Piston Slap: Detonating the Need for Premium Fuel?

Toyota

Adam writes:

Hello, I’m writing in hopes that you can help me find an answer. I bought my 2021 Tacoma (3.5-liter V-6) new and now have approximately 50,000 miles on it. The issue I have is during the warmer months when I am in a low RPM/high load situation. Before the truck downshifts to a lower gear, the engine will ping.

I have only noticed this happening this summer. Now that it has gotten cold here in Wisconsin it has stopped. I talked to my local Toyota dealer and was told little more than a “yeah, you might have to run premium in the summer.”

I have put in 93 octane and the pinging did stop. My question is, why? The 3.5-liter is a dual-injection engine, and the port fuel injection should eliminate any pre-ignition. Nowhere in the owner’s manual does it stress the need for premium fuel. The truck will be out of powertrain warranty soon and I’m trying to resolve this issue now. Any thoughts would be appreciated.

Sajeev answers:

You are right, Adam. This type of engine detonation should not be happening on a 2GR-FKS engine in a Toyota product. As you noted, this engine has both direct and port fuel injection, which should wash away the carbon-building sins of direct injection.

And quite frankly I am stunned to hear it’s happening on a 4-5 year old example with 50,000 miles. But maybe that low(ish) mileage is part of the problem? I see two possible issues to resolve here.

The first is to avoid short trips where the engine doesn’t get up to operating temperature, as gasoline doesn’t vaporize as well when cold. The unburned fuel can lead to carbon deposits, but I am not sure this is the issue here.

At least it’s not the main issue: Perhaps you need to buy gasoline from another station or try another brand. The “Top-Tier” fuel vendors are promoted as having more additives than what’s mandated by the government, which should help remove carbon buildup from the valves. Considering how minor the issue is (only under load at low RPMs) in your Tacoma, maybe a fuel quality issue is the most likely culprit?

I’d recommend two courses of action: switch to a top-tier fuel for 1-3 tanks, or do a de-carboning treatment either in a can or via local service. Or maybe both, but I recommend starting with better-quality gasoline first.

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Comments

    I agree that there is a lot of “junk fuel” out there, and often buying based on price alone is luring us into using inferior gas. I think it makes sense to try a few tanksful and see if it cures the pinging before trying any decarbonizing treatments.

    I often wondered what exactly makes gasoline “Top Tier”. Have read, wish I documented the source, that all gas comes from the same refineries regardless of brand. Tanker driver adds extra detergents prior to transferring to in ground tank. If the weather is nasty this may or may not be done. Also lower price gas may be older.
    Has anyone seen any studies that independently verify gasoline quality at the pump?

    Top Tier is a standard of fuel set by several auto mfgs. To get this rating you must apply and they will test to see if it meets this standard.

    The additive package is what is added you are correct there. But it is added no matter the weather. Standards are tested and met if not they could be in trouble for not selling what is promised.

    Same on oil standards like Dexos oils.

    Auto mfgs today need specific packages to make sure fuels do not carbon or oils will not break down since they do more than lube today.

    The additives are added when the fuel is added to the tanker, not just before transferring to the in-ground tank at the station. As hyperv6 has stated, this is verified by TopTier® by an unannounced audit. Whatever site you read was probably propaganda from someone affiliated with a non-TopTier® gas station or brand. 😆

    I was a tanker driver for Sun Oil Co. and the extra additives were done at the refinery, not by the tanker driver.

    Carbon builds up eventually over time in all engines mainly because of the impurities of reformulated gasoline. Top tier fuels will prolong the process but not eliminate it as the main difference with these fuels are more of the detergents and cleaners needed to actually do the job which is why they are more money. (You don’t get something for nothing with oil companies). When enough buildup occurs this effectively raises the compression ratio requiring the need for higher octane. A high quality fuel service using equipment to clean throttle body, intake manifold, and combustion chamber will restore the need for regular fuel. Most people don’t realize this is happening until the symptoms of pre-ignition are present and by that time a tank additive generally is not enough. There are all kinds of snake oil out there with no industry standards to regulate good from bad. I have found for over thirty years that BG Products made in the USA to be very effective in this application. Just sayin.

    It used to be carbon was mostly due to oil getting past rings and seals. But today the advent of Direct injection is making carbon. build up on the intake valves and ports since there is no gas to clean them flowing by. All valve stems bleed a little oil and now they took away the fuel to clean it.

    Companied are addressing this in different ways but some are not working as well. So more cars today may need a professional cleaning of carbon earlier than in the past.

    Techron is not a snake oil and is recognized as an accepted cleaner by MFGs. but the question is how bad is this on this truck and is it carbon.

    My 2002 Corvette (60K miles) fuel gauge stopped working so I added 16 oz. of Techron in the fuel tank and the fuel sending unit started sending the correct information to the gauge again. Techron works great in my opinion.

    Maybe the OP just needs to perform a “polish tune-up”. I remember a friend – a mechanic- years ago bought a brand new Ford Camper Special with the 360, 3 speed with overdrive. He said he was never going to rev it over 2200 RPM and it was going to “last forever”. I told him he would ruin his engine. In less than 6 months he had to switch to premium to eliminate ping, and in less than a year he had valve leakage issues due to carbon buildup. Warranty (he JUST snuck in) did the first valve job. Less than a year later he did the second one and after the third one finally agreed he had to DRIVE the sucker!! Just a good FULL THROTTLE high speed pass every once in a while eliminated his problems. ( he was driving from Waterloo Ont to Winnipeg Manitoba and back without revving over 2200 RPM if you can imagine!!!! – North of Superior if any of you have ever driven that route -_-)

    That’s been called an “Italian tune up” for as long as I can remember (and I’m old). It refers to the way Italians have historically been known to drive— flat out.

