HELP! 2000 Taurus 3.0 OHV Vulcan Hesitates at stoplight

[Z3T3C]

Engine is surging/hesitating while in gear when vehicle is stopped, but throws no codes. No noticeable hesitation, surging, or bucking while in motion. What has been replaced: DFPE Sensor and DFPE hoses (one caused vacuum leak), fuel pump, fuel filter, IAC with Motorcraft IAC, camshaft synchronizer and sensor with Motocraft parts, and PCV rubber elbow (another vacuum leak). Pulled spark plugs all check out and still gapped at 0.044 inch from last tune-up. Some of these parts above replaced, for other codes which have all been cleared now, but the hesitation or surging hasn't gone away. The PCV rubber elbow and DFPE hoses were replaced, because of vacuum leak testing as they were the only 2 issues. BTW it does it whether the engine is cold or warmed up and even does it when the heat/ac is off. It's my grandmothers car, but I can't seem to find answers on how to fix the issue anywhere without parts that has already been replaced. I appreciate any help or suggestions.

[Z3T3C]

Also, since the throttle body was off when doing the cam synchro I cleaned the butterfly valve and throat with throttle body cleaner, a toothbrush and a rag. Replaced the throttle body gasket when putting it back on and sprayed down the MAF sensor with CRC MAF sensor cleaner.

[shorod]

How much build-up was on the throttle plate and in the upper intake? If it was pretty nasty, chances are quite good the valves are similarly dirty. I'd suggest you pick up a can of SeaFoam and use it as the "cylinder decarb" steps call out. I typically use 1/2 can rather than the 1/3 can that's called out. Also, you don't mention the condition of the spark plug wires. While not a fun task, you really should consider replacing the spark plug wires if they appear to be original. While you're doing that, it's not much more expense to replace the spark plugs.

-Rod

[Z3T3C]

There wasn't a ton of build up and it all came off fairly easy. Not sure if one of the previous garages cleaned it up when they changed the IAC (recently failed) along with a fuel system flush a couple of years ago. That's a good point about the wires. When I pulled the plugs they were NGK iridium plugs, so they were changed. I asked my grandma about it and she said someone from her church did it for her 4 years ago but wasn't sure about the wires. She has put about 15,000 miles on the car in the last 4 years according to her receipts, so I don't think the Iridium plugs need to be replaced as you can get up to 100,000 miles on them. On the other hand , the wires appear to be OEM with the factory labeling for each cylinder printed on them so they could be suspect. I will report back once I have an opportunity to change out the wires. Thanks, Rod.