My 3.0 3rd gen.4Runner idling goes up and down. when cold from 500 to 900rpm when hot 880 to900rpm. you feel it very hard when cold.

TPS? There is no leaks in air filter. Timing is newly set.

 

Check the coolant. When my radiator was leaking and I didnt realize it my idle would fluctuate and I couldnt figure out why. Its a confused signal from the coolant temp sensor that went right away when I filled it up. Other than that, I would start with vacuum leaks.

Andy

 

Tps !!!

 

mine just did that b ut it was cause i left a vac line off and the computer readjusted for it after replugging in the line i had to "reset the comp" whcih means batt cables off for a cuple mins back to normal!

 

X2 for the vacuum leak

 

There are no leaks in coolant or vacuum. it might be TPS.. i'll check it tomorrow.

 

TPS is ok. I have no idea what's going on

 

At what frequency does it go up in down (i.e. How many seconds between it going up and down and back up again?) Is your A/C on? That causes the engine to idle up when the compressor kicks on, the idle down when the compressor kicks off. The A/C compressor cycles with a frequency of approx 45 seconds to a minute on mine... depending on the outside temperature. The A/C comes on when any defrost setting is selected on my 2002 without the A/C light being lit... I can't remember if my 2nd gen does that or not, but I think so.

 

try unplugging your tps..

my idle used to surge REALLY bad when cold and every once and a while when warm. then i unplugged it and it just idles high untill its warmed up now.

 

I don't use A/C at all. So it's something else. I'll try that trick with tps

 

Now i'm sure that it is not TPS. No changes when disconected
i have no ideas

 

im going through the same thing you are

 

How did you check for vacuum leaks? If you didn't already try, spraying carb cleaner all around the lntake and throttle body gaskets. Also try spraying around vacuum line connections. I know it's already been mentioned but vacuum leak is a pretty common problem for idle surging. I've also heard of O2's and EGR valve causing a simillar problem but only 1 case of each.

 

Like I mentioned above... A/C comes on automatically when you are on the defrost settings of your ventilation system. What frequency is the cycling?

 

My 93 4runner 5spd man 3.0 just started surging exactly as jamnik describes. The frequency is 1 to 2 times per second for me. All I have done so far is pull/push on hoses and injector connectors. Checked maf sensor connections. If I pull the MAF connector and start it, it will run for 1 second then die.