High Idle help

[crash813]

'89 V6 with auto that i've had for a few months and going thru it. Just got done with plugs, replacing a few vacuum hoses, re-routed one or two that were incorrect, replaced valve cover gaskets so the intake came off and put new upper manifold gasket on, thoroughly cleaned TB, new PCV valve, and full timing belt/waterpump.

Now, its idling too high. 1k at cold startup..... once warmed up 1k in gear, 1500 + in park. Strange thing the other day was that I ran it up to the store, so high idle on the trip there. Turned off car for maybe 5 mins, then got back in to go home. Motor was hot, and once it came on, normal idle, maybe 600 or so. Idled great all the way home, maybe started getting a little high towards the very end.

My initial thoughts were vacuum but I replaced all the cracked hoses and went over the connections like a 100 times. My next guess was possibly PO cranked up the idle screw to compensate for poor running previously or maybe timing off. Then the hot start where it idle fine doesn't seem to fit.

Looking for suggestions on what to start troubleshooting.

Also, anybody have any idea what the RPM dial behind the glove box does?

thanks

 

[crash813]

Solved the problem this weekend. Documenting on this thread hopefully that it helps someone in the future.

Turned out the coolant lines going into the TB were plugged up with metal bits and corrosion. Looked like half an input nipple somewhere corroded off and started the backup and all the pulling and flushing I just did pushed everything downstream into it finally closing it out. Flushed both hoses and the TB itself and wouldn't you know it.....nice idle once she warms up. Actually a little low, all the vacuum leaks and the partial clog, i'm guessing the PO had the idle screw as low as it would go. Time to check the timing and idle her correctly now.

Stay dirty my friends! :hungry:

 

[supra6m]

Huh.., interesting. I will be looking into this on mine. Thanks.

 

[ToyoTech]

yea the idle air control valve needs coolant to work

my IACV started to get weak and no new replacement possible. i took mine apart and adjusted the valve completely shut so it basically disabled the IACV. i basically lost cold start idle but i can still start it even when cold. i also disabled the cold start injector since its not needed any more. now i just her up and its already at warm idle, sure i still need to warm her up or drive it easy till at operating temp.