Suddenly poor MPG
Thread Starter
|
New User
Joined: Apr 2002
Posts: 1
Likes: 0
Suddenly poor MPG
1993; F-150; 4.9L 6-cyl.; E40D auto. trans.; 2-wheel drive; 112,000 miles
I noticed poor gas mileage on a 120-mile trip. The gauge dropped from full to below half, a sudden change from previous performance; it used to drop to the 3/4 mark. Over several weeks I calculated the highway MPG as 16.1 and the city MPG as 13.7. I took the truck to several mechanics and told them of "poor" gas mileage, a rattling sound when accelerating, and what seemed to be less power than in the past. The 1st mechanic said, "Got no codes". The 2nd mechanic changed the oxygen sensor, and later the EGA valve. There was no improvement. A 3rd mechanic ran a compression test (160-165), changed all the plugs and fuel filter, said the engine was running lean (based on fouling of the plugs), and recommended a valve job. The 4th mechanic put an injector cleaner directly into the injectors (?). (I've put 4 bottles into the tank.) A 5th mechanic checked the timing (4 degrees off) and suggested I use a different brand of gas, which I did. I've spent $720, over 4 months, and still get the same MPG and poor power. Any suggestions as what to try next? Does anyone with a similar vehicle get better mileage? Highway 18-19 MPG, town 16-17?
Thanks,
j_raven33
I noticed poor gas mileage on a 120-mile trip. The gauge dropped from full to below half, a sudden change from previous performance; it used to drop to the 3/4 mark. Over several weeks I calculated the highway MPG as 16.1 and the city MPG as 13.7. I took the truck to several mechanics and told them of "poor" gas mileage, a rattling sound when accelerating, and what seemed to be less power than in the past. The 1st mechanic said, "Got no codes". The 2nd mechanic changed the oxygen sensor, and later the EGA valve. There was no improvement. A 3rd mechanic ran a compression test (160-165), changed all the plugs and fuel filter, said the engine was running lean (based on fouling of the plugs), and recommended a valve job. The 4th mechanic put an injector cleaner directly into the injectors (?). (I've put 4 bottles into the tank.) A 5th mechanic checked the timing (4 degrees off) and suggested I use a different brand of gas, which I did. I've spent $720, over 4 months, and still get the same MPG and poor power. Any suggestions as what to try next? Does anyone with a similar vehicle get better mileage? Highway 18-19 MPG, town 16-17?
Thanks,
j_raven33
Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Suddenly poor MPG
Take it to a muffler shop and have your Cats tested, they should do it for free. One might be plugged up and in need of being replaced. Also, you might want to get a fuel pressure gauge and check that too.
Primary rig is:
95' F-150 EB 300/6 5 spd with 4" Superlift, MSD, Ram Air, Gibson Exhaust, 32" BFG Muds
THERE ARE SOME PICS IN MY GALLERY!! :-)
Then theres:
88' F-250 Superduty 351 + c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 and a
3 spd column shifter. Top speed, 65mph, Go Baby Go!
The newest addition to the Ford family is a 99' Mustang GT 4.6L
Primary rig is:
95' F-150 EB 300/6 5 spd with 4" Superlift, MSD, Ram Air, Gibson Exhaust, 32" BFG Muds
THERE ARE SOME PICS IN MY GALLERY!! :-)
Then theres:
88' F-250 Superduty 351 + c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 and a
3 spd column shifter. Top speed, 65mph, Go Baby Go!
The newest addition to the Ford family is a 99' Mustang GT 4.6L
Posting Guru
Joined: Jun 1999
Posts: 1,083
Likes: 1
Suddenly poor MPG
Definitely check your fuel pressure regulator. When it goes, though, you will literally be able to watch your truck/engine chug-a-lug gas through the gas guage...the drop will be astounding. That's how it was with my truck. Testing the regulator cost me about $20, and the total bill for test/replacement was less than $100. Mine is also a 4.9L, but a 90 model with more miles.
If you're getting 16/13 mpg now, after the drop so to speak, that's not too bad. Mine at best gets 16-17 in town and 18-20 down the road if I feed it the best grade of gas. I need to replace the fuel filter, though, that may help a bit.
Save yourself some $$$ and learn how to pull engine codes yourself. Go to this site:
http://www.dalidesign.com/hbook/eectest.html
It tells you how to do it with just a jumper wire. That's always the place to start (pulling codes). If your truck doesn't set any trouble codes, you might try a good tune up...plugs, wires, dist. cap. If your current stuff is stock, it's time for a change.
Do get the cat checked, it should be free at most shops. A plugged cat will rob your engine of power and you will definitely notice the loss. Post back and let us know what you find.
If you're getting 16/13 mpg now, after the drop so to speak, that's not too bad. Mine at best gets 16-17 in town and 18-20 down the road if I feed it the best grade of gas. I need to replace the fuel filter, though, that may help a bit.
Save yourself some $$$ and learn how to pull engine codes yourself. Go to this site:
http://www.dalidesign.com/hbook/eectest.html
It tells you how to do it with just a jumper wire. That's always the place to start (pulling codes). If your truck doesn't set any trouble codes, you might try a good tune up...plugs, wires, dist. cap. If your current stuff is stock, it's time for a change.
Do get the cat checked, it should be free at most shops. A plugged cat will rob your engine of power and you will definitely notice the loss. Post back and let us know what you find.
