I have a 2005 Nissan Sentra which just had another engine put in (thanks to a bent rod) with 114k miles on it. When I'm driving around town, everything seems fine. When I get on the interstate and am going about 75mph, the engine hesitates and pressing on the gas does not help, but instead drops me down to 60mph. My mechanic stated that it was the fuel injectors so he replaced them, but it didn't help (on the interstate only). Then he added more transmission fluid, but it still didn't help. Any thoughts? There is a high pitch sound that's been there since I bought the car a couple of years ago. Additionally, it sometimes takes 2 or 4 times to get my car started. Any thoughts?
Have you checked the fuel filter?
Not yet, but I'll suggest it.