It seems to very slowly getting worse.

At idle it is rough, but not so much like a stumble, but more like a cycling vibration that is on a 2 second interval. A/C is not on so I know it isnt my compressor cycling..

You guys have any ideas as to what might be the cause?

 

Dirty Fuel Filter?
Fouled Plugs?

 

Fouled plugs, faulty coil pack, faulty wires. That would be my first guesses.

 

Ok, so here's what I'll try.

1) Plug Wires - Original 85k miles
2) Fuel Filter - probably original.
3) Check plugs - replaced about 20k miles ago.
4) Live with it unless it gets really bad. I dont want to replace coil packs unless I have to.

Thanks for the Suggestions!

 

Test everything before you go replacing it. That will save money and time.

A multi-meter will handle the coil packs/plug wires.

 

I have an 03 V6 and it does the exact same thing from brand new on. I've noticed it in some other 4runners too, so it's not an isolated quirk. If you figure it out, please post.

 

I have a 98 v6 with similar engine vibration symptoms - sort of an on and off cyclical vibration. Sometimes the idle slowly drops to 500 RPM, the vibration increases, then it quickly pops back up to ~650. Nothing extreme, just annoying. Replaced fuel filter, plugs and wires, cleaned TB, ran several cans of fuel injection cleaner. No change - still the same. I wonder if it is supposed to be like this?

 

No, it's not.

 

No, it's not supposed to run that way...

Have you seen this? Good reading material that might help...

https://www.yotatech.com/forums/showthread.php?t=35112

 

Thanks Bamachem! I'll have to try that first.

So maybe the cycling we feel is caused by slightly higher compression in some cylinders, or maybe clogged injectors in some cylinders?

Where can I buy some Seafoam? Does Autozone carry it?

 

I got mine from napa. look for a metal can, maybe 7 or so inches tall with red and white graphics.

 

Thanks again Bamachem!

I'll definitely try this stuff.

 

My rpms do not change during the vibration. How bout yours?