Does anyone have any experience diagnosing a problem with the fast idle thermo valve?

My Haynes auto manual says that when the car is cold, if you push down on the plunger (can't recall exact term), you should hear air woosh out. It then says you should warm up the car so the fans kick on. At that point you should not hear any air when you push down on it. The Haynes manual says if you get air coming from it when warm, it's bad and needs to be replaced.

Well, I tested that this past weekend and even when the car was fully warm, I could hear air wooshing from it (even before pushing down on the plunger). So if the Haynes manual is right, the part needs to be replaced.

Can anyone confirm whether this is correct? I ran out of time to clean the part this weekend, so I plan to do that shortly, but am just wondering if anyone has experience with one of those going bad and if they could confirm whether the Haynes manual is correct that I actually need to replace the valve due to the sound of rushing air when the car is warm?

Thanks,
Jonathan

 

Hey Jonathan,can i ask you why you checked the the FIT valve(Fast Idle Thermo valve)?
Only cause there are three valves on the intake that work together(IAC valve,FIT valve and the stating air valve) but you are correct about the FIT valve,i have the same manual as you do but did you read all of section 18 in chapter 4?

 

On Hondas, the basic check of the FITV would be to put your finger on the lower port of the throttle bore. When the engine is cold, you should feel suction. When the engine is warmed up, there should be no suction. (To check when warm, you can hold the engine at 3,000 rpm until the radiator fan turns on, then let it idle and then check.)

The attached pic. is from the the 5th generation (e.g.,94-97) service manual. But, it is the same basic check for most other Hondas.

Do you have starting or idling problems?

 

Also note, the FITV can be adjusted. I would think/try this before replacing IF there is a problem with it.

 

I had already cleaned the IAC this weekend but I did miss the part about the starting air valve. I'll have to go buy a hand-held vacuum pump as I don't have one of those on hand. Someone previously had recommended checking the FITV, so I was reading what the Haynes manual said about that - even though I knew that wouldn't solve my warm idle issue.

 

With the engine warmed up and the fan running, when I covered the intake port hole in the throttle body almost completely, I could feel suction and the engine idle did seem to change. So presuming the Haynes manual / your test is correct, it looks like I do have a bad FITV valve.

The real problem I'm having is the lack of a smooth idle where I get vibration in the steering wheel, feel vibrations in the seat while sitting at a red light, and sometimes get some hesitation during moderate acceleration. While looking at the IAC and cleaning the throttle body, I just happened to test this part since I saw the Haynes manual describe the test. I will mention that last winter I had the erratic idle issue a few times where the idle would surge then drop, surge then drop, etc continually. But that only happened a few times after 30 minute drives which I don't typically do anymore. From what I understand that can be caused by the FITV (correct me if I'm wrong).

 

Are you talking about the white ring on top? If so, I can confirm that it is completely snug - not loose. With that being the case, what else would there be to adjust?