So I bought a 1995 4Runner swapped with a 3.4 from an 02 and it ran smooth with no problems for about 3 weeks. Recently it started to have a very inconsistent idle when stopped at lights. It ranges from idling low at 500 to way high at around 2500. When I tap the throttle and take it about 500 where it is idling it will usually settle back down to 800. It is not an issue with the throttle cable sticking. I am also unable to retrieve codes because the check engine light is disconnected. Thanks, any advice is appreciated.

 

You're just shooting in the dark without knowing if your truck is throwing any codes. Not too familiar with the 3.4 swap but hooking up the check engine light should be pretty straightforward. Also your engine has OBD2 a scanner should give you a fair bit of information.

 

Try checking for a vacuum leak . Easy to do and don't cost anything . While motor is running . Use carb cleaner or squirt bottle of water . Spray around all hose connections and intake manifold . If rpm's change you found the leak .