2000 Tacoma idle drops when cold outside

I have a 2000 Tacoma with the 2.4 L 2RZ engine. When starting, it idled ok for a few seconds, then, if it is cold outside, the idle will drop to a few hundred RPM, bounce around and often the truck stalled. Revving the engine for 60 seconds to warm it up works and the truck then drives normally after that. If it is a warm day, the truck will just start normally. I'm just writing the solution up so others don't have to through the same trauma.

Chasing another problem, (which turned out to be a bad spark coil), I replaced the IAC from the original to a new one from AutoZone. Mistake! The truck started doing the cold start problem above, but I had already thrown away the original IAC. But the new one couldn't be bad out of the box, right? So, I cleaned and then changed the MAF. No dice. Checked all the vacuum lines. Nope. Put in a new coolant temp sensor, spark plugs and checked the spark coils. Nope, nope, nope. So, I pulled the IAC and tested the resistance; it was way out of spec. So, stupidly, I went back to AutoZone and got another. The truck's cold idle issue was now even worse. I replaced all the vacuum lines with new ones. No luck. After some more work, I pulled the IAC and tested it - sure enough, it was also out of spec and a different value than the previous one, by a lot. I then went back to AutoZone and had the guy pull down yet another new one. I tested that at the desk in front of him and showed him this one was also way out of spec. He shrugged and put it back on the shelf for the next customer. So, I went to Kragen. They had one, but it looked like the same brand, and was scratched, indicating that it was also a return. I finally, spent the money and bought a new OEM one on Ebay from a Toyota parts supply place. It cost a hundred bucks more, but right out of the box it had the right resistance, and the truck idles normally at startup now.

The IAC part number for this truck is 22270-75051.

 

Welcome to the Forum!!

Toyota`s are known for not playing well with After market sensors.

Then after market sensors quality is very hit or miss as well.