Funny Intake Noise, please help me diagnose!

[scurfman]

Hello, I have a 98 Ranger 4x4 with a 4.0 OHV. Recently it started making this really loud droning/siren noise. It will only do it at or near an idol and only when the engine is hot and the outside temp is hot. Seems to be worse when the a/c is on. The noise is definately coming from the air filter or intake. It has a Roush cold air intake. I changed the filter out with a new K&N but that didn't do anything. I also cleaned my MAFS but nothing. Does anyone know what this could be or has anyone had a similar problem? Thanks for your help.

 

[warhawk]

Sounds like your having the same problem I used to have. I replaced my Idler Air Control valve it's located right on the intake plenum just after the throttle body. Solved the problem for me. It's a common problem in the 4.0L OHV. The IAC get clogged with carbon and makes a noise similar to the one you described. Some people just try to clean them but that doesn't always work.

 

[scurfman]

Thanks!

Thank you for your quick response and the picture. I will try replacing this today. Thanks again. -Steve-