My mechanic did a smoke test before and couldn't locate it a while back (year or so ago). Maybe I should get him to do one again. I changed my fuel injectors a while back thinking that was the issue, but no. Coil packs changed initially too. I get about 13 -15 mph these days. I hear the high pitched whistle but we cannot locate the leak. I think the next step is to change out the vacuum hoses. Snergy2007, if you find the leak, let me know where! I've tried many of the suggested options and no luck. My mechanic has replaced about everything!

 

I'm guessing you mean mpg not mph! That's terrible mpg if so. What are fuel trims (hot engine, parked) at idle & 2500rpm?

 

I've run into this before on the Lincoln LS V8 and it is actually pretty easy to diagnose.


With the car running, watch the fuel trim with a good scan tool like Snap On. You will see which bank is being trimmed back due to leaking injector. That makes the next step easier.


Once you determine which bank is leaking, remove the injector rail with the injectors still connected and put a blue shop towel under the injectors as they sit out in the open.


Within a few minutes, you'll see which injector is leaking. It will be very obvious.


Replace that injector and you're done.


If you want, go ahead and do the other side but typically I have seen only one that leaks at any given time.