Another low idle thread - To those who have fixed it

E

_ExpeditionMan

New member
I know I know this has been discussed dozens of times... I apologize and will try to make this one a bit different!

For reference: 1994 4Runner 3.0 5spd

This question is directed at anyone who has adjusted their idle (via the screw) and had the vehicle auto-adjust itself back to a low RPM.

Essentially, the 4Runner started idling at ~500 RPM a few weeks back. Did a cursory search on the internet, found the adjustment screw, adjusted, and thought I was good. I have attempted this a few times thinking maybe I was crazy, but each time I adjust to the FSM suggested 800-850 RPM the engine will drop back down to 500 RPM after a few days.

~1.5 weeks ago I had the Timing belt, water pump, and associated items replaced so I assume the engine has been timed properly. Additionally, if I give it some gas to hold the idle at ~800 RPM the engine runs super smooth and it only gives me slight vibrations at 500 RPM.

I am aware it could be a variety of things from vacuum leaks, to the TPS, or MAF... exc. What I am asking is:

1) Have any of you encountered this "self adjusting" low idle after idle screw adjustment?

2) Where would you start with the diagnosis of this?

I almost didn't want to ask this question based on how often this seems to come up for these. Thanks for the help and patience everyone.
 
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I had a idle screw that would "walk" from vibration. Ended up setting it and putting a dab of sealant on the top edge to keep it in place.
 
penbergm said:
I had a idle screw that would "walk" from vibration. Ended up setting it and putting a dab of sealant on the top edge to keep it in place.
Click to expand...

That's very interesting and something I had not considered. I may adjust it again tonight and put a mark to see if the screw is walking on me. I'd love for it to be something this simple!
 
I have the same problem. I think I have it narrowed down to temperature sensor wars. When the air temp is warm, the vehicle will idle too low until it warms up. When the air temperature is low, the vehicle idles too fast. I adjusted the idle speed downward last winter but had to raise it in the spring once things warmed up. I'm guessing it's the air temp sensor in the intake somewhere. I would welcome someone posting a picture of it's location. I have the 3.0 with an automatic trans. Maybe unhooking it will help the diagnostics.
 
Ahlem, it is normal in cold weather for the truck to idle at 2000rpm when cold started (in winter). Over the course of 5 minutea it will work its way down to normal idle. Thats completely normal. You probably know that - i just wanted to double check.
 
One good thing to do is a simple check of your throttle body. That thing gets pretty gunked up with carbon and can lower your idle if air cannot pass that flap. I just did a good cleaning of my whole intake system on my 3.0 and it evened out my idle.
 
Mine only worked it's way down to about 1200 rpm after it warmed up.
To the OP, did you fix your problem?
 
Ahlem said:
Mine only worked it's way down to about 1200 rpm after it warmed up.
To the OP, did you fix your problem?
Click to expand...

I used a small amount of sealant to keep the idle screw from walking and so far it has seemed to do the trick. I was going to update this once I had a few more opportunities to drive the truck.
 
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