Okay, my first post. I have a 2003 Ford Expy 4.6L. about a year ago it threw a plug and I took it to the stealership for the "Ford approved insert" they also did a tune up. Since then it ran fine for a while, but then recently (3months)started running rough while idling. kinda surges a little from under the hood but no visible change on the tac. I got a code reader and there are no codes. I removed the throttle body and cleaned it thoroughly(it was nasty), put a new IAC and EGR valve and a new PCV valve. I checked all the vacuum lines and even sprayed around the base of the throttle body to check for gasket leaks. I also cleaned the MAF. No joy. Anybody have any ideas. I am kinda lost now.

 

Did you replace all the spark plugs recently? Put new coils on it? I would check your ford bill and see what they really did because it sound like you need a tune up

 

Thanks, I'll try that