Fuel 5.0 Lost Fuel Mileage , Loads Up At Stoplight

[Steve 1993 GT]

Hi folks, I just discovered your web page and this is my first post. I have owned a 1993 GT automatic since 2000. It has 68k miles on it as of this posting. Lately I have taken note of my fuel mileage dropping by about 60 miles per tank and when it idles after warm up, it tends to load up and lope like it has a performance cam in it. sorry but that's the only way I can describe it. There are no codes or check engine lights at this time. So far I have changed the air idle control and cleaned the throttle body. I have also pulled the vacuum line from the FPR and I am not seeing any fuel. I have also cleaned the mass air flow sensor with the proper cleaner. I have pulled and inspected the spark plugs and they a dry. there does not seem to be any excessive smoke or black on the rear valance (it is white so it would be noticed) this car is all stocks with no mods at all. Sorry in advance for any improper etiquette while using this forum. Any help or clues are greatly appreciated! I failed to mention it has a 5.0 engine but what else is there?

 

[jrichker]

There is no mention of any mods or add-on aftermarket parts. Are we to (maybe rashly) assume that this is a completely stock engine?
If not, please list all your mods.

No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.

 

[Deleted member 215073]

He did state the engine is 100% stock.

 

[jrichker]

He did state the engine is 100% stock.

I missed that, so what else can you tell us?

 

[5.0Droptop]

What are the plugs gap setting? With only 68k has it ever had a tune up?

 

[Dan02gt]

When's the last time the O2 sensors were replaced? They are cheap and go bad over time.