Does this happen to anyone else?

[hulkmn069]

I am not too terribly concerned about this but i am wondering if it's happening to anyone else. I have an 04 4.0L laredo with minor mods. When i've been driving long enough to get everything up to temp sometimes my idle at a light will drop to 500 rpm. with the exhaust i have on it sounds cool but it's still odd. oh and it went away when i filled up with a tank of 100% dyno fuel then started again with the ol 10% ethanol crap. I am just wondering what anyone may think this is and if it's happening to them. oh and i know it's not the trans cause you can put it into neutral and it still idles low.

[Bob D.]

Have you checked for fault codes? The IAC motor can cause idle problems.

[hulkmn069]

no codes at all. i do want to get it on a better scanner and check the voltage readings but for the most part the thing runs fine and it just does this on and off when it wants to.