Buzzy Vibration at certain RPM's..read before buying!

Toyota got me fucked!

Toyota field rep scheduled to test drive one of their truck with me 2x's but it didn't go through because they couldn't come out. They then promised me that today will be the day they will come out for sure. Well, just heard back from the dealer that they have made a conclusion not to come out anymore and going to stand behind their tech believing it's normal. Had me took in my truck first for wheel balance and second for road force balance (everything was within spec). Took today off (lost $200.00 work pay) to tell me they will not be coming out anymore plus they don't have a truck available. Mother fucker could've said no at the beginning!

 

That's Toyota's response to you:

 

Similar story with GM...

http://www.autoguide.com/auto-news/...suvs-and-no-one-seems-to-have-a-solution.html

Seriously, somebody needs to get some press interested... though the problem is many (most?) are paid off by manufacturers.

 

Well guys, I just got my 2wd DCSB Sport back from the 4th dealer and the vibration everyone is describing STILL exists! This dealer tried replacing one tire, but it didn't solve the problem. I too have been told by other dealers that Toyota says it is within normal operation. I now have over 10K miles on the truck and there has been no change in the problem. Just had the service bulletin upgrade to solve bucking and gear roaming issue, so we'll see how that works out. Love my Taco but hate this problem. Have been waiting to customize it until this bug is worked out - don't want to put good money after bad. A suggested, I just contacted the consumer reporter at the local station in the Tampa Bay area. We'll see if I get a bite.

 

Oh, and forgot to mention - I get worse highway mileage than in the city - seem weird to you? Anyone else notice this?

 

My truck never seemed to have this issue much other than 5th gear at the RPM range where it occurs, for me that was 2100-maybe 3000 or so.
My vibration has all but vanished after I installed sumosprings. I also adjusted the exhaust hanger right by the axle while down there. I also wondered if maybe when I put the U bolt, uh...plates?, back on maybe I moved them somehow. Regardless my vibes are non existent at this point.
The sumosprings were not installed for any reason to do with this issue, just the normal reasons for them.

 

3200 miles later and is a non issue. sucks toyota wont do this but for everyone else crying the blues, missing days at work and wasting time on the phone with corporate i suggest you take matters into your own hands.do a search of my posts to see all the pics and my repair. post #2343 the root cause of the vibes will probably never be rectified but you can certainly make your driving experience more tolerable. now i only hate the auto trans and the seat/headrest!!

 

Okay Guy's new poster here with a 2016 vibrating Tacoma. 25000 miles and it's annoying. I read about 50 posts here today and I agree that it's possible that it may be exhaust related. I'm 63 years old and been a Porsche,BMW (master tech) Mercedes and VW mechanic. I currently have a full shop at my house and repair old air cooled 911's. I too complained to the Toyota dealer and reps wit no joy. I'm thinking of welding in a couple of stainless flex pipes (like the front pipes in transverse mounted engines) in line with the exhaust. I'll keep you posted.

 

Thank you! Finally a right dude to do that. I kept suggesting doing it repeatedly.

 

I have a Sport with no vibration. Cruise control is made for flat & dry roads. Who doesn't know that?

 

I too experienced "the vibration" while test driving a 2017 Taco a couple weeks back (2WD DCSB V6 slushbox, I do not remember the exact trim but it was more or less equal to my '09 DCSB SR5 TRD-Sport. The general sluggishness and hunting transmission (as compared to the 4.0/750E combination) pretty much turned me off so I did not pay as whole lot of attention to the 5th/6th gear vibrations, but it was noticeable¹. I had a theory on this which I will get to below.

I had seen this thread previously however my chronic insomnia caught up with me last night and I read the whole thing, all 119 pages, 2374 posts--so here goes:

The 3.5 L V6 claims to be a dual mode Otto/"Atkinson" -cycle engine; however it is not a true Atkinson-cycle engine and calling it one will not make it so (see the Wiki article's Modern Atkinson-cycle engines section.) What it is is a plain ol' Otto-cycle engine that through the marvels of modern variable valve timing has the ability to hold the intake valve open well past BDC of the intake stroke; thus achieving in a counter-intuitive manner a "sort of" Atkinson-cycle. But in reality what is being done is that a portion of the intake air charge is actually being ejected back into the manifold during the extended time the intake valve is open.

Here is the valve timing for the "Atkinson-cycle" as as published in Toyota's 2GR-FKS New Features document; the intake valve stays open for 105° after BDC on the intake stroke; notice that it also opens rather late at 33° after TDC

Note the "At Partial Load" qualification--which coordinates with the circumstances under which the vibrations are most egregious:


What happens is that with the late opening a lesser air charge (just air, in this mode fuel is directly injected into the cylinder near the top of the compression stroke) is drawn in, and with the very late closing a portion of that lesser charge is blown back out into the manifold.

With less air to compress, and the piston being more than half way "up" the cylinder by the time the intake valve closes the compression ratio is lowered and the engine becomes less powerful but more "efficient"--not really but it uses less fuel.

Per my "back-of-a-napkin" calculations it takes 25 to 35 HP (a partial load) to keep a Tacoma moving at a steady 60 to 70 mph, which will be a larger "chunk" of the now less powerful "Atkinson-cycle" engine's potential output. So as long as it stays in the "Atkinson" mode the engine will be working harder--and vibrating more--sort of like the way an engine being "lugged" at an inappropriately low rpm while in the "wrong" gear vibrates.

