1995 f150 4.9L 2wd Manual
It started back in Nov. I was normally getting 19-20 mpg surprisingly. It has always been good to me. Overnight I'm getting 12mpg. I've had it in the shop on the computer before and they couldn't make sense of it. So here is all I've changed.
Throttle Position Sensor
Hell I even hallowed out the catalytic converters cause i thought they might me plugged, and I still have had no luck.
Like I said it happened overnight, it wasn't gradual, so I doubt the valves are plugged. Yes, I have noticed a loss of power some as well. I don't know what to do, I'm out of ideas. Please help!
1 Pull the computer codes with a paper clip and find a new shop.
2 Connect a vacuum gauge and see what it reads.
3 Pull your spark plugs and examine them for signs of misfire and do a compression check while their out.
A Haynes manual has a pretty good section for trouble shooting the electrical and fuel systems and is well worth the $15-$20 it costs.
Do you have dual tanks? Try this, fill both tanks, drive for a couple days. Remove the gas cap from the un-used full tank. If fuel spills out, the fuel pump on the tank that the truck has been running on may be bad.
There's a check valve that goes bad & causes the other tank to overfill.
Also, the O2 sensors should be changed every 70,000 miles according to Bosch.
Would have trouble doing that with the tanks, rear one has a leak, so I only put about a 1/4 tank in it.
As for misfiring I haven't noticed that..
O2 sensor I doubt would eat 8mpg, I have thought about it, but doubting
Mass air aye? Yeah I may check that out, they are a little pricey new, maybe pick one up at junk yard. Thoughts?
The times I've taken it in to the shop for computer codes has been a joke, since its a 95 they said I'm screwed, that ya can't seem to get good codes out unless they are 96 or newer. Sick of giving them money to plug it on and get no where. First time couldn't get any, then they said airb/aird valves (which I also replaced) and it did nothing, had a code that said like throttle rod I believe, but didn't make any sense.
Try cleaning the Mass airflow before you replace it, Shop told my buddy he needed anew fuel pump in his ranger with the 3.0 v6, I got there after he had replaced the pump, started it up. still doing the same chuging now power thing, I pulled the MAF and cleaned it, reinstalled ran perfect.
At one time the auto manufacturers recommended replacing the O2 sensor at certain mileage intervals but now its only if they fail a test. Some believe the sensitivity of the sensor slows down with heat and age but a code should set if the sensor is too slow. Naturally the makers of O2 sensors will recommend replacement just like the quick lube places want to change your oil every 3000 miles. Some mechanics will replace them if the cats have been clogged or if there was a chance of contamination from an engine malfunction. I did replace two GM O2 sensors @ 130k that did test out OK but were oil soaked and it did help performance slightly.
My 95 has 224k and only the Map sensor has failed. If your 95 300 has two air tubes from the filter box to the TB then its SD and OBD1.
The tests and codes for OBD1 should be easy for any garage worth doing business with. They are easy to pull without special tools and they will lead you in the right direction for what is ailing your engine. The trouble codes indicate a fault in a particular circuit. It could be the sensor or its wiring that's setting code. Don't replace the component with out testing it first.
BTW my 95 just got 20.5 Mpg @ 65 mph on a 280 mile trip. It will usually get 16.3-17.5 on the weekly commute which I consider very good. My worst, non towing, tank was 14.7 during a week of snow. Hauling 4100 lbs will drop the mileage to 11-13.