Hey all. The entire time I owned this truck I noticed the engine sounded like it had the smallest amount of lope when RPMs were real low - not enough to be concerning, just enough to barely notice if you really paid attention and traffic was light enough - and in my research I read that our cam profiles are pretty aggressive for what they are (the same culprit behind all the power being used up by 3000rpm), so I always chalked it up to that and let it keep on ticking. If anything it sounded kinda badass

However over the past week or two the noise increased drastically out of nowhere to the point it can be heard over traffic. With your hand anywhere in the engine bay while idling you can definitely feel the pulses clear as day. The strange thing is it only occurs while the engine is warmed up, and ONLY happens in drive. When the trans is in neutral, park or reverse it idles smooth as glass. In both situations the car will idle smoothly at 600rpm - tach doesn't fluctuate, bounce around or do anything weird. No codes currently, but I did throw a P0420 the other day (which I suspect is for a dirty O2 sensor.) When throttle is applied in drive the sound seems to go away, but it's very difficult to tell as I have both a driveline vibration and a mysterious howl going on too :/

I recorded a quick video here that captured the sound really well (personally I can hear it better with ear buds). At this current time it was pretty loudest and harshest it's been yet, but it seems to vary in severity every time I come to a stop (and very conveniently gets super quiet whenever I finally get home.) Sounds like a Cummins with an oversized exhaust is constantly idling next to me.

Anyone have a clue what it could be or knows what disengages/alters when the engine is free of load?? I assume those would be the next components to look at, but I can't think of what that would be aside from trans and torque converter? I was thinking maybe a valve adjustment was in order as I'm certainly due for one, but the fact it's only present in drive throws me for a loop - and similarly, I've never heard a transmission or torque converter "chop" before... I've looked around the engine bay and tried the ratchet extension "stethoscope" trick to try and locate it but the best I could deduce is it was stronger on the passenger side of the vehicle (and even that was a little questionable.) I checked for exhaust an leak as well but everything looks/smells just fine. Spark plugs, coil packs, and fuel filter were changed out maybe 20-30k miles ago. Just changed the oil last Saturday and gave it another check this afternoon (looked totally normal in both cases.) Timing belt and whatnot was changed before I got the vehicle but I've yet to do so, fwiw.

Edit: I found some people posting about a "cam sub gear" falling out of adjustment and/or the spring losing tension, and some people posting about bad valve seats, but I'd think those would be audible all the time, even in neutral right? I just checked fuel trims and for pending codes for giggles, no codes pending and fuel trims were at 0.0% ST and 0.8% LT.

Just a thought could be wrong. 2 things come to mind.

1] If in the window for valve adjustment or check. I would do that as those out of adjustment are known for loud ticking.. This will it as when warmed up, your idle drops to around 600 or so sitting in drive.

Being it's not a constant tick and sounding like it's coming from the bell housing kinda rules out the flex plate cracking and making noise. So that kinda rules out that one.

On the valve adjustment check. I would just get the valves in the good clearance range. If you try to make them perfect. Not only will you drive yourself insane. You will have your rig down for weeks.

A final thought would be a louder injector. Those buggers sometimes get noisy. However, you should be able to pick that up with listening next on them as well.

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That just sounds like a misfire. I had another old Toyota that sounded like that when I got it. Found out the spark plug in one of the cylinders was destroyed and I was running of 5 cylinders. Before I knew that I just bumped up the idle speed as it ran a lot better at 800 RPM than it did at 600 RPM just like yours is doing.

Do a full tune up of maintenance items in the engine bay before trying something like a valve adjustment. Those are not for the faint of heart and will test your patience like no other job on these 4Runners. Tune up would be:

• Replace air filter
• Clean Mass Air Flow sensor with MAF cleaner
• Replace spark plugs if mileage unknown
• Replace spark plug wires
• Run a quality injector cleaner through the tank (I recommend AMSOIL or Royal Purple)

All of these are things you'd be doing normally and none of it will break the bank or take too much time.

Oh I'm well aware of how shitty of a job it is, it's something I've desperately wanted to avoid in any way i could
My injectors are original... Is there any way to test them? Outside of a machine of course, i mean like applying voltage or checking continuity or something. I'm not opposed to replacing them, I was actually looking into those upgraded ones from Yota1 or whoever it was not too long ago. Not higher CCs; the ones with that supposedly atomize way better from multiple ports instead of singular
It's ironic, I'm a cylinder head tech myself but I'm totally useless here as I work in diesel and it's a totally different animal
Guess I could check spark plugs this weekend too. The reason I believe my O2 sensor is dirty is because there was quite a bit of soot at the tailpipe from me just running some injector cleaner, which is something I had happen in 2021 at some point - going down that trail there's probably a chance the spark plugs (replaced in 2020 or early 2021, before the first o2 code) are all sooty and carboned up as well. Hell, maybe that's what dirtied up the sensor in the first place
All other things mentioned have been done within the past 6 months or so (except coil packs)
Edit: been watching some videos of misfires, sounds pretty dang similar...

You notice any loss of power? When mine started misfiring, it was very noticeable.

