Mystery idle issue

So, I have a 2000 Tacoma, 2.4 l. When warm, and after running a medium RPMs, the check engine light sometimes comes only at stop lights and stop signs - when idling. P0446 - Evaporative Emission Control System Vent Control Circuit Malfunction.

Thus far I have replaced with new parts: 1) The gas cap. 2) The purge solenoid valve (twice) 3) All the hoses into the Charcoal cannister. 4) The Charcoal (aka vapor) cannister with OEM replacement. 5) The vapor cannister purge valve (twice). I tweaked the idle up from its usual 800 rpm to 950 to see if that made a difference, nope. I've even greased the gas cap to make sure the seal was good.

This started within a week or so after replacing the MAF and throttle position sensor, so maybe I knocked something, but they are not that close. The only thing I can't easily inspect is the seal at the gas line out of the tank and the fuel tank pressure sensor. The truck otherwise runs perfectly, it just might not pass smog inspection if the light comes on.

Anyone have better ideas before I drop the tank?

 

Some TPS sensors are adjustable, I'm not sure on your engine. From my experience it's the TPS. I've also has bad MAF sensors straight out of the box. So I'd look at those two. Best of luck

 

They all have a common wire… so I would suspect one of the parts.