    It sounds like you are saying that TopTier® gas is not good enough to maintain clean engines, yet the detergents in the carbon-cleaning kits are. I don’t think there is enough real data to support or refute that claim.

    It is best to add Techron to your fuel as it is an approved cleaner by most mfgs. It can restore injectors and help clean carbon. Do not over use it. More is not better read the instructions.

    I’m not a snake oil guy but this stuff works. Corvette guys restore fuel level units with it when they get varnished.

    Might check Nox sensors too. Could be bad. But Carbon is likely.

    If it continues you may need them to do a professional cleaning.

    Some mfgs have more carbon issues than others due to Direct Injection. GM over laps the valve timing now to get some fuel on the intake valve. Others have varied systems.

    Yes, Techron worked on my 2002 Corvette fuel sending unit. Saved me from having to remove the sending unit from the tank to clean it.

    The possibility exists that there is an operating condition during the summer that the Toyota engineers did not anticipate. If the Toyota dealer is saying to run super in the summer, I would run super in the summer. The only real alternatives are computer retuning or going internal to the engine

    We use Citgo regular, a top tier fuel. For Toyota products : We have 1 Tacoma, and 3 Lexus RX350 that call for premium. Never use it. We do use twice a year Techtron, with no more than 10 gallons in the tank. No issues with any vehicle

    Change the gas first. If that isn’t cutting it, try a fuel system cleaner with techron (Chevron brand name but it’s the best out there.) If none of that solves it, consider changing to a low calcium oil which can reduce low speed pre ignition (LSPI) which can help as well.

    I’m surprised that modern software can’t resolve this. How is the knock sensor not commanding the ECU to pull timing when it detects pre-ignition?

    On my 2012 Subaru Legacy I would get horrible pinging at certain engine loads when running 87 octane from our local mega-carwash gas station that was on my way to work and had the lowest gas prices in town. Sunoco and Valero 87 octane (via a slight detour on the morning commute) would be fine, no pinging. I adjusted my gas station visiting habits and that kept it at bay until I got rid of the car.

    A significant clue, pinging is pronounced in summer, opens the door to other root causes besides carbon deposits, which are not seasonal. Warm air is not as dense as cold air so MAF or another fuel injection system sensor near or out of tolerance limits is where I’d begin. Somewhere there’s a scan tool ready to reveal root cause(s).

    I bought a bottle of dollar store generic ‘Fuel Injector’ cleaner. Not that I had any intent what so ever of using it in anything I own, just out of curiosity. Thought it would probably be a bottle of nail polish remover (acetone) that might work as a degreaser at best. Smelled like burnt cabbage or something. Made by somebody somewhere and bi-product of a bi-product I’m guessing. Also bought a new bottle of Shell X-100 ‘classic’ not that long ago, just because it was so 50s retro looking except for the cap. God knows what’s actually in it.

    I’m curious why you bought the product. Did you have plans to have it tested? Now that you own it, is it just going to sit on your shelf?

    I’ve driven all merits of turbo charged cars from late 70s 80s and 90s. Low boost 3-5 psi and all required premium. From early bosch mechanical injection to finally electronic mulitport. Carbon on the valves was not too much of an issue but predetonation was. Its interesting that your vehicle has started doing this at 50K. Although gas these days is pretty much manufactured by anyone and its only the additive package that goes into it for the name brands. I’m wondering if you fuel your using is not up to it. Never use 87 and honestly even for the 50-75cent difference in cost sticking to premium will eventually fit your budget without noticing. 5-12 bucks more over a ruined engine may not be worth it.Using additives may help like MM oil or Lucas or some sythetic 2stoke. I’ve used them all in the past with varying success. I would pull your plugs and scope your bores and look and the top of you pistons for exessive carbon buildup. The new issue with dual injector setup is the pre-injectors before the valves sit idle during long drives and get hot from not flowing fuel through them. Build up eventually happens and thier pattern goes from a fine mist to a stream like spray. That ineffecient spray pattern can carbon up your valve and piston crown. I’d run cleaner twice a month till it clears and then once a month.

    The time of the year should not affect the gas it needs. If they recommend 91 and above use it all the time. I would go by what the manual says. Part of me thinks that engine wants 87 from what I remember. In my area Costco and QuickTrip gas stations are top tier so I always go to them. The question is where are we getting gas here first. One could also add a can of SeaFoam to the tank of gas and see if it helps also.

    Time of year has 3 effects. Winter vs summer gas, operating temperature, and air density due to intake air temp. Hot engine/warm intake air can aggravate ping. Highly reformulated/”contaminated” summer fuel can behave strangely.

    I used 5 cans of Seafoam in 5 tank fills in my 73 MGB due to a pinging problem as it was the last thing I could before taking eh head off. I did all the timing, tune ups, plugs, wires, coil and carb adjustments with no positive results. Same with the Seafoam. I was going to try Marvel’s Mystery oil but decided to put 15 litres of 100 low lead aviation fuel in with 35 litres of 93 octane Shell. Voila. No more pinging. After running about 50 L of 100 LL aviation fuel over about 1000 miles the car ran very well on its normal feed of 93 octane.

    In cold climate areas the gasoline produced in winter has more dissolved gasses such as presumably butane and propane. This gasoline has relatively low energy compared to summer gasoline where the dissolved gasses are present in smaller amounts. This will presumably affect the ignition performance. I certainly note in the spring when we switch to summer gasoline when we get better gas mileage (not just the temperature effect). The gasses are added to improve ignition in cold winter climates and as a relatively cheap additive that cannnot be added in the same amounts in summer gasoline because of the higher temperatures.

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