Help ‘03 Gt Code P1409 Odd Symptoms

Evening gents! New here, not to mustangs though. This is my first 4.6 car, been good up until the last couple of months, been seeing code p1409 egr system circuit malfunction pop up, and go out a few times on it’s own. Symptoms include; after the engine is warm, and at highway speed, if I am at a very partial throttle, the engine bucks or jerks a little, like a hesitation or miss... Half or more throttle and it seems fine. Once I’m getting off the interstate and i need to let off the throttle to coast, the exhaust note can be heard ‘pulsing’ rather than a solid engine braking sound, and you can also feel that through the driveline slightly. Once I press in clutch and put her in neutral, the rpm’s will act eradic, dropping to as low as 400 and surging to 1000, hunting like that back and forth, the exhaust is also making the same ‘pulsing’ sound. Once stopped, typically the idle has stabilized, but as this get’s worse it seems to effect driveability anytime after this initial symptom shows up; especially at rpm’s below 2k. SUPER FRUSTRATING. As a first measure, I replaced egr regulator, to no avail. Then, removed and throughly cleaned egr valve and did what I could to test it with some vacuum, the diaphram appears to be fine. I’ve done that 3 times now, each time the symptoms and the code went away. I’m not really willing to fork over $180 for a motorcraft egr valve, so I ask... have you any ideas? I’ll admit, I haven’t tested a whole lot else, there are a few mods to the car such as:
Offroad H, catback, cold air, bbk TB etc. I have only really mesed with the idle stop screw a quarter turn or so just to keep the blade from sticking slightly and giving the feeling of a sticking gas pedal. Went with MIL eliminators when I did exhaust work, no other ideas as to what I could have done to stir up this mess. Any info or opinions greatly appreciated!

Okay, i’ll do some looking at that then. Thanks.

One more detail I’ve found to be rather odd, this issue seems to be sort of random now, with all this cold weather I’m not sure if that would effect it. The CEL has been off now for a few days and went off on it’s own. But symptoms still show up regardless. Anyway, I’m out of town and work a lot when I get back so please, any and all input is appreciated so I have some food for thought when I log back in. Thanks in advance.

Ok a couple months later and still no solution other than temporarily by cleaning the egr and lubricating it. I now have an houe long commute one way so today it got real bad in stop and go traffic! I made it to a spot where could pop the hood, and as soon as i disconnected vac from egr, the exhaust note returned to normal. I have looked over the wiring, pins and connectors within this system, dont see anything alarming. Orielly's said fuse 8...that fuse is good. So, am i looking at a new egr valve?

wmburns said:

In my experience the DPFE sensors fails almost as oven as the EGR valve does. However Ford has updated the DPFE sensor to reduce false DTC codes. Recommend using a Ford part or a well known name brand.

Click to expand...

Ok... So go with dpfe sensor first, see what that does. Is borg warner reputable when it comes to these things?

Ok, replaced dpfe sensor last night, took her for a drive and seemed fine, no cel light. But this morning on the way in, symptoms have come back as bad as ever and still no cel light. I had to pull over and disconnect egr vacuum it was so annoying! It appears my issue may be the egr valve itself at this point? I don't know where else to look.