Brief rattle when getting on the gas at specific RPM.
 

Hello,

I have a 2017 stock 86, and I've noticed in the last couple of months a rattle that's starting to concern me.

When cruising at around 2.5-2.8k rpms completely off the gas, the moment I start accelerating there is a brief (<0.5s) metallic sounding rattle/grinding noise. The sound is louder when the windows are down. Also, it doesn't always happen. Sometimes it is extremely noticeable, and I can consistently reproduce the noise. Other times it is very quiet, or doesn't happen at all.

Every gear will cause the rattle, but I've noticed that higher gears are worse. My guess is because higher gears take slightly longer to leave the RPM range of the rattle.

I'm planning on taking the car in under warranty for a squeaky clutch, and want to explain this problem too. Has anyone ever experienced something like this?

I used to get a rattle in a 500 rpm window (I think between 1.8-2.3k). Based on everything I read, my best guess was a small piece of the cat in the header had broken off and was resonating at that specific rpm. After switching headers, it went away. Whatever it was, it was in the header.

Heatshield on the exhaust or your headers. One's gotta be loose somewhere. I'd start there.

I also have a rattle that fits the same RPM range, not sure if it developed or I just noticed it one day.


Driving a year with it since and have done 2 oil changes, no metal flakes in oil so don't think it's a serious engine issue.



Stopped caring

https://www.youtube.com/watch?v=iuEw...ature=youtu.be

Found this video in another thread. Sounds exactly like this.

I try to ignore it, but every few weeks it starts bothering me again and I can't stop thinking about it...

That's me. Thread with latest findings is:

http://www.ft86club.com/forums/showthread.php?t=129526

I'm not willing to ignore it as "no big deal" yet. I can't do that without knowing the what and why.

Right now my big issue is that it's hitting the knock sensors 4x per 720 degrees of engine rotation which is the worst it could have been. So it's on all 4 cylinders... Which event in which stroke though!? With only a 2ch dso, it sucks that I can't graph more things at once, I'll have to keep at it with with only a knock sensor and one other thing until I see something that lines up.

I have exactly the same rattle you're describing on my '17. Was in for an oil change at the dealer last week and asked them to check the heatshield or if anything was loose under the car and they couldn't find anything. Oh well.

CA is california ?? likely 91 fuel

a metalic rattle like ball bearings in a tin can under acceleration in the 1500-3500 rpm range is likely knock/detonation

I noticed this sound since 2013 and just heard it as recent as yesterday. I can also usually recreate it on demand by releasing the gas pedal and then pushing it sharply. I can also consistently make it not happen by easing into the throttle instead. The only mechanic (not Toyota) that looked into it for me said he thinks something in the drive train maybe more specifically in the differential area rattles when sudden throttle is applied. Gave up on trying to figure out what it is after that. Car is driven daily for 6 years no issues as I personally don't consider it an issue since it has hasn't got worse and doesn't seem to affect performance.

I've been looking into it for just a few hours in my spare time and I've already eliminated the entire drive line.

Knock sensors pick it up, it's in time with engine strokes. Look at the thread I linked previously.

i had the same issue on my 17 brz.. i brought mine to the dealer to have it checked out before. the second time i went, the technician said it was the HPFP so they had that replaced under warranty.

i could say the sound is not as consistent anymore as it used to be but i did hear it once or twice VERRYY very faint ever since i had it replaced. maybe i could be wrong lol, but yeah this sound is now common apparently? ive seen quite enough brz/86/frs owners that experienced the same "sound" for years and not once it caused a real issue.

Huh, interesting. Going through the thread, it seems like the method of reproducing this noise is consistent with generating my issues in this thread I posted a little while ago: http://www.ft86club.com/forums/showthread.php?t=130624 (My first post is slightly outdated because at first I thought it was gear 2 only.)

Basically, I get a hesitant acceleration that I can both feel and hear when cruising at ~2.1kRPM before giving it anything harder than a smooth acceleration. I can see my tachometer flutter (only tested this up to fourth gear but I can see it waver VERY visibly and I feel the entire car "shudder" a bit too).

