My 01 Navigator 5.4 with 183k miles has an issue with "almost" stalling. After heavy braking then immediately pressing the accelerator, the tach will sometimes drop to 200 or 300 then back up above 1k and runs fine. For example, traveling at 55 to 60 mph, start braking to make a 90 degree right turn. Let off the brakes and press the accelerator while turning and the near stall occurs. I can almost predict when it will happen. Already replaced the IAC and recently a new fuel pump that failed. Considering replacing the vacuum rubber connectors, elbows, etc. as my next step. I'm thinking vacuum leak. Suggestions or ideas? I'm sure this issue has been thoroughly discussed, didn't have time to find the post.

 

Welcome on a board !!

 

Does this happen every time you depress the brake pedal?