I have a 94 runner with the 3.0 V6 and have been getting a 25 code (lean fuel mixture) I thought it was from a vacuum leak. I fixed a couple but the code keeps popping up. I have a cold air intake with a K&N filter that was installed 5 years ago. I only started getting the codes in the last few months. could the O2 sensor cause this? or maybe fuel pump? Anyone else had this code?

 

Unfortunately, it could be many things. Check again for vacuum leaks, that's the easiest. Use a can of carb cleaner on the hose endings and do a very thorough visual inspection. Make sure you don't use the cleaner on a hot engine!


Next you'll want to check the O2 sensor per the fsm with a multimeter. Or, if you know that you haven't changed the O2 and it's been 90k miles, it's time to change it anyway.


If that's not it... well... my code 25 was an exhaust valve that was stuck open. I had to do a complete valve adjustment and when you factor waiting times for the shims to come in, took me 3 days. Not a guaranteed fix either.

 

Thanks for the advice. I checked again and couldn't find any leaks. I am pretty sure I am due for an o2 sensor. Will try that and see what happens.