Home Forums Hunting & Shooting Hunter's Campfire Truck power and mileage declining

I’ve got a 2012 F150 with 5.0L V8, 3.73 gears, 6 speed auto trans and last year was averaging about 18 mpg according to the trip computer on board. I’m now getting into the 15 mpg range and it certainly feels less powerful and maybe a little busier on the trans to maintain speed on hills. The only changes I’ve made since buying it in 2015, and it was stock before, are new tires and a livestock rack. It’s possible that the rack may weight 100-200 pounds and may add a little drag, but man I sure wouldn’t think it would cause a 30% drop in mileage or power.
One other issue, when I started worrying about this in he summer I discovered the clips were gone from the air box when I put a new air filter in. I have them now, but could dirt have gotten above the filter and into the engine maybe?

Any ideas to improve this? Oh yeah 87,000 miles

First guess would be brake drag or emissions issues (the latter should set a code).

4x4?

Dirt would certainly destroy piston rings and valve seats. I would take it to a reputable mechanic and do a compression check on it . You might also want to test the oil

I'd start by cleaning the throttle body and MAF.

One quick fix for many of our vehicles has been to hit the MAF sensor with some of the special cleaner spray. I've seen it fix hesitation, lack of power, & stumbling, and I've since taken to cleaning 'em every 30K miles or so, just on principle.

Just spitballin' here, but if the missing air box clips let unfiltered air through the system, that sensor may have gotten dirtier, faster, and it might be giving the computer bad info that causes it to dump more fuel into the system.

Beyond that, new plugs 'n wires probably wouldn't be out of place on a 2012 with that kinda mileage.

FC


edited to add: I took another look at your location - oxygen readings would be even more important in CO, since you have less to start with. I'd roll the dice on a $8 can o' spray. The process itself takes < 90 seconds, plus maybe another 60 seconds for the MAF to dry before you stick it back in.

Has there been any boost in the alcohol content of fuel?

Winter fuel and tires will both make a big difference in mpg. I loose ~3 mpg in the winter with snow tires and winter blend fuel.

Did you change the little trip computer from fantasy settings to real world settings? Just asking because I've never done actual math and been happy with the vehicle computer.

I am with sock puppet on the throttle body. My GMC Sierra 1500 had the same symptoms. Cleaned the throttle body and wa la, back to normal operation. Easy to do on mine and the cleaner was less than 10 bucks. Definitely worth a try. Instructions for mine were readily available on the web.

..............................Any check engine light on??.........If not, then you nevertheless should take it to your nearest Ford dealer or favorite mechanic who can search for any trouble codes to see if any trouble codes pops up........Another possibility might be a bad catalytic converter....Your livestock rack would not cause that kind of drop in power and mileage.

Unless your air filter housing had large gaps because the clips were missing, I would think that it would not be likely to be causing your problem......

Try putting some premium gas conditioner or fuel system cleaner in the tank just before you fill up. Doing so will help clean the valves, plugs and combustion chamber. And then see if you notice an improvement. Btw, you should be doing that about every 4 to 5K miles anyway to keep the fuel system,valves and combustion chambers as clean as possible.

If you do notice an improvement, you may want to repeat that process one more time. Then see what the results are afterwards when the conditioner has been used up.

I would for sure though have your catalytic converter or converters checked out.

Lastly and the worst possible scenario might be an internal trans problem. However, if you have no shifting issues on level ground then your clutches inside the trans should be OK.....

Is your idle smooth??? Another possibility could be an ignition coil to one of your cylinders.
MAP sensor that controls the air flow signals to your computer could also be the culprit......

First things first.......See if there are any trouble codes and put in the gas conditioner....

yep that would be the first thing I would place blame on. Your area may have recently switched over fuels. Also tires make a big difference. 2012 5.0 with 6 speed. IMO you have one of the best sorted trucks. should last a long time. I wouldn't be eager to part with it for a new ford I can tell you that, unless you are high mileage.

Catalytic converter might, could be an issue.

My first thought too but at only 87k?
My wifes Caddy had that problem but it had more years and mileage on it but it acted like the OP's truck, gutless and bad fuel mileage with no codes.

Maybe the 100K mile spark plugs, didn’t make 100 K miles. Along, with some of the previously mentioned items! memtb

I'm going with something dirty plugged up in the intake (MAF, throttlebody, etc). Plugs and wires might be getting old. Also are the tires the same rating or do they have a higher load rating? Takes more power to turn a heavier tire.

Change the plugs first. There shouldn’t be plug wires on one that year, most likely it’s got individual coils.

Tires, did you change the size?
Big change in tread pattern?

That was my thought as well. My 98 Explorer has in the last month gone gutless and gas mileage dropped from 16 to17 in town to 14. It has a V6 and only 56K miles. It was my wife's car until she passed. I had it emissions checked yesterday and it passed just fine. I've also noticed my 2015 F150 3.5 Ecoboost has not been quite as peppy. It only has 5,2K one the odometer. Makes me wonder if they've quietly slipped that 15% alky into the gas.
Paul B.

Thanks all, this has been a steady decline over the last year. Had never heard of cleaning the mass air sensor. I’ll start there and really no harm in replacing plugs and wires. Compression test could be insightful too.