2000 Buick Century Ltd. 3.1 liter Fuel Tank Removal

I doubted that my answer was high octane gas when the mechanic told me that but who am I to dispute what a mechanic says? I go to this shop because it is within bicycling or even walking distance from my home. I don’t have the luxury of being able to easily have rides to & from a garage too far to walk to. I cleaned the outside of my idle air control valve. The plunger seemed to be tight so I compared it with a new one at a parts store but the new one was just as tight. Plus, no trouble code for that or anything else, so I figured that if I relaced the IAC valve, I would just be throwing even more money blindly at this problem. I don’t remember checking the IAC passage but there’s not much distance at all between the hole the IAC sits in and the air tunnel. Could the IAC valve be faulty though, even though it seems as good as a new one? Yet I would think there would be a trouble code, that’s the problem, no trouble codes at this point.

IAC valve failure won’t set a code.

That’s because it’s an engine control device.

Not an emission control device.

Tester

I had my engine anslyzed for $100 where no trouble code was seen but somehow he found thatcthere was random misfire in all but one cylinder. Wouldn’t he somehow also have found evidence of any IAC valve problem?