Kenj

Hey forum,
I realize this is my first post but I've been browsing and successfully finding good info for a while now, and I honestly have to say the info here is priceless! I own a 90 Integra and I have the dreaded constant revving issue caused by an old/bad FITV (see: - not my video)

Anyway, my question is specifically about the FITV on Honda vehicles, what does screwing in the white plastic internals actually do, and more importantly why is it threaded to begin with? I'm assuming it was for servicing but I'm not sure even after looking into it for a while now, mine was originally about half-way threaded in, I'd love more info about the valve specifically.

I know that it has a heat activated "plunger" but does screwing in the internals actually bypass the system? I also read on a much older H-T post that It's not recommended to be closed all the way on cars with automatic transmissions (something to do with starting the torque converter). So I screwed mine in most of the way, and then backed it off a full turn and noticed the idle is much more stable but it still fluctuates a bit (up and down about 100 rpms at idle once at normal operating temp.

Thanks for any info you can provide and again I know the valve is the culprit I just want to understand It's internals and why It's threaded.

Warm regards, KenJ

94 Civic Si

Good question, I wouldn't mind learning as well!

testify

Did you check the vacuum line on the FPR?

holmesnmanny

It's threaded to allow for variation in the amount of air you're letting in depending on your climate on a cold start. Some climates that are supercold you can have it slightly out in relation to a warm climate to allow for a higher rev so the engine warms up faster in the morning when it's cold. Over time it does back out and you need to basically screw it down til it bottoms out then come back about a quarter turn or so. However, over time the internal seals will allow too much air in even when at the proper height. This could be what's happening. However, it could be the two orings that are in between the fitv and the throttle body or the intake manifold, whichever it attaches to, are leaking, or it could be the top one under the cap. I would replace the orings first since that's cheap. If that doesn't stop it then just get another from the junkyard or you can get another from Honda. If you buy a new one, mark it at both of the notches inside so if it moves you know where the factory spot is to screw it back to.

TomCat39

This is a pretty good explanation of why it's threaded etc.

I just wanted to add, it's also calibrated for the motor/tranny. Each intake manifold draws a different amount of air due to design differences. As well an automatic and a manual transmission ECU is programmed to run differently. I think the auto may need a touch more power to idle at the same rpm due to the heavier torque converter drag.

Anyways, the FITV is calibrated for each intake manifold and the transmission it's used on. This is why the non vtec D15B7 manual vs the D15B7 auto vs vtec D16Z6 manual vs D16Z6 auto all have different FITV part numbers. All 4 different FITV's are calibrated slightly different.

Also in addition to the seals holmesnmanny mentioned, the internal operation of the wax plug plunger can begin sticking and as the car starts to warm up, the bouncing rev begins happening. My car shows this on really cold mornings until the thing thaws out a bit. Mine needs to be replaced soon.

Correction. My surging idle had nothing to do with sticking wax plunger. I fouund I have been leaking coolant and I ended up with an air pocket that caused the FITV to not warm up and other issues. Car started to overheat last night as the final sign and I discovered the problem hose this morning.

So now I'm not sure if the wax plunger can stick if you clean the front side periodically.