Being relatively new to the 4Runner scene, I'm still working on gaining knowledge/experience on the little things.

Question: Is it normal for the engine idle to change when removing the oil filler cap on the valve cover? If so, why? If no, what could cause it?

My 2 cents worth: Found today that NAPA sells the 80A fusible link (that I blew on New Years Eve, 35 miles from town. Toyota dealer only had 1 in stock and I wanted a spare. Toyota cost: $10.58, NAPA cost: $2.79.

 

Oh yeah, that's proper.

Why? Because you've just created a vacuum leak in the PCV system, consequentially resulting a vacuum leak in the post-MAF airflow to the throttle body/intake. That causes a discombobulation betwixt the signals given to the ECU by said MAF/VAFM(the air flow metermajiggy)for the air/fuel calculations and corrections to be performed by which and the actual rate of the airflow provided with the oil fill cap off. That extra airflow being unmetered as such.

Simply put, vacuum leak bad. Make engine run poorly/too lean. Definetely would cause idle to lower, and become even more of a problem if one were to drive or run the engine at high rpms with a vacuum leak of that quantity left unchecked.

Sorry, I'm in an odd mood right now, not to worry. I see my former self on his way to meet me as we speak, should be here soon...

Yep, I likes NAPA too. For the most part, but I'm kinda hard to please, so they say.

 

lol, thanks for the indepth, probably technically correct reply.

 

You bet. Glad you made some sense of that, I'm still recovering from the new years all-nighter. Ouch! Too much of that raspberry vodka whatever the heck it was.