P0193 code/horrible mileage, no other symptoms. Help??

[townaj]

I have an 03 cobra that suddenly started getting horrid mileage partway through a tank of gas. It usually gets a solid 18mpg, and has suddenly dropped to getting less than 10 mpg. About a week after that happened it finally threw a P0193 code. I have tested the frp sensor and it ohmed out fine, and no fuel comes out of the vacuum port. It hasn't been running different, still starts up the same, and feels like it has the same amount of power so I'm not sure what is going on.

The car is all stock with ONLY long tubes and an O/R X-pipe. It was dyno tuned after the long tube install, so it can't be a tune issue. The car is my DD, so I need to get this figured out. I don't have the money to just start throwing parts at the car though. Any help or advice?

Edit: Also installed new O2 sensors with the longtubes under 2K miles ago. And the datalog through my SCT showed it adding more fuel than it had in the past, on this same tune.

 

[Bdubbs]

There doesn't necessarily have to be gas coming out of the vacuum line on the frps in order for it to be bad. I believe either the electronics or the diagram disc can go bad. Have you changed fuel filter recently?

 

[townaj]

Haven't messed with the fuel filter yet. Also forgot to add that I did some quick data logging through my SCT and it showed the short term fuel trims adding an unnecessary amount of fuel. They had never added that much on this tune before. Oh and O2 sensors are both new from Ford as of the long tube install about 2k miles ago, if that

 

[big dad]

What is the long term fuel trims reading? Plus or minus? If it's plus you have a vacuum leak. Check to make sure you have a strong vacuum signal at the FRPS at idle.

 

[townaj]

Long term ranged up to 1.20 at one point, never less than 1.0. Had a real strong vacuum signal at the frps when I took the vac line off, don't have anything to measure the exact number with

 

[townaj]

So the code isn't there anymore, but its still getting crappy mileage. I have an frps on the way, but I still don't think that's what this is. I traced the vac lines and all appeared to be fine, plus it idles fine still so there shouldn't be a massive leak anywhere. Any ideas?