When im in park or neutral my idle will jump iradicly from around 700rpm to 1500 rpm and sometimes up to 2k rpm. And its quick, its like it revs to 1500 and then quickly drops back down to 700 and then shoots right back up again. As soon as i shift into drive or reverse the idle stays steady at around 1k RPM. If im driving around and start to coast (im not on the gas and the engine isn't pulling the truck) the idle jumps up and down again. No idea what it could be. Any helpful thoughts??

1988 4runner
3vze
automatic transmission

 

im having the same problem...any help please

 

I know that I had this problem on my Honda. Ended up being a vacuum leak. Check all your vacuum lines. Ive also heard that if you have any air in your cooling system this could mess with your idle

 

Yes check to make sure you dont have vacuum leaks... get a piece of vac tubing and put to your ear and with the other end, put it around the intake and vac lines. Not sure about that one

 

I appreciated it. thank you.

 

yes, it was a vacuum leak mixed with a bad TPS.