Strange idle behavior

[Freb_mc]

Ok, so I hate making a post like this and cluttering things up, but it beginning to make me crazy. 1997 4runner limited 3.4 222k miles. It started a couple months ago, if the weather was warmer it would randomly idle to almost 1800rpm, turn the key off and restart, it would be fine. Cold start was normal only acted up after warmed up. I let it go as money was tight and it didn't effect driving it. I had checked vacuum leaks, all lines were good, nothing unusual (maybe IAC valve)? But now that the weather is warmer its getting worse and it doesn't help to switch it off and back on. I check the throttle blade and it has no notable play. I have been researching and haven't found anything quite like my issue. It doesn't feel like a miss anywhere, I'm kinda puzzled on this.

And this was all the info I had to go by until Saturday. My check engine light came on. PO125. So I looked this up on mitchell and on here which left me more confused. Everything from low coolant to temp sensor to O2 sensor? Coolant is good, temp reads good on the dash, so I am starting with an oem temp sensor and go from there. I have heard of the temp sensor throwing the computer into closed loop cold run mode and that causing fast idle or surging with hondas, but I am looking for a little light on the subject if anyone has an idea. Ordered my OEM sensor today and will have tomorrow. (I love working next to a toyota dealer) so we shall see what happens then I guess.

 

[shahsmerdis]

Ok, so I hate making a post like this and cluttering things up, but it beginning to make me crazy. 1997 4runner limited 3.4 222k miles. It started a couple months ago, if the weather was warmer it would randomly idle to almost 1800rpm, turn the key off and restart, it would be fine. Cold start was normal only acted up after warmed up. I let it go as money was tight and it didn't effect driving it. I had checked vacuum leaks, all lines were good, nothing unusual (maybe IAC valve)? But now that the weather is warmer its getting worse and it doesn't help to switch it off and back on. I check the throttle blade and it has no notable play. I have been researching and haven't found anything quite like my issue. It doesn't feel like a miss anywhere, I'm kinda puzzled on this.

And this was all the info I had to go by until Saturday. My check engine light came on. PO125. So I looked this up on mitchell and on here which left me more confused. Everything from low coolant to temp sensor to O2 sensor? Coolant is good, temp reads good on the dash, so I am starting with an oem temp sensor and go from there. I have heard of the temp sensor throwing the computer into closed loop cold run mode and that causing fast idle or surging with hondas, but I am looking for a little light on the subject if anyone has an idea. Ordered my OEM sensor today and will have tomorrow. (I love working next to a toyota dealer) so we shall see what happens then I guess.

You should be able to pull the temp on a scan gauge to see how wonkey the results are.. but sounds like a coolant sensor.

 

[Freb_mc]

I unfortunately don't have a scan gauge, yet, but I have access to a modus and autel scanners at work. It didn't act up on the way to work, cool enough in the morning not to effect it I suppose. I'll plug it in after lunch and see if it goes nuts again.