So, my girl has always had a wee bit of pinging in 4th gear. Generally it only happens when we start to gently hit an incline and so I always practiced giving the pedal a pick to force her to downshift. It does fully go away with premium gas.

Fast forward to yesterday; I'm driving down the highway and come up upon a very small incline and LORD she was pinging like I've never heard. So much that it was extremely alarming. Best I can describe it would be if you had a cup of steel washers and shook the hell out of it. I won't lie, I literally thought she was blowing up right then and there. But I tapped the brake to cut the cruise and it stopped as we began to slow down.
I decided to give her a decent bit of gas to force a downshift, as she went from low rpm's to higher rpm's I heard the pinging again just for a moment till she reached like 2200-2300 rpm's. I turned off overdrive to keep the RPM's up and drove carefully till I reached my destination. No pinging with overdrive off.

After that, when I was driving home she was mysteriously fine for 70% of the trip but even when she pinged it was never super loud again. When I got back to town I was at 1/4 of a tank so I filled up with premium. While driving to the house, under no situation could I get her to ping at all. Now, as mentioned before I was already aware of this before but I've heard some guys say the 3.4 is going to ping a little.

So, I don't have an issue putting in premium but obviously something is wrong and I'm really afraid for my girl.

Now, I will say I'm maybe... 1000-2000 miles away from the 25,000 interval for spark plugs, but the last time I mistakenly went over 25,000 miles she had "drive line kicks" going up hill. Instantly solved with fresh plugs. Now, I'm waiting for decent weather so I can change them again but I am worried it is something other than the plugs. No idea if it matters but the tank before premium I got about 19.2 mpg. I would presume fuel economy would drop if something was out of whack but maybe not?

Any thoughts or ideas?

2000 4Runner, V6, 195,000 miles.

When was the last time you ran some good quality injector cleaner?

When you pull the plugs and shine a light into the cylinders are the piston tops black from carbon or do you see aluminum?

Carbon buildup will cause pinging and our engines don’t monitor and prevent knock until 3000rpms

If you pull your plugs do all of them have the same color?

Is one or two lighter than the rest?

To me either got carbon buildup or a cylinder or more leaning out.


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Injectors dirty or really low octane fuel. As possibility of the issues.

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I haven't ran seafoam in a while but the injectors were actually replaced like 2 years ago. Although I guess it wouldn't hurt to run some seafoam or something huh? I'm going to try to pull the plugs this weekend to replace them so I'll take a look. Should I be able to see the top of the cylinder? I always figured it would be two black the too see anything.

Yeah I wasn't thinking about the injectors since they were replaced 2 years ago, but yeah I guess it wouldn't hurt to run some seafoam. I just wouldn't expect it to get this bad this easily

I’m a techron fan or amszoil fan or a redlion fan over seafoam.

Shine a bright flashlight in the spark tube holes.

A borescope kit for a cellphone or tablet is cheep and will get you inside. They are also one of the best things to use to find head gasket leaks


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I'll have to check those other products out. Hmm, I never thought about a borescope. But either with that or a flashlight, what exactly am I looking for? Like if it's jet black that's a problem?

Compression test should rule out head gasket leak. I really think you had junk fuel.

Especially all the sudden like that...

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You are looking for carbon buildup on the piston top. It raises compression and also creates hot spots that can cause pinging.


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I've been wanting to do one but have been waiting for the right weather along with combining it with the spark plug swap.

I pretty much always get fuel at the same two gas stations, I mean maybe they had a bad batch in? Like I was saying I've always had some hanging that did go away with premium so this must have been pre-existing. Maybe...

Well dang. Is that what the different cleaners and stuff are supposed to get rid of?

Sucking seafoam or an upper engine cleaner through a vacuum line will help get rid of carbon deposits as well as a good injector cleaner.


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I know the name sounds sketchy yet I've run startron enzyme fuel additive for years on small engines and autos alike.

I've removed spark plugs after thousands of miles and the additive appears to make the ignition hot, no carbon remains on plugs or inside piston area.

I began using it only for its alcohol treatment properties on small engines then noticed the affect so expanded its use. Luck all.

https://www.amazon.com/dp/B00D3IEIY0...el%2Baddi&th=1

A healthy 5VZ-FE should never ping. Gas might be a part of it but you should be able to run 87 octane and charge up whatever hill you want without any problems. Spark plugs are relatively good and injectors are new. I'd rule those two out. How about the fuel filter? If clogged it can starve the engine of the fuel pressure it needs.

If the engine is cutting gobs of fuel with a bad MAF reading that could also cause it to run lean. Do you have a DENSO MAF sensor and has it been cleaned lately? Air filter replaced every 12 months?

If those two items are good then I agree with carbon buildup on the pistons. Seafoam through the intake (check out the Seafoam Spray for easier application) should make a considerable difference if that indeed is the problem. Plus it's a lot of fun do to! May foul your O2 sensors though, it did on mine.

OP, do you have a scanner that reads live data? If so, what is your LTFT?

For carbon removal I use a GM product called upper engine cleaner in a spray can or water injection.

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You happen to have a video of it, or any way you could snag one at some point? I either have something loose or just developed the EXACT same problem... the second I hit 65-70 it kinda sounds like jingling washers, but it's also a little too rhythmic and too located to one corner to be pinging. I'm curious what your engine sounds like for comparison

I'm not mechanically savvy enough to call what I had, pinging vs knocking?

But I had a sudden onset motor noise event a couple years ago.

96, 3.4 V6.

In the mountains for the weekend, fine when I parked, noisy when I started it up.

4 hour drive, early Sunday morning, nervous and irritable.

It stopped after maybe 15 miles, seemed fine for the rest of the drive.

Week or so later, big bang under the hood, super noisy, ran like crap but I got home.

Spark plug came loose and blew itself right through the coil pack.

My awesome local garage heli coiled it, and found another loose plug. Snugged everything, replaced a coil pack, been fine since.

They're working theory was a little bit of gunk fell down in when the thing cracked loose originally, and caused the noise.

No proof of course, but she's been fine ever since.

So if ya haven't already. put a socket wrench on those suckers just to be sure.