MattAudette

Can anyone tell me what this noise is? I'm getting this on my 2003 F-150 4.6L. It's loudest from the K&N intake before I take it off. I'm not sure how to describe it other than a popping or a quick sporadic duh-duhduhduh, so here's a video:


-No check engine light what so ever. It isn't burned out though since it shows with all the lights when I start the truck.
-The noise started coming home from the mountains while the engine was hot
-Now it happens almost immediately from a cold start
-After warming up a little, the idle isn't steady. It'll rev up and make the noise, then die down and rev up and make the noise again.
-It continues if I take the filter off
-It continues if I take the K&N black intake tube off of the manifold too. Though I have to keep it close so the mass airflow sensor still feels something. Sounds like it's probably inside the manifold, but I can't tell for sure.
-It goes away if I rev the engine, but not immediately. In the split second it continues when the engine revs up, it doesn't increase in pitch or frequency.

I've never heard a noise out of any car like this. My biggest car friends are thrown for a loop too. Any ideas?

MattAudette

We replaced the idle controller valve.

We tracked down the noise as coming from the idle controller valve by pinching to tube going from that to the intake. We took that apart, cleaned it, and put it back in. The awful noise went away, but it wasn't idling steady. So we dropped a new one in there and voila! Now she's running like new. I can feel more power too

This probably should've been in the maintenance forum, but hopefully it helps someone out. Thanks for the suggestions in the maintenance forum guys.