coolride

These 4.2l engines have been around a while now. Anybody have any good ways to improve MPGs? I have a 2003 f150 sport 4.2 5spd 4x4. All stock. I drive it 90% highway. I get 15mpg at best. Which I think is a joke honestly. I've driven it like a little old lady on up to driving it like I stole it, the MPG doesn't change much on this ride. I honestly thought I'd get closer to 20 with it. But I can't get close to that. I did the air filter housing mod, gotts mod maybe ? it didn't do anything in my opinion, maybe it did but nothing noticeable.
The engine is a reman, it has only 40,000 miles on it. New upper intake grommets and gaskets, new plugs,wires,fairly new cats, no engine codes, runs good. Truck is stock, stock tires and they are all seasons, nothing aggressive to eat up mpgs.
Looks like 15mpg is the norm for these rigs. Hoping someone had a way to get some real results. Looks like if we can't squeeze decent MPGs out of these 4.2s, there isn't any point in buying one. The 5.4 and 4.6 get the same MPG with more nuts.

ametzker

The best I've got is 19.6 mpg. When I pulled a boat last week I still got 15+. I don't have any cats and I also deleted the EGR system. My intake butterfly valves are also modified to stay open all of the time. On average I get 17-18mpg mixed driving.

Michaelval

I have a 1998 f150 4x2 with a K&N CAI and Gibson catback exhaust and I get 20mpg on average. I have calculated this many times and with many road trips. I just drive normal. I need to run a can of seafoam through the intake to clean up some stuff. I would imagine it will run a little better after that as well. I plan on adding shorty headers soon and my truck has 126,000 miles.

coolride

So you guys are getting much better mpg than I am. I haven't made it above 15, and I drive 1 mile in town and 17 miles highway twice every day. Almost all on 65mph road. I've tried driving the speed limit and babying the gas pedal, and I drive it like normal at 70-75, sometimes 80...lol. But the mpg doesn't vary too much, it just pretty much consistently sucks. My truck is all stock. The only thing I think is odd about the truck is the engine doesn't idle smooth. It isn't misfiring or anything, just not smooth. I replaced plugs and coil pack. That did nothing for it. Plugs I took out looked fine but I swapped them out anyway. Maybe I have a funky injector?

ametzker

The intake egr ports clogging up are one of the biggest problems these engines have. It may account for some of the idle issues and poor fuel economy. This is the biggest reason I deleted the egr that goes into the intake manifold. When I rebuilt the engine I could see where it was a huge problem area and I didn't want to be dealing with that every year. Seafoam may work if they aren't very clogged but when they get plugged up the only fix is taking the intake off and cleaning it the right way. I had to use a pressure washer on mine with a needle tip. gnarly stuff.

coolride

I guess if I have that problem its gonna die with it. lol I have already replaced the engine. I had the upper intake off one more time after that. To do so, I have to remove 1 motor mount because I can't get intake cover off without doing that. It makes a fairly easy job a pain in the butt. So unless something explodes I won't ever touch the intake again! It involves way too much swearing. I have read where other people can get the intake apart with just enough room. Just my luck!
How does your truck run with the intake butterfly propped open? People say low end would suffer. Is that true or does it run good that way?

ametzker

Yeah the intake job is something I would not want to do with the engine in the truck. Although I think the 4.2 is way easier to service than the 4.6 or 5.4 I tried to do ever conceivable upgrade and/or replacement of parts/sensors when I had the engine out. As far as low end I never drove the truck when the butterflies were working as I bought the truck in broken condition. It pulls great down low so I don't think I'm losing bottom end but I can see where it would make sense. I think I'm going to install one catalytic converter back in it because right now it doesn't have any and I think the engine would benefit from a little backpressure.

coolride

I think I have found the perfect solution for my Ford. I'm going to sell it.
It seems pretty much all full size trucks are getting around 15-17 mpg until you get into fairly new trucks, then you can get closer to the 20's.
If I have to drive a 15mpg truck, it may as well be sporting a v-8. My '03 f150 isn't a bad truck, I'm just ready for something else. I don't want another truck of this style, and I don't much care for the newer ones. Gonna have to swap brands. But don't worry Ford fans, I won't go chevy, not happening! I can sway a little but not that far!! lol

coolride

Things have changed, looks like I will be keeping this ride for a while longer. I may be relocating so no sense swapping vehicles here and paying DMV fees to just do it all over again in another state.
So I started getting a PO161 code, bank2 O2 code. Also found the source of my random evap codes too. Gas tank had a patch on it from the PO. I wasn't aware of it, until it began leaking. So tank fixed now. And I had an O2 sensor already(original engine had O2 faults, long story) so I replaced the right rear O2 sensor and cleared the codes. Lets see if the CEL says out. It had been saying out for a long time, then I started getting Evap faults like gas cap, and the 161 code. May all be related? Either way, tank is good now and sensor is new. Maybe the old girl will be OK now.
Working on a ****** truck, with a carburetor. I can't wait until it is running!! I am done with this Ford with the computer issues I've had! At least now she runs good. Hopefully it stays that way a while!

Tredeh

The good old 4.2.
When I was driving 80 miles of highway 5-6 days a week (60 mph, hilly terrain) I averaged 21-22 mpg. Thats with a 5 speed and 3.55s on a regular cab swb
I know a guy with an identical truck, but his is an auto. He drives roughly the same amount of highway miles I do but averaged 18. He doesnt drive it easy though.