SLIGHT DROP IN FUEL MILEAGE AND ACCELERATION POWER
I have a 1997 Ford F-150 4WD,124,000 miles. I am one who monitors fuel mileage each time I fill up. Over the past 3 years I have been struggling with trying to pinpoint exactly what may be the cause of this ongoing delema. My truck used to get 14.5 to 15mpg consistently. I keep my truck tuned up regularly and change fluids and filters at regular intervals. At first, when all this began, I notced a slow drop in mileage that was somewhat erratic, ranging from 14mpg to 11.2mpg. Most of the time I average 13- 13.7mpg now. I have had the catilytic converters replaced 18,000 miles ago, O2 sensors replaced 45,000 miles ago. Also I have replaced the EGR valve, IAC valve, TPS,VCV, MAF and EGR control sensors over the peoriod of time in question.Recently I performed a vacuum test which the results show good under no load conditions(17-18hg at idle and 20-21 at 2500rpm), but under load or drivability shows a large drop in vacuum durring normal acceleration, down to(7- 4hg) then will recover and stabilize when crusing speed is reached,45mph to(10-12hg). When accelerator is mashed to the floor, there just isn't the get up and go it used to have. The truck has a steady idle and acceleration, no knocking or pinging, jerking or anything else out of the norm.No trouble codes show on the scanner. I still need to do a compresson test and coil pack test,but the spark plugs show normal wear. Can you help me with any suggestions?
What part of the country do you live in and what kind of fuel do you use??
June 6, 2006.
June 6, 2006.
I live in the Phoenix, Arizona area and have been using regular unleaded fuel.
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