: TERRIBLE Gas mileage "help"

04-27-09, 05:23 PM
2000 STS
112k miles.

No matter what I do, I can not avg above 19mpg with this car.

Most of my driving is highway other than about 6 miles of a 50 mile
round trip.

I drive this thing like there's a egg under the gas pedal and it wont go above
19 on a tank.

Ive been running Mid/Prem, checked plugs (good), tested for cracked plenum (good, no crack), have checked vacuum ( holds steady @ 15 ), checked for rolling resistance, ie brake issues, or bearings.

Please advise

:hmm: :banghead: :wtf:

04-27-09, 08:45 PM
Make sure the engine is reaching full operating temperature - a faulty thermostat will keep you in closed loop, with rich mixtures and use lots of gas. Also, are you getting torque converter lockup? Check for codes - especially P0741.

04-27-09, 09:20 PM
.........yeah, that, and also, when the engine is warm, remove the beauty cover and locate the FPR (Fuel Pressure Regulator) on the right rear fuel rail area. A small round top widget with a vacuum nipple connected to the throttlebody. Start the car and pull the vacuum connector off the FPR. Raw gas ?? Not good. www.rockauto.com and 10 minutes with the hairpin clip retainer.

Do you have a stethoscope ?? El cheapo at Walgreen. Replace the chest diaphragm with 18" of rubber vacuum line from AutoZone or such and use it to snoop around the intake area for vacuum leaks. SSSSssssssss.......

As long as the engine cover is off, is the PCV system intact ??? From the rear cam cover to the inner front of the intake manifold, 3/8" hose/pipe/connector. From the throttlebody to the front cam cover - same size pipe.

Change to a WIX air filter. (If you haven't replaced it within 12,000 miles......)

04-28-09, 05:47 PM
My money is on the FPR.

04-29-09, 10:12 AM
Obama warned you to pump up the tires and reduce rolling resistance.

04-29-09, 09:34 PM
Thanks SUB.....

I'll try the FPR 2morrow, I'll let you know..


05-06-09, 10:18 PM
No gas in FPR, no vac leaks, PVC system appears to be intact
:banghead: :wtf: :anibs: