knocking sound holding around 3,000rpm
 

Today I drove about 200mi on my way home today, about 70mph the whole way in 6th gear. When I got off the interstate I was driving in 4th gear holding about 3,000 rpm where you normally hear a certain burble of what I guess is the AVCS changing, well holding it at 3,000 rpm it slowly went from normal to a light knocking noise. I went back through 3rd - 4th gear again and again it went from no noise to the same rattle.

Only thing I could gather is the car is hot and tired, and the expanding metals are creating a noise that the car isn't adjusted for. The car felt pretty limp for a minute too, but that might be placebo from coming off the interstate?

Anyway let me know if this is just some fault of the engine adjusting or if I'm experience a real rod knock. I have no idea if the dealership has done any ECU revisions, likely the have not. 30+k miles all stock.

Well, radroach, I'd check the crankcase oil level to make sure it has enough oil.

If it didn't throw you a code and it doesn't happen again, I'd just forget about it....;)


humfrz

Oil levels on the dipstick are good

Hi all want to report that the issue earlier hasn't come back all weekend. Car's been running good.

yet if it does again I'll post again in this thread with video.

Silly thought - maybe pull all the jack and parts out of the trunk. It's not really that well secured, so it may be from a simple RPM or resonance vibration.

It was definitely from the engine at the time. I can definitely tell difference from rear noises from the front (as my license plate vibrates a little bit). I've also got the sound tube still, and get to listen to engine noises all the time. This time it was definitely a noise that didn't sound good, a pinging or rattling noise. I noticed it first when going downhill at around 3k rpms and holding it there, it turned from the normal noise to a rattle.

BTW this isn't the first time it's been reported http://www.ft86club.com/forums/showthread.php?t=13827

I'm going to take another guess here, I think the plastic cover over the intake manifold is loose. I took it off a week ago for cleaning and now it has a bit of play in it.

Also took the same 200mi trip back today and it started again a little while after driving in the city. Same sound, happening about 2k rpm, tried to film it but it wasn't picking up over the road noise.

So I'm going to take the cover off, or wrap some electrical tape around the slot to see if it dampens the vibration and holds it together. Will make another post later.

I'm going to revive this thread. I've been noticing exactly this sound for a couple weeks now. It's definitely the engine or in the engine bay. Very frustrating because it comes and goes. Cannot reproduce it at will.

The knock happens mostly when I'm steady-state cruising in fifth, sometimes fourth, and the engine is running around 3000-3500 RPM. If I either apply throttle or release it, the sound disappears.

Could be a knock sensor but that would usually throw a code. This is an interesting one...

Definitely not detonation/ping. I found an old clip taken by JimmyMac here. He never found the source and has since installed a turbo sooo... :iono:

I'll keep looking.

Sometimes I think I hear a similar sound too when cruising between 3-3.5k rpm but when I go to turn the music down to hear it better it's not there. Maybe I move my foot on the throttle and it goes away... I think tomorrow morning I'l keep the tunes off for a while and see if I hear it.

problem hasnt returned since it happened to me, but I'd still like to know what it was.

[ame="https://www.youtube.com/watch?v=eqrlwMgfqtY"]FRS BRZ GT 86 DI Failure - YouTube[/ame]

Damn! That's exactly the sound at about 0:26. I don't hear mine while accelerating, though. Only when I'm running steadily.

Did yours become more obvious over time?

Thank you. I will look at DI as well.