Pearl_SH

I bought my 98 prelude a year ago and I remember it doing this from the beginning. I didn't think anything of it at first, the humming went away pretty quickly. But when its cold, below 20 degrees or so, the car will rev up and down, making a humming noise for 5 or 10 minutes while it is warming up. Is this normal? it makes the sound now that the weather is warmer, but only for a few seconds. Do I have an air leak? Is the oil being pumped up prety slowly? Has anyone experienced this? If you have any advice please let me know. Thanks.

pIERCE

Typically that is the IAC valve that's gone bad or needs to be cleaned. Get the gasket/screen(one part) for the Idle Air Control Valve and replace and clean, you should be good. It's on the front of the intake manifold.

itsthatprelude

maybe EGR valve also

BlaqkLabeL

Honda Prelude Forum

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minilogoguy18

FITV, on the bottom of the TB. Remove it and take the back plate off and turn the wax plunger all the way until it stops, replace plate and use red loctite on the screws, done.

For the posts above, EGR valve has nothing to do with the idle and if the IACV was bad it would bounce no matter what temp it was.

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New Formula Red 93 BB2: JDM OBD1 H22a/T2W4 Accord Euro R transmission

Phryxis

yeah I was going to suggest the Fast Idle Thermal Valve too. can't say I'd recommend red loctiting anything though

my FITV was sticking and the idle was bouncing, after I cleaned it out, the idle stopped bouncing.

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colin

KCMachine

spadeprelude

check ur map sensor