The thing that stands out is the SOUND that people have pointed out. Notably in the video cat94 linked which isn't *too* far from the sound I have heard from time to time. I would not describe mine like a rattle but more like a slight "hiss" and "click" as if something were turning on. I sometimes get that sound when my car is still warming up and I get that "flutter" issue I describe in that range. My issue of acceleration still persists after driving the car for an hour though my unscientific observation seems to feel that the flutter is less persistent when warmed up.

I chalked it up to the direct injectors kicking in suddenly (and maybe poorly?) when giving it a sudden burst of gasoline.

Now mind you, mine is a new AT 2019 86. I don't know anything about the BRZs and if they received the same updates as the 86 did when the FRS moved over to Toyota for the 2017 models.

Try this. Cruise exactly at the 2.1-2.3K RPM range for at least 5-10 seconds (this is important, because of the following paragraph!), from gear 3-4. Give it a sudden burst of throttle (moderate to high), and HOLD it so you can feel the acceleration. I am able to reproduce my flutter issue in this range a good 90-95% of the time. Do you get a steady acceleration? Note how long your engine had been running at this point.

I'm not an engineer so grain of salt folks (and feel free to point out of I'm totally wrong), but based a few assumptions garnered on that one video I saw on the 86's engine from toyota, the port injectors work in the lower RPMs, swap to direct for higher, then use both at the highest RPMs for more power. I believe that when you cruise at the lower 2.1-2.3K RPM range (I have not tested it at higher RPMs consistently) that it'll eventually swap over to the ports, but with sudden acceleration it immediately jumps over to direct injectors and causes that sound (and for me, that issue). A more smooth or gradual acceleration mitigates this flutter to the point where it's not there for myself, but I do NOT get this noise unless my acceleration is sudden. Edit: People have also stated that when they leave off the throttle before gassing it again reproduces this issue. Do you people generally know what RPMs you were around between the off and on of the throttle? Personally, I think there's an injector issue that could either be due to ECU doing weird things to it, or the injectors themselves.

If you don't let it cruise for at least a few seconds at that stated RPM range, and I was coming down from a higher RPM only to immediately give it more gas and throttle and bring the RPMs back up again, I do not get a flutter, nor a noise and my acceleration is as smooth as butter.

In short: cruising at ~2kRPM steadily followed by moderate but sudden throttle = noise/flutter issue for me, noise being secondary to the flutter and not as consistent. More notable during engine warm up. That being said, I believe the sound and flutter issue for me are strongly correlated. I don't have a problem with the sound, personally. It's that jarring "jumpiness" that bothers me.

Otherwise I've had no issues with the car. I've been daily driving it and loving it regardless. For now I've decided to live with it as I've had no CELs and others have stated their car is just fine without it. After I break in the car I'll put it through its paces and probably take it to the dealership to double check. Last thing I want is some crap to bite me in the rear when warranty's done on the car and I decide to do something stupid like put a supercharger on the car.

From looking at the live data over OBDII, the engine is running direct injection MOST OF THE TIME. There is a short period after a cold start when it's running the port injectors, but it rapidly switches to direct injection, and you don't even need a scan tool, you can hear the sound of the HPFP when it switches to DI.

In fact, looking at the data stream, I was sure it was going to be the HPFP, because driving at that speed/rpm/load, the only large mechanical change that occurs at the same time as "the sound" is a LARGE and instantaneous increase in injection pressure but as you can see from the oscilloscope traces in the thread I linked above, it definitely isn't the fuel pump.

I didn't do much this weekend as I felt symptoms of a cold coming on saturday, and mostly tried to sleep it off on sunday, but I'm not giving up on the fuel pressure being the trigger:

With 4 knocks per 720 degrees of crank rotation, it could be injection events doing it, rather than pumping events. My next approach will be to scope one direct injector and a knock sensor to see if it lines up.

I guess rattle isn't really the best word, but it definitely sounds metallic, and not a normal souding buzz.

I find that when the sound does happen, and I'm rolling onto the throttle gently the sound is actually louder. However, it is easier to reproduce when jabbing the throttle.