Poor Mileage, Runs Great Though

[captaineric]

Have a Jasper rebuilt engine in my '92 Sport and the mileage is lousy, around 13 or so (was around 15 when the engine was new but has dropped over the past several thousand miles). Checked the fuel pressure regulator and pressure is fine at 34 psi with no sign of leakage into the vacuum line. However, pressure drops to 0 immediately after shutdown. But, engine always starts right up if I turn the key on until I hear the fuel pump stop running before cranking. No CEL's noticed. Want to change the O2 sensor but looks like a ***** to get to the plug connector on the back of the engine block. Any suggestions? Have ordered a new FPR since I have the original and figure it's time to change it regardless of the gauge readings. Any other ideas? Engine runs great! Good power, no hesitation, smooth idle.

 

[jimbo74]

its old...... my explorer got worse mileage than that.... you might wnat to give it a tuneup, new plugs wires, filters, tranny fluid, tcase fluid, rear diff fluid, make sure good gas is being used (watered down gas will kill mpg) and replace the o2 sensors, look into the cats as well if they need it...... pcv, egr, clean the maf

 

[captaineric]

Engine is nearly new, no cat..

The Jasper rebuild only has 3-4,000 miles on it and all components such as wires, plugs, etc. were replaced at the install time. I bought the Sport in the Middle East and brought it home with me so it is a catalyst-free model. I have Borla headers and exhaust, K&N filter, BBG throttle body and Granatelli MAS. Mileage used to be better in Middle East but then it was hotter there as well! Tranny runs just fine: shifts and appears to be OK.

 

[jimbo74]

im surprised as to how they let you have it here..... not all states have the CARB standards, but most wont allow a car without emissions equipment...... what about fluid changes?

 

[captaineric]

Fluid change

Auto trans fluid plus torque converter fluid/filter was changed at the time of the rebuild install. Transfer case and diffs are several years old. What bothers me is the sudden decrease in mileage. For years, it's been around 15-16 mpg. The sudden decrease of 2-3 mpg seems unusual considering nothing else was changed.