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Discussion Starter #1
I changed my injectors out with some used lower mile injectors. I now have code P1316 and rough idle/choppy under load.

I tested injector resistance through the 42 pin engine harness abover the driver's side valve cover. All of the injectors tested at 3-3.5 ohms through that harness so in my mind that eliminates the valve cover harnesses as the problem or I wouldn't get a resistance reading. My truck is an '03 so it has the updated style valve cover harnesses that can't be "fixed" with a quarter.

If an IDM is going bad, what are the usual symptoms? are they the kind of thing that either works or don't work?

Where is the IDM located?

Thanks
 

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The IDM is actually in the drivers side ft fender, kinda right behind where the F350 chrome emblem is. Because of their location, it is not uncommon for water to enter the IDM and cause problems. BUT you need to do a "buzz test" and allow the IDM to further resolve codes. That's really what the 1316 is telling you. It sees an electrical injection problem and want the IDM to test each line to find faults.

What kind of scanner are you using? Is it capable of queering the IDM (most aren't...)?

Also the '03s have a redesigned clip that makes the quarter unnecessary, but the connection can still fail.
 

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Discussion Starter #3
it was a bit of an ordeal but I got it figured out

I had a buzz test done

with a code P1275

I figured it was an injector solenoid problem so I switched the solenoid with one of my old ones and the problem was still there. I then realized that the armature in one of my "new" injectors was loose so I switched out the new injector with one of my old ones with the newer solenoid on it and it runs perfectly now.

it looks like the armature is held on with a screw with an odd head shape which I guess makes it "non-field serviceable"? I tightened up the armature screw by spinning the armature clockwise but I couldn't seem to get it as tight as my old injectors so I put one of my old ones in.

And for future reference, the IDM must monitor current flow through the injector solenoids so it can sense if the hydro-mechanical part of the injector isn't working. The IDM is much smarter than I first assumed.

If was to do this all over again, I would have just bought a brand new set of solenoids and installed those instead of replacing the injectors. the only problem I was really having was cold start issues due to the solenoids being weak with high mileage.
 

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Discussion Starter #4
after a bit of research I think i'm going to put some locktite on the armature screw and put that injector in the truck to match the rest of the low mileage injectors.

I just need to find a 4.5 mm security/Nintendo bit to tighten that screw up properly.
 

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ebay has those little screw bits fror cheap!
 
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