01 Miata. Completely stock. This issue came up out of the blue overnight.

Advance goes very low and into the negatives on throttle tip in. This is causing low speed driveability issues. It otherwise operates perfectly fine when not at idle / tip in from idle.

No CEL. Replaced MAF with no change, cleans both of them. Did tune up stuff, plugs wires, all good. Cleaned oil and junk off crank trigger (This is still suspect as well as the MAF). What is the issue here? Where else should I be looking? I don't know much about VVT, but could the actuator be getting stuck? More oil pressure on revs gets it moving again?

 

Ha! Stumped you.

Anyway, this popped up on the way home. How in the world could this be my problem. I guess I'll try and take it apart today. I don't recall EGR failure being very common.

 

 

PCV valve itself was stuck. Stuck open.

​​​​​​I took it off, filled it with Marvel's mystery oil and cycled it back and forth with a screwdriver until it was working properly again.

Problem solved.