Engine Rattle running 87

Hey guys, I have a 2015 Limited 5.7 with just over 94,000 miles, I purchased the truck with 89,000. Here recently I have noticed cruising at approximately 45-48mph in 6th gear I have a strange engine rattle like sound that appears under very light acceleration. The noise is not loud at all and only can be heard with the radio off and you really have to listen for it, but it is there. I saw someone’s thread on here who had the EXACT same issue and they switched from 87 to 91 octane. I did the same and the noise disappeared. I thought maybe I’d get lucky and it would be gone for good. Filled up with 87 the other day and the noise is back. Has anyone else experienced this? How can it be corrected? I’ve had this truck since November and have already had to have the fuel pump and a wheel bearing replaced. Considering the Truck has less than 100k on it, that scares me. Fortunately I do have a warranty good for 36 months or 3 years. But I know if I bring it to Toyota they will just say “issue could not be replicated” been there a million times… any input is appreciated!

 

I think your are talking about pinging or knocking. I was told that's how you select what octane to use in your vehicles. Start with low octane, and raise a level if there is any pinging/knocking or roughness in the engine. I thinks it's pre-ignition of the fuel.

Good luck

 

Not exactly your same issue but I have noticed much less engine noise since I got the 0w20 out of the engine. I use 5w30 Rotella Gas Truck oil in the winter and 15w40 Rotella T6 in the summer. The difference in engine sound is night and day.

 

That is called detonation, that noise you hear is your piston skirts hitting the cylinder walls.

Caused by low octane gas combusting while the piston is going up on its compression stroke.
Low octane gas will ignite under compression, without spark.
The higher the cylinder pressure is, the higher the octane needs to be for the piston to make a full stroke.
The octane rating numbers don't give you a hotter burn, they are the gasoline ability to withstand pressure, without combusting.
That is why you must use highest octane possible, if you're running boost or high compression pistons
Hope that helps

 

Not sure where you live or where you buy gas, but it could be just crappy fuel. Not all fuel is created equal, and some engines work better with certain fuels. I only run 91 or higher, and only from Costco or Chevron.
My E55 ran like crap on anything but Chevron gas, don't know why, but it was obvious. That car was making a lot of boost and tuned, so it was very sensitive to fuel.
I've been using Costco 91 exclusively in the Tundra and so far so good, no weird noises or detonation.
I will also move to 5w30 oil on the next change as I've heard it makes the engine run/sound smoother.

 

Don’t have a YouTube university degree lol. Truck uses KCLV - knock correction learn value. It’s a long term knock correction. Running 91 and switching to 87 for a tank will knock because it’s probably using the long term from 91. Need to see what KCLV is on 91, then reset ecu and use 87 for a few tanks and see where KCLV is to troubleshoot.

 

Is lower octane fuel the only thing that can cause this?

 

Timing can also cause detonation

 

My '16 has done exactly this on 87 octane. Casual acceleration, transmission upshifts to 6th at 45 mph with torque converter locked, high load at 1200 rpm and it just starts pinging. In my case it was due to trips under 20 minutes and not working it hard enough to get it really hot. It gets very sensitive to poor quality fuel doing that. Big engine never works hard for very long.

Tried 90 octane ethanol free, and 89 and 93 octane E10, and it stopped pinging on all of it. If I ran regular again the pinging came right back by the 2nd tank. Basically I fed it 93 octane for a couple years for safe measure.

Last fall I ran a couple tanks of e85 (mine is a ffv) and it cleaned the carbon out so well it ran several months on straight 87 afterwards and I never heard it ping once. That first tank of ethanol streamed out like seafoam does. All e85 does cloud up some when the engine is cool due to the higher water content produced in the burn but that first tank was filling the lane with fog like a subie on an old head gasket.

The other option is more italian tune ups to burn it out but that's how I wore out the factory tires in 15k miles. Pulling a camper around is a good way to get it worked out.

Driving in S5 under 50 mph is a temp fix I've done before. The mileage difference isn't much by locking out 6th for just that little speed window.

 

Good info, thanks. The KCLV learns faster when run hard. Carbon is a problem, the steam cleaning from E85 or Seafoam definitely seems to help. I do the Italian tune-up, so no issues. Light knocking driving uphill is ok according to owners manual though, no thanks.

*edit* LOL at the deleted post from this thread.

 

If it makes you feel better I have always been to cheap to use 93 in my Lexus. So for the last 180K miles used 87. For the last 180K miles it had the slight pinging you reference, never constant just sporadically under load change. I calculated I saved about $2400 from using 87 vs 93 octane. Just about what the car is now worth. While running I heard countless cars do the same thing. As far as I am concerned its characteristic, don't worry about it.

