Morydees

Quoting myself here because I have an update: I called my mechanic and it turns out the "mystery part" was just the entire throttlebody assembly (and all the attached sensors like TPS and such). I don't know why he didn't just say that originally but that implies they don't know what's causing it and they wanted to just replace everything. He was trying to get those parts used since all of them new are probably $$$. Unfortunately no one has them used locally so new is the only bet. I'm really torn here because I could end up spending double what I paid for the car just to take stabs at random parts and it might not even get fixed.

Thanks for the quick responses guys! I can't believe I never thought to check the O2 sensor and if my mechanic hasn't yet, he should have!

I found your thread in searching because I have a similar problem. Unfortunately, I cleaned everything mentioned and I still have the two main symptoms: 1) extremely bad gas mileage (9-10 mpg highway) and 2) running rough at low speeds and occasionally it'll fall on it's face with no power from a stoplight. And recently when it's warmed up, sometimes it'll be hard to start I took it to my mechanic and we did a full tuneup, replaced all filters, replaced the catalytic converter, checked fuel pressure, compression check and checked for codes. Nothing at all. The puzzling part is he mentioned something strange that he thought it might be. It's a fuel injected car obviously but he said there's some sort of "carb-like" part that he thinks is the problem. That and he can't seem to source the part new or find it at Pick-U-Part. Does anyone know what that part could possibly be called or have any other things to try? I greatly appreciate it! Mory 1988 Pathfinder SE V6 Los Angeles