'87 4runner starts up fine, but when it warms up the idle, which usually stays at ~1000 RPM, it goes from 800-1000 RPM.


I have already checked/cleaned the EGR, and just replaced my throttle position sensor. I just looked at the Idle air control valve, but wasn't sure how to check and clean it. Also, I didn't really check for vacuum leaks, because I thought a vacuum leak would cause issues even when running cold. If it could be a vacuum leak, is there a specific location I could check?


Also, I should mention that I haven't owned this vehicle for long, and looking at the past owner's receipts, they seemed to have some temp issues, could that be causing it? I honestly don't know if my engine is overheating because my temp gauge is busted :/

 

I would definitely try to figure out what temperature you're running at, whether that means fixing the temp gauge or getting a handheld temp gun.

The idle surge (I think that's what you mean, it's surging back and forth from 800 to 1000rpm?) Is annoying for sure, but if you're overheating you could cause some other serious problems I think.



Edit: Also, did you adjust your TPS after installing the new one, then set your idle?

 

OK so sorry it took so long to reply, but after installing a new temp gauge, I can confidently say it is not a temp issue. The surging starts as low as about 130F.

And yes, I adjusted the throttle position sensor.