My 2003 coupe has piston slap. It sounds like a diesel engine at start up and when cold. After warming up however, I still hear what sounds like a noisy valve train beginning around 2200 rpm through around 4000+ rpm. Is this still the piston slap, or do I have faulty knock sensors? I've read threads on piston slap, but most say the noise goes away after warm up. Will faulty knock sensors throw a code?

Thanks for any help!

 

Faulty knock sensors will throw a code. Look in the code list.

 

No codes popping up on my DIC. So I guess it's just the piston slap at those mid-range rpms.

Thanks!

 

Engine knock, more precisely called detonation, will have more of higher-pitched metallic sound than the piston slap sound.

Detonation is more likely to be noticed in a hot engine under load.

 

That's when I hear it. Under heavy acceleration pushing the engine through the mid to high rpms. Sounds like all of the valves are pinging. FYI - I run quality 93 octane fuel.

 

Are you running a stock tune? If yes, you probably just have a carbon build-up on the pistons or combustion chamber. A Seafoam treatment will probably help to get rid of the carbon.

 

Stock tune, but only 39k miles. Another owner put 34k miles on it so I can't say how its been driven in the past. For me, highway and a little spirited driving. Can carbon build-up occur that quickly?

 

Yes, it's very possible at only 39k miles. Does the engine burn any oil?

 

Nope, not a drop. I use Mobil 1.

 

That's good! Oil burned will tend to build up carbon in the combustion chambers very fast.

I would try a Seafoam treatment first. It can't hurt anything, and it's cheap enough.

 

Will do. Hey, thanks so much for taking the time to help me out! This forum is always a great place to get some advice.

 

Always glad to help! Let us know how you make out.

 

I absolutely agree with the Seafoam treatment. I have a 99 with 133K on it and had very similar sounds coming from the engine. I purchased the Seafoam in the spray can with the little straw setup to spray directly into the TB. It worked amazingly well. I was ready to change sparkplugs, wires, thicker oil, etc. to stop the noise. Now it is as quite as when I bought it.

 

Normal

 

Normal? Which, the noise or carbon build up? Does your Vette have the sdame issue?

 

Can you explain the noise at 2200 rpm better. Is it like hearing popcorn pop in a metal bowl. Cause I have that when it is warm out and would love to get rid of it.

 

2003, minimal piston slap, do to accu-sump and pre-lubing block

Run M1 15-w50

Carbon build up? none, I run fresh fuel and beat the chit out of the engine.

Carbon build up happens on engines that are run in lower rpm band, or cheap fuel, fuel with poor additives that really dont clean

Clean you engine, buy some fresh fuel, ie find a station with the long lines, Fresh fuel not top tier stuff

I use Sheetz or Hess most of the time.

run a gear or two lower, keep those rpms UP, for a full tank. that carbon build up will be burned up.

gear wise, for manuals go cruse the highway in 3rd gear 65-70 mph, not 6th

autos, find the appropriate gear for 55-6000 rpms at 65-70 mph
YES fuel mileage will suck, but it will clean out the engine.

We have pulled too many heads off cars, that were lightly used vs race engines ( all on 93 octane) those lightly used heads were carboned up vs the race engines were clean as clean can be.

higher rpm engines are happy clean engines.

top tier fuels have additives for cleaner engines and fuel millage would be my guess, not really performance fuels.

 

That would be it. I'm going to try the suggestions in this thread. I'm thinking I have carbon build up.

 

I agree totally. I've been "de-carbonizing" my engines since '65. (necessary evil... )

 

We must be of the same special vintage! I started my "de-carbonizing" back in '64, with a '57 Chevy.