As was mentioned several times in the thread Prius owners have been quite vocal about unacceptable vibration with the "Atkinson-cycle" engines, and Lexus moved to more sophisticated engine and other mounts I suspect to dampen the what I believe to be inherent increased engine vibration. In doing this research I also found that Honda owners are reporting similar issues with their "Atkinson-cycle" engines.

It is also worth comment that a Lexus being more aerodynamic than a Tacoma (they really are) is likely to require a smaller percentage of the 3.5 L engine's reduced output while in the "Atkinson" mode.

So in the end it would seem to be "normal" and "as designed" due to the (IMHO) silly goal of improving fuel economy in a truck by fitting it with a too small³ and overly complex engine. As the whole "Atkinson" thing is controlled by the ECU it would be interesting to disable it and see how things go.

There's my 2¢ worth--doesn't really matter to me as both I and my '09 likely have just another 12 to 15 years left in us--so I'll never own one anyway...

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¹ - FWIW my '09--"certified" with all recalls, TSBs, etc. verified/performed last October--runs/drives as smoothly as anyone could ask; no vibrations, clunks, nada.

² - Air has mass and therefore inertia, this is why intake valves normally close a bit after BDC on the intake stroke. The air charge's inertia want it to keep moving and even though the piston is now moving upward in the cylinder the inertia of the mass jams a bit more of it into the cylinder. This is about as close to "ram-air effect" as you will see in a land vehicle.

³ - All other things being equal "there is no replacement for displacement"

 

Great write-up. Thanks. This was the explanation given to me as well as engine/ trans mounts. Since the 2.7 does not do this it seems to confirm this theory.

 

It is unfortunate that the government mandates (emissions and CAFE requirements) have forced manufacturers to sacrifice driveability for the holy grail of fuel economy. The irony here is that in my "retirement" driving (75% rural 65 to 75 mph, 20% suburban (35 to 45 mph), and 5% "in-town") I get a quite consistent 19 mpg from my '09 4.0 DCSB--and I see real-life mpg numbers from 3.5 V6 drivers of 18 mpg.

My wife, hardly an "enthusiast" ny any measure, drove a 2017 HIghlander under pressure from the local Toyota dealer while there for a transmission flush. She told me it "did not have any power and shifted too much". She has a 2003 with the 3.0 L V6 and a 4-speed slushbox with 235k miles on it. She often describes it as "the best car I've ever owned"...

 

Good writeup, well thought out and presented. I'll have to disagree on one of your main points though:

While it is certainly possible that the pseudo-Atkinson cycle could cause increased vibrations at partial load (as per your explanation), this does not explain why these same vibrations become more pronounced when in OTTO mode.
An example:

While cruising along a flat highway at a constant speed within the dreaded RPM range for this vibration (approx 1800 -2200), you'll be buzzing - and in Atkinson mode. Now push the gas to 3/4 or even WOT. The engine "should" have switched to OTTO mode, as the load has increased substantially. Well, I can tell you the buzzing becomes quite a bit more pronounced, until of course your RPM rises out of the said range. Note that I have a M/T, so no downshifting in this example. And yes, it will accelerate in 6th gear if you do this!

My .02

Frank

 

I have been unable to find any specifics as to what conditions bring on or cancel the "Atkinson" mode; except that it is load related. However I do know from my tuning experience with "fly-by-wire" throttle Mustangs that conventional thinking re: pushing "the gas" and "3/4 or even WOT" are no longer relevant. The ECM reads the accelerator pedal rate of change and position to determine what the driver would like to have happen, and then it decides what really is going to happen.

It reminds me of the old military recruitment ads claiming one could choose what they wanted to do upon enlistment. You could. And then once you completed basic they would tell you what you are really going to do.

As I alluded to in my previous post I would bet money that the worst of it could be tuned out--but I suspect that were that done to attain optimal driveability any benefit of the silly "Atkinson-cycle" mode would evaporate. Also any significant change to the tune, such as this, would require Toyota to go through the whole EPA/whatever certification again--that as I understand is not an inexpensive or fast-forward endeavor.

Ten+ years ago I authored Mustang tuning software for a well-known house in Florida. For anyone in a "smog" state we told them "1) Flash the stock tune; 2) Reset P1000 or disconnect the battery for 5-7 minutes; and 3) Drive 100 to 150 miles before getting it tested." otherwise it will fail...

 

The independent engineer / master tech 30 + years I hired came to this conclusion: engine "rubber" trans mounts / engine cycles between otto/atkinson. Looked at Lexus -- same engine--uses hydraulic engine mounts....not compatible with Taco.

 

Is it just me, or do all these threads on Tacoma World make everybody hypersensitive to any vehicle their in.

I can't drive anything without picking up sounds or vibrations that others have never noticed.

There's probably a medical term for it...

 

Many of us here notice this vibration on long trips...for me it's after an hour on the road.....I drive 500 miles per week.

 

Oh no, I'm not questioning any of the vibration claims. Just whatever vehicle I'm in lately, I seem to pick up on even the lightest vib/ noise.