Things to try:
-New spark plugs. Even low level misfires that don’t throw a CEL can cause surging. Replace the COP boots while you’re in there and use a bit of dielectric grease to make removal easier and reduce the chance of arcing.
-Dirty MAF (or MAP, depending which this engine has) sensor. Clean it.
-Slight leak in the post-turbo intake tubing. May need a smoke test to find this.
-Torn BOV diaphragm. This can have the same affect as a leak in the tubing.
-Leaking wastegate actuator tubing or solenoid. Wastegate is opening and closing when it shouldn’t. Pressure test the line from the solenoid to the wastegate at the turbo. It should hold pressure (don’t go higher than 15psi in that system, no compressors).
Also possible, but less likely is that The torque converter is locking and unlocking repeatedly making the rpms fluctuate. Not sure how to test for this without a dedicated Ford diagnostic system.
Last edited by tcp71; 01/19/20 11:06 AM.