Originally Posted by genso
I rechecked iac ohms and temp coolant they are good I have taken off and cleaned egr and iac and throttle body and checked for blockages and there were none...what does that tvv do? can it go bad? I took it for a test drive and it was actually worse after all the cleaning I did. One thing to mention, I tried checking iac with a 9 volt battery and connecting center to positive and lower one didn't hardly move the valve and the upper one partially closed it. I soaked it in seafoam creep and could turn it by hand... it isn't supposed to go all around is it? It only turns about 3/8 inch or so.
Do you still have the basic scenario problem: okay when warming up...not okay when warmed up ?
About the IAC valve:
that little "door" only moves enough to be able to completely
close and open the little opening. So when you turned it with your hand, were you able to completely turn the valve such that the opening was fully closed and opened by the door? Or did you feel resistance and were not able to fully close/open the door with your hand ?
As the factory service manual says:
At low temperatures the IAC valve opens and the air flows through the IAC valve and the throttle body, into the air intake chamber. During engine warming up, even if the throttle valve is completely closed, air flows to the air intake chamber, thereby increasing the idle speed (first idle operation).
When I cleaned my IAC valve, I also used a 9 Volt battery...but it barely moved the little "door" (maybe I got unlucky and had a drained 9V battery), but I hooked up two wires to the car battery. I used the car battery instead of the 9V battery. For my situation, the little IAC door did NOT close all the way. I verified that there was no blockage or debris inside the opening and around the door... So I loosened the two little screws holding the thermostatic spring housing and slightly turned the housing with the screws and re-tightened. Re-did the battery test and verified that the door fully opened and fully closed when the wires were hooked up the two different ways. Which way you have to turn it, it depends...I don't remember which way I turned the spring housing. You can see the screws on the left side of the IAC assembly (by the fingers in the photo below):
That was my scenario...on this forum most people don't mess with those two screws holding the spring housing...people just clean everything and they're good to go!
So I am just telling you this info to keep in mind...
Make sure that the rubber "frog" gasket between the IAC assembly and the throttle body is installed/seated properly and that the 3 hoses (2 coolant and 1 air) are connected in the proper location.
If you have the original ECT sensor, I would highly recommend to change it, even if it seems to be okay. An ECT that is going bad will cause all sorts of problems...so might as well be safe and replace it. It's not expensive and it's really easy to replace.
I am sure more experienced users will provide more info...
EDIT: Oh, and the TVV controls air/vacuum to the vapor canister for fuel vapor based upon if the engine is cold or hot. If this branch is not operating properly, idle/stalling issues might arise. On 1996 and newer, the 4 cyl. i don't think has the TVV anymore...instead it's a vacuum switch. I have a 1996 4 cyl with an electric vacuum switch (hence why you don't see it on my engine...in the photo I posted)