Re-doing a new post with new info. Problem has been there for a few years. Idle surges between 1k and 500 after fillup anywhere past 3 quarters of a tank. Goes away after a few minutes of driving normally. Sometimes lingers for a few driving sessions if not enough gas is burned off. Rear purge and filter box changed with motorcraft part, and front solenoid changed with motorcraft part. No check engine lights ever thrown.
Just got forscan back on my laptop and can use that to check, but at current idle shows nothing relevant. Have not yet put gas in it again with forscan up. Any suggestions? About to replace boost solenoid due to full throttle or highway speed throttle surges as well, but seems unrelated.
Car's now at 69 thousand miles, all stock otherwise. Clean air filter. This car is no longer a daily driver, and I'm thinking about getting it in the air and dropping the tank to take a look inside. Not sure where else to look. Vacuum lines all seem good. Spark plugs are 8k miles old, give or take.
I changed the front solenoid after they came out with just the single part. Should I instead buy the whole octopus as they call it and change lines and all instead? It seems unnecessary as all my lines looked good, but I'm not sure anymore.