***SOLVED***
Idle adjustment screw needed new O-ring as mine was 33 years old and completely toasted. The dash pot seems to be working correctly, it was likely the new ECU I bought that wasn't meant for an 85. I put the original computer back on and it's purring now. THANKS!


Hello,

Finally got the 85' 4runner started. It's doing some weird stuff and I can't figure it out. When I first fire it up it's idling around 850 rpm. After driving around a little bit, when I come to a stop, it's idling around 1500 rpm and never goes down. If I turn the truck off for a couple minutes, fire it back up, then it idles at 850 rpm.... Is the "dashpot" to blame? Also there is the idle adjust screw near the front of the plenum, it's changing nothing with several turns in either direction... Reason for not working? Thanks

 

The dashpot valve can cause intermittent high idle, but I haven't heard of any aftermarket replacements, just through Toyota and it's unbelievably expensive for such a tiny piece of plastic. I've tried to pry mine apart without destroying it, but never got it open, just gouged it up a lot. A new one might not fix the problem, either. The throttle cable can stick, as can the butterfly valve. Adjust the dashpot plunger so it doesn't contact the throttle stop anymore and see if the high idle quits. Nothing bad will happen if you disable it. It's there to prevent the throttle plate from snapping shut, which can cause the last bit of fuel to not burn off, but in practice doesn't seem to affect much.

The adjustment screw not working makes me think that the o-ring is old. Replace it with the closest size you can find in the hardware store bin (50¢, tops).

 

Awesome information, thank! So just take the idle screw all the way out and there is an O ring down in there OR around the base of the screw I'm guessing? Interestingly enough... I had a problem getting this thing started after the rebuild and replaced MANY parts. One of them was the computer. I just put the original computer back in to see if it was good, since the truck is now running... and what do you know, idle problem gone... just ran around town a bit and came back and when I stop it quickly (1 second or so) goes back to 900 rpm. I think the computer I bought was off an 88 or 89, mine is an 85. The part number is identical as well as everything else one it. Did they change anything in these micro computers for the later 1st gen runners?... Even though it's the same part number? The truck also NOTICEABLY runs smoother and the exhaust is MUCH quieter with the original computer back on it. I don't understand HOW, but I'm clearly keeping the original on there and going to sell the other computer back on ebay (bought it for 75 bucks so I'll make a little money =])

 

Dude, you were right about the O ring as well. Drove to O'reilly with a flat head screw driver. Popped the hood and took the idle screw out. The O ring was FLAT all the way around and it's surface sat recessed in the screw so it was making contact with NOTHING lol. Went to pull it off with a hook tool and it just disintegrated into several pieces... it was done. Got a few new ones and now the screw actually ADJUSTS the idle. Thanks a million.