comparison to a couple other cars.

 

[Jimbo]

Agreed. But generally when valve get damaged in a "money shift" it's because they hit pistons.

Perhaps the pistons are OK and perhaps the noise is normal. I just wanted a little more background info so to better advise.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[MRacer]

The dealer just called me this morning and they said it's piston slapping during cold start and it's natural for high performance cars. Say what?! They say they could do an "in-top engine flush" to wash/clean the pistons of carbon, but can't guarantee if this will solve the sound. Another $94 bucks. Ahh, what the hell an I suppose to do now?! I got a few NSX owners in the area will to let me "hear" their engine, but I don't think I'll find anything since they all have low mileage and have never had their engine open. Any other suggestion for poor me?

As for the $4 valve repair job, last time I posted an issue where my friend drove my NSX and he shifted up incorrectly and messed up my car. The dealer cracked the engine and sure enough valves 4 and 6 were slightly bent. They also said there were minor scratches on the piston, but nothing major. I had the valves fix/replace as well as repolish the heads...all for a whopping $4k. I was so sad and piss that I didn't feel like posting my results...sorry.

-MR

[This message has been edited by MRacer (edited 11 December 2002).]

 

[Jimbo]

M,

Piston slapping during cold start is something that just doesn't happen on Honda engines in my opinion. The tolerances and fits are just too good. It's not natural.

The flush/wash they suggest is simply a waste. Don't even bother. The fact that they would even suggest that is troubling.

The noise could be valves and you could solve it with a valve adjustment. That's certainly easily done and not a big deal. It's a normal maintenance item and if they replaced a bunch of stuff it could be reasonable that it needs an adjustment once things have settled in.

However, the noise could be an indication of other piston/rod damage. If there were scratches on the pistons, it's not easy to confirm that no structural damage was done to the piston. Technically, the pistons/rods should have removed and examined/tested. A scratch could be an indication of more extensive internal damage.

If it were my car, I'd adjust the valves and see if the noise goes away. I'd also compare the noise to other cars as mentioned. If the noise goes away with the valve adjustment, or if the noise is typical, then I'd forget about.

If the noise doesn't go away and is atypical...well...I would make plans to yank the engine and really solve the problem. Driving it with slapping/damaged pistons and/or rods is just asking for even more expensive damage.

That's my opinion, FWIW. Best of luck and I hope it's a valve adjustment or a normal noise.

-Jim




------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
1976 Honda Accord 5 spd, 3 door Blue/Blue
1977 Honda Accord - Custom - Under Construction
1986 Chevy Suburban
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[sjs]

So far I'm not too impressed with your dealer, and I'd pretty much echo Jim's comments. The bit about performance cars having piston slap has to do with forged pistons. They start with a greater piston to bore clearance because a forged piston expands more when hot, so they are a bit sloppy in the holes on start up. Of course, if your tech knew his butt from a hole in the ground he’d also know that the NSX has cast pistons and appropriate clearances. So just forget that line of reasoning. I’d ask if they even bothered to listen to it again before that diagnosis but it seems that their opinion isn’t worth much anyway.

 

[Lud]

As Jimbo and sjs have pointed out, whoever you are dealing with doesn't really know what they are talking about as far as the NSX goes, or they are trying to mislead you. Is the dealer telling you piston slap is normal the same dealer who rebuilt your engine? If so, they may just be trying to cover their butts.

First I think you need to identify the noise and whether it is normal or not. It's too hard to try and identify it from a written description. The idea to compare with some other local owners is the best route.

Valve noise sounds different from piston slap. Some valve noise is normal on the NSX. Excessive valve noise means you need a valve adjustment. No big deal.

Piston slap is not normal on the NSX. If you have piston slap, you have a problem. If you can hear piton slap even with the engine hot, you probably have a serious problem.

[This message has been edited by Lud (edited 12 December 2002).]

 

[MRacer]

Thanks for all your patient in explaining this issue to me. It helps me understand a lot about my car.

Yeah, I personally spoke to the guy who looked at it. He's one of their two NSX experts. He said there was nothing to be concerned with since it ticks at cold start and goes away after warmed up after a few minutes. Funny, the contradicting impression I got was "piston slapping is natural … worry when about when it gets louder?" WTF!?

As for the duration of the ticking, it goes away when the engine is hot or has been driving for a while. By the way, what does valve noise sound like?

I called the dealer and they said all the assembly were done by a third-party mechanic shop. The mech shop polished the heads, installed and adjusted the replaced valves, and tested the engine block for leak, etc. The dealer acknowledged the small scratch mark(s) on the piston heads that made contacts with the valves but did not remove the pistons for further inspection. The service guy was nice enough to state they will work with me to resolve the issue if it was something they did wrong.

So I guess I'll be paying some NSX owners visits really soon.

-MR


[This message has been edited by MRacer (edited 12 December 2002).]