How bad is predetonation/pinging/spark knock for your engine?

I’m running 87 from quick trip and it is scorching hot out here in Georgia at the moment. When I apply light throttle and the truck downshifts, I can hear it ping for a second or so. Same thing happens when I let off of the throttle, every time. I will swap up to 89 when this tank runs out but it’s a brand new tank so it’ll be a while. Any concern of causing damage? I see the owners manual described this as normal. Thanks.

 

If it's detonation that can cause major engine damage if left unintended i.e. holes in pistons. The knock sensor should detect this and retard timing. Detonation will not occur on decel. so you might have another issue. These vehicles are designed to run on 87. One tank should not do any harm.

 

It’s weird. It’s low RPMs with moderate load, I can hear it ping either downshifting to a lower gear or lifting off of the skinny pedal

 

It is in your head. There is nothing wrong with running 87. You are wasting your money buying 89.

 

Is the CEL on or any codes?

 

What you described is 100% not detonation.

I will say though my truck is a bit less lethargic when I run 93. Especially when it's really hot out.

 

Completely normal. Some trucks seem more predisposed to this “issue” than others. I will counter a previous poster and tell you premium is NOT a complete waste of money. Perhaps it’s frivolous, but that’s a matter of your opinion. The pinging you describe may not adversely affect the health of the engine but this extra knock absolutely can and will affect how the engine decides to run (ie the computer will initiate timing and other changes to compensate). If you don’t feel like it’s negatively affecting the driving characteristics and you don’t mind the occasional pinging, then 87 is just fine. If you feel like it’s causing hesitation or other annoying qualities, then a higher octane absolutely can make a difference.

 

I posted a month or so ago with almost the same experience. I noticed you said it was scorching hot out, does anyone know if hot weather contributes to this or just in my head. It seems my truck does this more in the hot weather also

 

No codes, no CEL, just during changes in throttle I can hear a few little “tinks” or “pings.” I can hear the standard injector noises in the cab and now just the little pings on changes in throttle. Still runs great just a weird noise. Gave it a good full throttle 0-90 on the ramp and still loved it like normal.

 

My Tacoma has done this since the day I drove it off the lot. It knocks when I let off the gas between 1800 and 2500 rpm in hot weather or the A/C has been running for a while. Higher octane = less knocking, but it can knock on 93 octane! I'm running 89 octane right now because of the weather. Unleaded 88 (E15), which is cheaper than 87 and provides about the same fuel economy, is a good compromise.

My hypotheses are:

1. The engine momentarily goes lean due to opening the throttle while transitioning from Otto to Atkinson as load is reduced, causing detonation. Or,
   
2. Under load, cylinder temps go up. When Atkinson mode is engaged after a period of high load, the intake air has extra dwell time because some of it is pushed back into the intake. During this time, it absorbs more heat, resulting in a hotter mixture and detonation.

A/T owners hear it when the truck is shifting gears because the ECU modulates power to assist the transmission, such as by cutting power during an upshift.

 

Funny I heard it today also

 

Seems as if everyone's truck does it, even more commonly on the 4.0. If nobody has any reports of damage from it, I'm not too worried about it. Thanks!

 

Help me understand how pre-ignition/pinging/pre-detonation is occurring off-throttle.

 

At least it's not dieseling

 

they're probably hearing the differences in the system switching from direct to port injection...

 

Nope, not directly, although switching back to port injection might be exacerbating the issue.

 

Atkinson mode, or rather the transition between Otto to Atkinson modes.