I have a 2001 4Runner and every time I start it up, the engine "pulsates". It's kind of a small vibration that pulsates. It is not violent or anything but I can certainly feel it inside the car. It goes away when in drive and after the engine warms up a little. I think it started when the weather got a bit cooler but am not positive because I did not own it for much of this last summer. Also, I replaced the spark plugs back to a dual tip because I read somewhere that single tip spark plugs can make 4Runners pulsate. Anyhow, if anyone has any suggestions, please let me know. Thanks!

 

Is it when you first start up the engine and it kinda revs high for a moment. I have that problem with mine.

 

I think the increased RPMs are normal for any car at startup. The pulsating lasts for several minutes at least...until the car is put into drive.