'99 4.0L OHV Engine Hum 5-speed manual

[ajfender]

When the engine is warm, occasionally i have a deep hum coming from under the hood. it only occurs when i am idle [with the clutch in or out] or below 1750 RPM in first gear. as I speed up it goes away. there is no mechanical loss or electrical loss with the hum...it is just annoying and deep sounding.

thought it was some defect with the air box so i upgraded the factory air box with a K&N, but have not changed the MAF sensor b/c it did not look damaged. and this noise is not all the time i am at a red light [or idle]...only if i stop and go or sit idle for a few minutes, tends to happen more in hot humid temperatures rather than cold temps, but only when the engine is warm.

i have not changed any clutch components and i think the time may be approaching for a new clutch system b/c not many clutches i know of last over 100k miles. the clutch still works great, no trouble shifting between gears, but i do have to rev it up a bit more to start on an incline (not incrediably more though), and i have noticed it get softer over the years (normal wear). my current clutch is not squeeling or making any noise...i just have this engine hum "tone"


any suggestions? i have no fluid loss, and about 127500 miles....great mechanical condition besides this annoying hum.....


thanks fellers....

[KPT]

IAC. Do a search, very common.

[ajfender]

that's the best lead i've heard of.

i got to a point that it's annoying when it happens I have stopped into a service shop and tell the guys if they can identify the problem and fix it i'll do it on the spot and get them a case of beer....but no one knew what it was or any idea what it was so no one won a case of beer.... thanks man...i'll look into it.

[AdvanceExpo]

99 Ohv?