ToyYodaCA

97 4Runner Limited, stock

I've been feeling a pulsing/intermittent vibration in the floorboard of my 4Runner for about six months. I did countless Google searches and checked damn near every thread tagged "vibration" plus other synonyms on YotaTech and other sites...no results.

In a last ditch attempt, I'm hoping that some of you experts could please help me diagnose this issue. Also, I promise to update my post with whatever the fix may be! No one likes an unresolved thread.

Here are the symptoms:

1) Gentle vibration from start/idle to 50 MPH (could be that road noise/bumpiness drown out vibrations above 50 MPH).
2) Vibration doesn't go away with a warmed up engine or after driving on the highway, nor is it more pronounced when the engine is cold or cool.
3) It is felt primarily on the driverside floorboard, but noticeable throughout interior.
4) The vibration pulses up and down with a constant pattern and intensity, regardless of speed or engine RPM.
5) The best way to describe the vibration pattern is like a sine curve - gentle up, crest, gentle down, etc.
6) The vibration is felt for as long as it isn't felt - about 2 seconds of vibration followed by 2 seconds of no vibration. This has not changed since I first felt it.
7) No major repairs performed in almost a year (no jostling of components). Last work done was thoroughly lubing drivetrain after chipmunk squeaks wouldn't go away (some zerks were stubborn and needed a higher pressure grease gun).
8) Regular maintenance done religiously.
9) Tires are just over a year old, balanced, and no bent wheel rims.

Any advice or input would be awesome, thanks!

ksti

It's possible your flex plate is cracked.

waskillywabbit

iTrader: (-1)

Or tires unbalanced, bad u joints, lots of possibilities.

:wabbit2:

lim50

any difference when brakes are applied ?

ToyYodaCA

No difference with the brakes applied. It seems totally independent of any input from the driver.

ToyYodaCA

I'm confident that it's not the tires, as the vibration occurs when the car is stopped.

lim50

automatic or manual trans,4cyl or 6 cyl ,How many miles ?

ToyYodaCA

Ha, sorry! That's kind of important info...

Automatic, 6 cyl, 200,000 miles

lim50

thanks, can you hear it outside of the vehicle? maybe loose heat shield on exhaust or cat converter.any difference between park and neutral at idle ? Does turning the wheels make any change?How about load on alternator,Lights,heater fan speed or a/c ? I am just digging here for clues This has got to be bugging the heck out of you !

ToyYodaCA

It is bugging the heck out of me. I think it is because I'd rather fix something before it breaks, because I know with my luck that it would die in the middle of the night, in the middle of nowhere, on a weekend, far from home.

No, there is no obvious sound outside of the vehicle. A loose part of the exhaust system is on the top of my list so far.

No difference between park or neutral at idle.

No difference when turning the wheels.

No difference with load on the alternator.

Thanks for responding!

lim50

Man I feel your pain. I am leaning toward a sympathetic resonance of a loose plastic body part or exhaust compo net. I drive a 87 4runner so i am used to some noise (LOL).I assume this noise appeared in the last six months or so.

lim50

Well one more thought .The only other moving part that I can think of that is NOT rpm dependent is the fuel pump. Maybe?

tunnelmotor99

I had a similar vibration on my 97, it was mainly at highway speeds. I replaced both u-joints and had the driveshaft balanced and the vibration was gone. The u-joint holes in the slip yoke were also egged out but they were able to hammer it back into shape. That was about 2.5 years ago and still works fine.

85GT-79FJ40

I would have the rear driveshaft checked out first. A bad U-joint or out of balance driveshaft will do this. But at that mileage and what you describe for a vibration it sure seems a lot like what I experienced on our old 2000 4Runner. It wasn't until gear oil started running out of the driver's side rear axle that I realized one of the rear wheel bearings was shot. It didn't change under braking like I would have expected had it been a wheel bearing. However with the rear jacked up off the ground I could noticeably move the wheel up and down on that side more than the other side. It was a pretty big PITA to fix too. had to make a tool to press the bearings out of an old axle housing and I had to buy the ABS ring and spacers from Toyota.

ToyYodaCA

Would a bad wheel bearing also produce a vibration when stopped? The symptoms that I have noticed match problems that are apparent when stopped or in motion, but not both.

What devices on the vehicle function at a constant RPM regardless of the engine RPM or speed of the vehicle?

ToyYodaCA

The fuel pump fits the bill of not being RPM dependent, but wouldn't it affect the engine if it was having issues? I haven't noticed any problems with stuttering or stalling.

Are there other non-engine/driveline RPM related components that could produce a rhythmic vibration?

ksti

Did you resolve the vibration issue yet?

85GT-79FJ40

I missed the part about it doing it when not moving. Usually anything engine related will change depending on rpm too. But i've never experienced a broken flexplate. I suppose if it were cracked it might only vibrate when it's out of square. A friend of mine had to change one a few year's back. Said there was no warning just all of a sudden his GF was stuck on the side of the road after hearing a horrible racket. Flexplate was cheap but installing it was quite a bit of work even with a lift and tranny jack in his shop.

thefatkid

Is your rear heater fan on? It under the passenger seat so kinda not matching your issue.

Does it happen with the key on and engine off?

The fuel pump could be making noise but still working. The tank is bolted to the frame so if you heard it inside, you should be able to hear it outside.

ToyYodaCA

The flexplate issue that I've read about on the forums doesn't quite sound like it produces the symptoms I've noted. Needless to say, I am scared that this could be the worst outcome, especially since it tends to fail catastrophically.

The rear heater fan is not on. The vibration feels like it is more power than what a small fan could produce. It also feels stronger at the pedals than it does through the seat.

With the key to ON and the engine OFF, there is no vibration. It only occurs when the engine is running. I haven't been able to hear the vibration from outside the vehicle, but I'll listen to the tank up-close next time.


Silly question time - do the alternator and other belts on the engine spin at rates that are somewhat independent of engine RPM? I noticed that there is a slightly higher vibration in/out rate when the engine gets above 3,000 RPM. This train of thought is headed towards cranky engine accessory pulley station. Just an idea...

Thank you all for your constant stream of suggestions and advice. I truly appreciate your time.