So I have what I believe is refereed to as a "rough idle" on my 2003 Grand Marquis. While in my car at stop lights it kind of sounds as if one of the cars around me is bumping their base really loud. In fact for a while I thought that's what it was. I guess I would also say it sounds like if you were to lightly roll your tongue with your mouth closed. It doesn't feel like the car is about to stall or anything...it just sounds...weird. The 2 main things I think are worth noting are that when the car is in motion it seems to run fine. Acceleration is great and all that. However at stop signs and traffic light it sounds rough. Which brings me to the 2nd thing I think is worth noting. It only does it when it's in drive or reverse. If I put it in park or neutral it idles fine.
Within the last 500 miles I have changed the air filter, cleaned the mass air flow sensor, and changed the fuel filter. This was all kind of a "screw it, let's just do all this other crap while I'm at it" weekend. To be honest I can't nail down exactly when this weird sound started. One reason for that is the blower motor resistor had been broken on my car for several months. So when I was driving it the AC would pretty much always be on full blast. The constant extra noise made it hard to keep an ear out for trouble. This includes ruining a couple rotors. Since I replaced the blower resistor and replaced all the brakes and rotors it's really highlighted the crummy idle :/ Go figure right? Any ideas?
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Funny you should mention the EGR. Google a picture of the idle air control valve (IACV) and see if that is what you are referencing.
Also, I'm curious where the noise is coming from in general. I totally missed that you said it changes when in or out of gear.
If you put the car in "2" and accelerate, let off completely, accelerate, etc..., do you get clunking from the driveline when you get off the gas pedal quickly?
Another thing to consider is that the transmission may be making the noise. Try to get someone to hold the brake and parking brake while shifting from N to R or P while you listen outside the vehicle to locate the point of origin.
Haha, yeah, I guess that was a weird way to describe it. I just ment with your lips closed just enough for your breath to escape...it doesn't matter. There is no ticking sound while I accelerate. It's weird, if the car is in motion everything is totally fine. It's just when it's stopped that it does it, and like I said before, if I put it in park or neutral is idles fine (which makes it really hard to diagnose on my own). Something with the exhaust did cross my mind. The only thing that makes me thing it's something more to do with the engine is that it's fine in P and N. That's just a hunch though.
I have the throttle body, TB adapter, and idle air control off of the engine now and am cleaning them up a bit. It was a little gnarly in there, especially the part of the TB adapter feeding the EGR valve. Hopefully it helps.
After you've been up to highway speeds for a while in the 03 to 07 models the knock sensor starts working when you come back to an idol and it sits right on the firewall and controls the fuel vapor line coming from the charcoal canister for reburn it's normal to hear those going tap tap tap tap tap it's not your motor it's okay but what I would get down to is changing your fuel pump control module in the trunk it's behind the spare tire see if that helps I'd say the next thing to do is have your fuel pressure tested if you know your wires or cops and plugs are good you don't lose any coolant and you're not overheating or anything
Haha, yeah, I guess that was a weird way to describe it. I just ment with your lips closed just enough for your breath to escape...it doesn't matter. There is no ticking sound while I accelerate. It's weird, if the car is in motion everything is totally fine. It's just when it's stopped that it does it, and like I said before, if I put it in park or neutral is idles fine (which makes it really hard to diagnose on my own). Something with the exhaust did cross my mind. The only thing that makes me thing it's something more to do with the engine is that it's fine in P and N. That's just a hunch though. I have the throttle body, TB adapter, and idle air control off of the engine now and am cleaning them up a bit. It was a little gnarly in there, especially the part of the TB adapter feeding the EGR valve. Hopefully it helps.
After you've been up to highway speeds for a while in the 03 to 07 models the knock sensor starts working when you come back to an idol and it sits right on the firewall and controls the fuel vapor line coming from the charcoal canister for reburn it's normal to hear those going tap tap tap tap tap it's not your motor it's okay but what I would get down to is changing your fuel pump control module in the trunk it's behind the spare tire see if that helps I'd say the next thing to do is have your fuel pressure tested if you know your wires or cops and plugs are good you don't lose any coolant and you're not overheating or anything