2004 4.6L explorer Eddie 135000 miles.....runs rough between 1000 and 2000 rpms ....when in park pedal it up to 1500 rpm and it will go up to it but then will bring it's self down about 200 rpm and shutter......while driving it will run okay at higher rpms but if let off the pedal it will shutter slightly coming down rpms from 2000. Has new egr, fuel rail pressure sensor, Mobil 1 oil 0w 30 oil change, cleaned maf, cleaned intake out and checked for air leaks, new Motorcraft plugs, checked coil packs with tester, and new air filter. Stock motor no fancy stuff. Any takers on what might be my problem. All takers welcome. Thanks

 

You mentioned you cleaned your MAF, but can you get a reading on what the intake air temp is? It can only calculate air flow correctly if it knows the real outside temperature. My 08 had a clean MAF sensor but it was always 5 degrees off on temp. It ran the same way, and sometimes I could pull my foot off the pedal fast and it would die. I replaced the MAF and it's been great since then.

If its not that I would suspect its something in the idle circuit. AIC dirty maybe? Does it do it when the engine is cold, warm, or both?

 

Hey thanks you the reply .....it shutters a little when cold but shows the problem more when warmed up. And it doesn't have a iac it just has an egr valve.

 

There should be an IAC on the side of the throttle body. Triton (or cam phased engines) don't have the egr, but the rest did for emissions. Look on your throttle body, and and one side will be a larger throttle plate controller. On the opposite side there should be an IAC unit. When you step on the pedal slightly and bring the rpms up to 900-1000 the throttle plate is opening and the IAC should be closing down or it will lean out and run like poo. It decides when to open and close that based on input from the engine temperature, the outside air temperature, and how much fuel the engine needs. If all the readings are right but its just gummed up, it will close too late or open too late. Somewhere between 900 and 1500 rpm's it should be off idle and on the throttle plate control until you let off the pedal. Then its back to iac control.

My guess is when switching from idle air control to throttle plate, something is a little off. Could be the idle air controller (iac) or the maf reading wrong.

Now back to the EGR. sometimes and EGR can stick or hang and that can also affect the idle, but thats usually a constant idle problem, not an idle problem at a specific rpm range.

 

I have a new egr and I just had the maf temp check3d by my buddy it read 71 degrees and the temp out side was 77 to 78 degrees plus I was sitting in idle for a while after driving so the air going in should have been warmer then that do to a hot engine. I'm going to change my maf out on Frieday and see what it does. I may also have a miss reading o2 sensor. The thing about this vehicle is that it sat for almost a year or more on a car lot with no activity. In Ohio weather.

 

So to update my progress I in fact do have a iac but its located on top of my egr. so I just bought the new unit like a month ago so it work checked it. also bought a new maf and it made the engine run even better. but still a little rough idle around 1000 to 1200 rpm roughly. I believe this may be do to dirty or clogged injectors. I recently changed my fuel filter and it was bad. reversed the flow and almost like black muddy water came out. I believe ill pull them and have somebody sonic clean them and test to see how good they are working. ps shooter I'm sorry about running you around about a iac I really didn't know it was on top of my egr but I guess it happens. thanks

 

Before removing your injectors maybe try Chevron's Techron Concentrate in slightly higher than recommended doses to see if that doesn't begin to clear this up?

Its one of the better products that so many ignore thinking its another costly gimmick. I've been using it in several E250's with 5.4 motors and not a single issue with the fuel systems, one well over 275K miles.