I put a K&N intake in my 99 4-Runner. Since then, the shifting has been off. For instance, going uphill on the freeway, I take OverDrive offand the RPM's increase then drop about 300RPM's, I put Over Drive back on, and the RPM's increase! I talked with someone else who has a 99 Runner with a K&N intake and he is experiecing the same problems. Also, my mass air flow sensor went out a week ago. Just wondering if anyone knows of any solutions or have heard of this before! Any help is extremely Appreciated!!!!

 

The MAF problem is likely due to your K&N filter. Several people have had this issue:
https://www.yotatech.com/forums/show...6N+MAF+problem

I don't know if this affect you RPM (300 sounds very low)

 

I understand correctly what is going on with your shifting than I have the same thing and it always has been like that. Here is what’s’ happening with my 4runer (4x4, auto, 3.4).
Let say I am going uphill towing a bout and I am going 65 mph, if I push accelerator a little bit harder my rpm will go from 2000 (torque converter locked, 65 mph, overdrive is “on”) to approximately 2900 rpm (because torque converter unlocks), but if I will turn off overdrive at that moment my rpm will drop to around 2700 rpm.
And I think it is perfectly normal and not related to K&N. BTW I do not have K&N.
My $.02

 

It doesn't drop to 300 RPM's it decrease 300 rpms or so. For instance, going uphill turn OverDrive off, it will increase to say 3000 rpms then almost immediately drop to 2700. Then when I turn overdrive back on, it will go back UP to 3000.

I don't think it is an oiling problem though because the filter is brand new and never been cleaned or re-oiled!

 

No other thoughts???? Anyone?