I had bad 2 3rd gens do that. One was a bad coil. The other was a dirty or failed injector.

Good place to check anyhow.



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Ok so you've got the basics done so that's good to hear, but bad for the diagnosis. Pull one of the easier to reach plugs out and take a look. It should have a mocha/brown colored ceramic insulator in the center and the electrode and ground strap should be dark but no black soot or oil residue. That'll give you more clues on how it's running. Your fuel data looks good so I don't suspect the injectors or O2 sensor but it's not a sure thing. Normally when the O2 sensor fouls it'll trend too rich or too lean and that'll show up in the fuel trim data.

So I pulled my passenger side spark plugs and tested the related injectors. All spark plugs looked just as new as when I installed them, and all injectors gave 14.5-15 ohms (healthy is between 13-18 ohms)... very strange
Unfortunately that's as far as I got with that debacle, had to replace my steering rack today and it was an 8 hour nightmare
No loss in power, but like I said I've also been dealing with it to some degree since I've owned the car so if there is a loss I probably wouldn't be any wiser. There are times when I'm heading to/from work and when climbing the same hills I always do, sometimes I will zoom right on up it and pull clear through the tach - other times it feels like I'm stuck in 4th gear while still riding in 2nd because it's so unreasonably sluggish to the point it feels like a 3VZ could walk me without even trying. I've never known why that is and could never find any definitive answer, but the car doesn't run rough or anything when it happens, just slower than hell. Perhaps that's related perhaps it isn't?
What I DID notice is the engine vibrating much more harshly. In park and neutral it idles smoothly as it should and looked perfectly still, but when in it was in gear it was visibly vibrating and the looser components like vacuum lines and whatnot begin to get that fuzzy/blurry look to them if you know what I mean

These v6 are not known to be power houses. Hence why they supercharged them.

Did you check for vacuum leaks? As that can give you a rougher idle as well. So can a dirty IAC valve.

I just know when I lost a cylinder due to coil and an injector, it was extremely noticeable.



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You sure it's not just the torque converter shudder that these all seem to have?

Mines the same way. Like you said, it's almost a lope while in gear, in neutral or park it's smooth.

Just a thought.

Your ST and LT fuel trims are great. Curious to know what the ST and LT fuel trims when the lope appears?
And when was the last time you looked at/cleaned the throttle body and IAC?

I agree with this. It seems his engine is idling at 600rpm in park and neutral. It should be idling at 750 in park/neutral and 600 in gear with foot on the brake.

If he’s idling in gear at 450rpms it won’t be happy.


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Ha, that's funny you mention the 3VZ. So your 4Runner really isn't happy at all if you feel like the 3.slow is faster than your 5VZ-FE.

I think it may be time to think outside of the box then like you are suggesting and look at less likely culprits. I would rule out any mechanical failures like a torque converter as if that was giving you grief (and yes, when they fail they slow down the vehicle as they become very inefficient at transferring power to the transmission) it would not be fine one drive and then broken the next. It would do it on every drive.

These are some thoughts but without driving your 4Runner I really do not have any clue how to help at this point:

• ECU - capacitor failure
• Throttle Position Sensor
• A rogue sensor that sometimes is out of range and other times is not

Do you ever see any "Pending Codes" on a code reader? Some are two trip codes that need to happen in a row in order to turn on the CEL.

This is how they should look.


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It's the torque converter knock. I'm tellin ya......

Clunks in drive at a stop, but park or neutral is doesn't right?

If you had a cam issue it probably wouldn't be associated with transmission engagement.

Thanks for all the replies everyone. I might have misspoken, apparently the chop is in reverse too

Yep I just took off and cleaned my TB while testing my injectors and checked for leaks afterwards, and found nothing. To boot I can also deduce one isn't present, as if there was such a bad leak to the degree it's causing the changes I've noticed I would certainly be throwing codes and be in limp mode by now - let alone have nearly flawless fuel trims. And while it could result in a loss of power, it would also increase idle as well; and my engine speeds are also much too low for a leak
About a week ago, and a few months before that. Then probably 2 or 3 times last year. Pretty much every time I've taken it off (not because of problems, just cause why not at that point). IAC was also replaced in 2021
Those figures were taken while the sound was occurring actually. Though I suppose I should probably check again after a week or so
I'm at 600 in gear, 750 in park
Yeah I'm starting to think it's something less severe than a miss, really starting to lean towards the cam gear alignment I've read about. No pending codes currently, the only codes I throw these days are for a dying wheel speed sensor and p0420 once in a very blue moon. TPS was replaced in 2022 so I highly doubt it's that, but I'll look into capacitor failure. It only feels that slow on hills for what it's worth, flat ground is a totally different story... but unfortunately I live in a very hill-y area It's not, I can hear it clear as day coming from the valvetrain. I didn't mean to imply it was associated with transmission engagement or that I was having any sort of transmission problems; just gave an anecdote of what I perceive to be inconsistent power at times on the chance it might be related, in case someone knew better. Personally I'd attribute it to my driving style and entering hills in different gears depending on the level of traffic before assuming it was due to internal damage/wear, but that's just my opinion. I could very well be wrong