2000 F150 5.4l 87,000 miles. I believe i have a vacuum leak but am not really sure and need to locate it. I have a consistent beeping sound when my truck is in R,D,1 or 2. It is only audible with my foot off of the throttle. This includes 55mph if i just let off and let it coast. It is also audible for a second when the truck is put in park and then shut off. It has been a month or so and have yet to throw a code. I had a loping idle about 2 weeks ago but have not noticed that since then. Is it a vacuum leak, if it is where??
Also i believe i have bad valve stem seals due to blue smoke on startup. (not sure if that has anything to do with it.) I'm 17 and would like to learn something and also have a chilton manual.