 

If an engine calls for 91 run it. If it calls for 87, run it. Engines are tuned for a specific octane and running a higher octane in an engine tuned for lower is just burning money. Running lower octane in an engine that calls for higher octane will make it run like crap unless its an engine that the cpu can self adjust for lower octane. The only reason to even run a higher octane than called for is if you cant find the correct octane, ie. Around me there is 87,89,93 and my bike calls for 91, so I run 93.

 

Does the 5.7 demand higher octane? It isn't a high compression motor and I assume there is no supercharger on the OPs truck. 87 should be fine.

https://www.toyotaofbraintree.com/what-octane-fuel-should-i-use/

I don't think the ECU takes as long as some would think to "learn" a different fuel trim from switching octane. In my experience reseting the ECU by the battery method only loses radio settings and doesn't help your ECU. If anything I would try 87 from a different station. Sometimes you just get bad gas.

 

On the side of your engine is a knock sensor. Once it senses predentination/pinging (vibration) it sends a signal to the pcm to automatically retards timing. That is why you don't hear the pinging all the time, the ECM retards the timing until vibration dissipates then advances timing again in the quest for fuel economy. I don't think this is any learning.

 

87 is the minimum octane.

I run 87 in dead of winter. Then run 88 or higher during warmer months.

 

Could you say more about how temperature affects knock, please?

 

A very high level explanation:

Higher ambient temps will increase air/fuel mixture temp. Once the engine cycle is at point of ignition the final compression state will add more heat on top of that.

this can put the mixture at point of pre ignition. This is a technical point of pressure and temperature where the mixture self ignites just before the spark ignites.

the sound heard is two flame fronts colliding. In severe cases yes it will make mechanical noise from piston to wall contact, etc.

so there are also degrees of severity as well from minor to a full on death wave going through the engine.

there are other factors involved but a simple increase in octane level is a super easy and relatively cheap thing to do.

 

there are a bagillion variables that can technically cause it.

Off the top of my head

compression ratio

Octane rating
Intake air temp (ambient temp plus heat soak)
base timing
timing map
a/f ratio, too lean or too rich.
Spark plug design (porcelain surface area, depth of spark plug)

VE (volumetric efficiency)...too low like mentioned in this thread: low rpm at low vehicle speed. This one variable is contingent and another set of variables like gearing, transmission mapping, cam timing, cylinder head design, etc...

Large swings in VE (tip in conditions)
Engine blow by (if your engine gulps a lot of oil it lowers your octane rating)
Generalized carbon contamination of intake valves and piston tops
Cam timing swings
Camshaft design
Cylinder bore size... larger bore diameters are more prone to pre ignition
Cylinder head material.. heat transfer rate
Engine block material... heat transfer rate
Piston design and material.
Combustion chamber design for squish, quench, swirl, tumble.

 

What does the manual call for? Anything greater is a waste. In a car like my 1970 396 which REQUIRES higher octane ethanol free gas using less will cause the issue you refer to. Ethanol free gas of the same octane will also work better but mess up your converter!

Same kind of arguement can be made as to why change the oil sooner when Toyota requires it at 10K

 

I’ve switched stations numerous times. The only thing that will get rid of it is 93.

 

My 2021 Crewmax works fine under all conditions with 87.

 

Even with only ~2400 miles on my 2020 I notice the engine runs smoother with 93 octane and a recent oil change to Amsoil signature series 5w30.

First I noticed the bumb from 87 to 91 smoothed things out a bit, so I just use 93 like my other cars. After the oil change the engine seemed to smooth out a point or two more, especially on start up.

 

Where in the owners manual do you see that light knocking is ok driving uphill?

 

There are a lot of factors besides compression ratio that determine the necessary octane. In addition to the engine construction, environmental factors also affect octane requirements, primarily heat and load. The 3UR has a compression ratio of 10.2:1 which generically/historically speaking is high enough to warrant 91+.

For me the sticking point is that the LandCruiser and LX570 both require 91 and tuners have shown that the Tundra will advance timing when running 93 octane. Also from personal experience with my truck and others with similar experience, higher octane does make a noticeable difference in how the engine sounds and runs.

87 will work just fine and not cause any problems as the ECU is smart enough to protect the engine and Toyota says its fine too. Run whatever you are comfortable with, this is honestly a lot like the threads on which engine oil is best. Just buy fresh quality gas and you'll be fine.

 

I run 86 no issues here