Gas milage WOES!! 14.2 MPG!!!

[KevinT]

Hey all, having a slight money sucking problem here, I have a 300 I6, and bought the 6 for gas milage purposes over the V8, as of right now I'm looking to drop in either a 5.0 or a 5.8 in place, because they get the same milage I am right now! 14.2 MPG, shift at 2000 RPM, 5-speed + 2.73 gears 4x2 and EFI, have fiberglass bed liner to reduce wind drag, run on 87 octane arco or USA or costco brand gas, only fill rear tank, get 220 miles on a rear tank, then fill with 15.4 gallons of gas (reading last gas receipt) have 114,478 miles on the odometer, bought the truck used in Feb, gas milage has gotten consistantly worse since I got it, started out ~16mpg, I live in CA, if I rip off the emission crap will that help? or do I need a rebuild or what? The engine seems to be running rich, but I'm not sure how to check for sure on a EFI motor (last truck was a `87 S10 with TBI, waaaay different!)

HELP!!!



1995 F150XL - Reg cab/bed 4.9I6 5-speed Metallic Navy Blue/Gray int.
Mods: Topdeck bed lid, protecta bed liner, 1200 watt amp, 2 10" Rockford Punch Subs behind bench seat, sony cd-player, K&N Filter, Flowmaster 40 series + turndown in front of real wheels (no visible exhaust exit BFG A/T 31"x10.5"R15 and Rancho RS 5000 shocks

[jopey]

sounds like aclassic oxygen sensor problem.

that sensor shouldn't be more than $80 to replace your self

[PAUL_2]

Your mileage isnt the best , but its not really that bad for the engine , trans & gearing you have . First off , start with the basics , tune up items , plugs , air filter etc , check for any stored trouble codes . What makes you think its running rich ? Any black smoke etc ? Also check the fuel pressure , it should be 40 to 60 Psi . Proper tire pressure , alignment also help .

[KevinT]

Tune up was done by last owner in Feb.
air filter is fine (brand new K&N august) tires brand new (3 weeks old, 35 PSI)
I'm going to check the plugs tomarrow, taking truck into an engine shop wednesday to get the easy things checked (mainly so I can hook it up to an engine computer to check for codes, like you suggested) and also to test exhaust temp to see if running rich, and take a look at the O2 sensors. PLEASE SUGGEST ANYTHING I MAY HAVE OVERLOOKED!
oh...70mph on freeway = 1800 RPM in 5th gear

[warthog299]

Hello. Your mileage dosen't sound bad. I have a 1985 with the 300. I get, if im lucky 10 mpg. And thats with a new carb, egr valve, oxygen sensor and a full tuneup. I don't know what to do next?!

[insect2]

Check for exhaust restrictions. With that many miles the converter or muffler may be plugged up. Many tune up places can verify this or hold your hand over the tail pipe and see how much pressure you get at idle. It should blow your hand off at idle.

Also, I have the same truck. To determine your MPG you need to average it over many tank fulls of gass. Just one time can give a false reading. On my truck it can vary from 14 to 20, but then I take the average of all of them to get a true MPG.

[KevinT]

I've been keeping track of the milage since I bought it last Feburary...here's a link to where its been averaged out to 15 something, but the 2 most recent times I entered the info has been 14 something
http://w3.atlcon.net/~elongman/f150mpg/mpgreport.asp?vehid=412

1995 F150XL - Reg cab/bed, 4.9L, 5-speed, Metallic Navy Blue/Gray int.
Mods: Topdeck bed lid, protecta bed liner, 1200 watt amp, 2 10" Rockford Punch Subs, sony cd-player, K&N Filtercharger, Flowmaster 40 series + custom exhaust (no visible exhaust exit) BFG A/T 31"x10.5"R15 & Rancho RS5000 shocks

[KevinT]

I just started the truck, let it warm up and idle down to 700 rpm, doesn't blow my hand off at all, so i did the same to dads truck and it blew it right off...

1995 F150XL - Reg cab/bed, 4.9L, 5-speed, Metallic Navy Blue/Gray int.
Mods: Topdeck bed lid, protecta bed liner, 1200 watt amp, 2 10" Rockford Punch Subs, sony cd-player, K&N Filtercharger, Flowmaster 40 series + custom exhaust (no visible exhaust exit) BFG A/T 31"x10.5"R15 & Rancho RS5000 shocks

[insect2]

Well that means you have a restriction in the exhaust system or converter is plugged up. Replace or fix this problem and you should be ok.

[rpspwp]

I'm almost embarrased to admit I found my #2 & #4 plug wires swapped on my distributer the other day while cleaning the cap. I had always got decent mileage (14-15 or so) but it never seemed to have much power and sort of hesitated every once in a while. Who thinks to check the wires on the cap anyway? I always did a one for one swap when messing with them so I never had a reason to suspect that. Anyway, it drives like a new truck now! Surprise, surprise. I get 18.5-19 mpg (mostly highway) and power to spare. Anyway, couldn't hurt to check. FYI - The firing order should be 1-5-3-6-2-4.

[KevinT]

you have no idea how much I wish that was my problem, just ran outside and checked...1-5-3-6-2-4 with another wire labeled 3 to the coil, checked the plugs and replaced them this weekend, showed signs of being in there too long, no other probs (light brown)...I'm trying to find a place to either loan me a plasma cutter or to cut off the cats for me...if I'm taken em off, I anent putting new ones on until I have to smog it, save $$$ that way, plus it should be even louder then

1995 F150XL - Reg cab/bed, 4.9L, 5-speed, Metallic Navy Blue/Gray int.
Mods: Topdeck bed lid, protecta bed liner, 1200 watt amp, 2 10" Rockford Punch Subs, sony cd-player, K&N Filtercharger, Flowmaster 40 series + custom exhaust (no visible exhaust exit) BFG A/T 31"x10.5"R15 & Rancho RS5000 shocks

[82F100SWB]