Hey guys -

So I'm having trouble diagnosing my surging idle when the brakes are depressed at a stop. The idle is also way too high (1200) after the car is warmed up.

So far I've replaced the spark plug wires, distributor cap, set the base timing (but high idle prevents me from doing it properly), cleaned the throttle body, checked for vacuum leaks with a DIY smoke maker, and cleaned the little fitting that connects the coolant line to the IAC from the block. The problem persists.

Based on what I've read, it seems like it could just be that my IAC has decided 30 years was enough and it's just not working anymore. I was thinking I could try replacing it to see if that fixes it. There is a genuine Toyota option for like $180 and a Standard Motors brand one for $85. Has anyone replaced their IAC valve with either of these options? Can I safely go with the cheaper one? Anything else I should check? Thanks all.

1991 Toyota Pickup, 5 speed. 199k miles.

 

Rarely will any option be higher quality than OEM. That being said, before you spring for a new IACV, have you checked that the O-ring on the idle adjustment screws isn't compressed and hardened? A new O-ring will seal it up and prevent the adjustment from wandering. Have you tried turning the idle screw in to lower the idle?

 

The Standard Intermotor import part AC141 is the same thing as the OEM, and it's made in Japan too. It's just a re-boxed part just like Beck/Arnley use to re-box Toyota parts. It does come with the rubber gasket that seals it. Mine was doing like yours randomly, and yes it was the IACV causing it.

Bought mine from RockAuto. Don't know about the WVE part that is cheaper than the Standard part. The Wells part could possibly be the same re-boxed part.

 

The adjustment screw is all the way in and my idle is still at about 1200 rpm when the car is warmed up. The o-ring does look compressed and hardened, but when I used my smoke tester I could not see any smoke coming through it. Should I just replace it anyway before splurging on the IAC?

 

Awesome - thank you for this info!

 

Yes replace the o-ring. My old o-ring on my 92 just fell apart when I tried to take it off.

 

Let's face it, the o-ring is probably a factory installed item. Little bits of rubber like that don't last 30+ years very well. Probably a good idea to replace it, whether it's the actual problem or not.

Before you put the new o-ring in, put a thin layer on Vaseline, or electric dielectric grease, on it.
Makes it last a lot longer, and the o-ring will seal better.

Good luck!
Pat☺