Hey All, I’m looking at a 1999 4Runner with ~240k miles that has an engine noise. I haven’t seen it person, but I had the owner send me a video of the noise.

Trying to determine if it’s the flex plate, or one of the front drive accessories, or something else. I’ve researched it and watched YouTube videos but haven’t heard something that sounds like this. Once I go in person, crawling under it should easily tell if it’s the flex plate. But if it’s not the flex plate, what else could it be based on the noise? The vehicle is in park I believe in the video.

I’m wanting to buy it for an weekend offroad rig and I’d love to get a 3rd Gen back in the fleet.

Trying to determine if the noise is internal to the engine, a cracked flex plate, or some of the other components that can cause a rod knock like noise. I’m competent on DIY repairs, but I’m not at the skill level to tear down a engine and do a rebuild.

Any insight is appreciated
4Runner Engine Noise - YouTube

Could be the flex plate. The noise is loudest at the back of the motor by the fire wall. Have the seller check the sparkplug also to eliminate a blown out plug.

Thanks for the reply! If it’s the flex plate, it will get quieter when in gear right? That’s seems to be what I’ve read.

I’m thinking about just going to look at it this weekend so I can hear it in person and get underneath to hear if it’s the flex plate. I’ll see if he’ll do the spark plug check or if he’ll let me do it when I check it out

I'm pretty adventurous when it comes to fix it uppers, this one would be too much risk for me with that kind of noise. That could be a lot of things, including main bearings IMO.

if the price is right? If your willing to replace the flex plate I'm going to assume your cool with doing an engine replacement. decent salvage engines are still pretty easy to find. I would think depending on where you live? plan on about 1K - 1.5K$ and you should be able to put a good quality salvage engine in with new timing set, seals.

when starting a project like that I would just plan worst case, maybe it's not as bad as it sounds but seems like most of the time it's worse.

It doesn't sound like a flexplate to me. They're typically more metallic/chattery type noise that will sometimes change with gear selection. Bring a mechanic's stethoscope with you. They're like $10 on amazon.

EDIT: A cracked flexplate also isn't usually rhythmic. They're more random and don't follow a pattern. That noise sounds rhythmic like a misfire/arcing spark plug boot/knock/rod bearing.

Also don't think it's a flexplate. It's possible it's valve knock and just needs a valve adjustment, that would be best case scenario. It sounds a bit like a 4Runner I bought for parts with a cracked piston. I was still able to drive it home but it sounded awful, especially once it was all warmed up.

Thanks for the insight everyone. I bought a stethoscope and I’ll see if I can poke around it this weekend to pin point the noise

Should've had the owner rev it up a little with the throttle. It's sounding pretty rough TBH - please don't pay much for it.

My first thought was a valve job before the video but it sounds more serious. I'm sure other members here with more experience can figure the noise.

I would try to limit the noise happening to the top-end or bottom-end of the engine.

I have heard noises similar to this with broken/cracked valve springs, but never from the 3.4L. If that isn't the case, and P/O beat it to the point of needing this much of a valve adjustment, I would expect it to have a warped head/bent cam.

I am not familiar with exactly how the cam preload works in these, but the machine shop I use has told me that not setting the 3.4 cam preload when putting the engine back together will cause a noise exactly like this, so it could potentially be that or the spring that it's preloaded with malfunctioning.

If the noise is bottom-end, I wouldn't even bother buying it unless you're good with doing an engine swap.

To bring this to a close, I asked the owner for the vin so I could run it. Long story short, it was a salvage prior total loss. Given the engine noise and the title, I decided to pass on this.

Thanks for everyone’s input, I appreciate it

Smart move. It sounded like a money pit unless you had a lead on a replacement engine.