Hey Guys,
I just got my '01 SCrew Lariat with 119,000 miles on it (4.6 engine) back from the shop for a tune up. I had em put new platinum plugs in (replacing the original plugs), New Fuel Filter, cleaned the fuel injectors also, using a synthetic, not a full injector flush. But even after that i am still getting HORRIBLE gas mileage in the city, about 9 miles to the gallon. I got the truck used and the guy said he had kept up w/ all maintenece but had no records to show :-(. But i noticed the mileage problem immediately. It is starting to make me mad, especially w/ a fill-up of regular gas nearing $45 and i am just out of highschool, so i am poor. I just need any suggestions u guys may have to help me out. Thanks.

Also. . . i have read alot about iridium plugs. . . anyone have experience w/ those?

Trey

 

Well you have a heavy truck with a small engine and probably lead foot (most young guys do). 9 mpg in the city sounds right. My 98 ext cab 4x4 gets something around that. The older the motor, the less power which means you gotta apply more throttle for speed. Also I'm sure you run your AC which drains power. Welcome to truck life. I ended up buying a cheap little honda to drive to work and around town and kept my truck for weekends and etc..

 

you can make the engine get better mpg but it will cost $ intake and exeust are the best places to start you will see a increase but it will cost some denero, i get about 10 to 11 mpg on my truck with the bellow listed mods and i have under 20 k on the odomiter

 

9 is not acceptable.

i have a shop truck, 97 5.4 in a f250 with 140,000 miles and in the city with my lead foot it gets 12 to 13.

my 2001 supercrew 5.4 , it has a vortech s/c and also gets 12 to 13 city. ( i put the iridium plugs in and my mpg is the same.)

on a recent trip pulling a 5000 camper with gear i got 7 mpg with overdrive off and running about 62 mph.

thing i would check (if the motor seem to be alright)

tires, alignment and possible brakes dragging.

 

I didn't see anything about the air filter being replaced during the tune up. Not sure how much it will help but you never know.

If something small does not fix your problem then I would think it is something more complex somewhere in the motor or tranny.

 

how is it running? is it running like a champ nice and smooth? or is it sound like it is missing or have a bad idle? is the check engine light on? any more info could help us figure this out

 

Are the tires the stock size, or does it have larger tires and the odometer has not been corrected?

As mentioned, dirty air filter, bad alignment, dragging breaks will kill mileage.

Also, a bad tank of gas will do your mileage in. Try filling up at another station.

And in hot, humid weather your truck is going to run richer, plus you are likely to be blasting the AC.

Maybe the EGR is clogged and should be replaced. Also have seen some posts about the IAC needing cleaning.

IMO, a cold air intake and iridium plugs are not going to make much if any mileage improvement.

Good luck with it - 9mpg does seem awfully low.

 

You live in Houston, enough said. I have a 2000 with a 5.4 and get about the same in city driving conditions. There is not much you can do about it with the heat and humidity. Get use to it.

 

Have the O2 sensors ever been changed. If not change the front two. It will perk up your truck and you will need less pedal to get going. If used wisely that saves gas.



Regards

Jean Marc Chartier

 

Sounds like you are getting fuel with 10% ethanol alcohol added.

My '99 5.4L auto gets 8-14mpg driving with ethanol blend - When I get out-of-state non-ethanol I can get 16+mpg highway, usually with premium almost 18mpg highway driving (Missouri & points farther south gas)

Remember they use ethanol to raise octane so often the mid-grade gas will be alcohol blend. With the recent gas price boost I've seen out-of-state 89 octane blend cheaper then the 87 regular!

Minnesota has MANDATORY 10% ethanol, we are at the end of pipelines, zero petroleum reserves here and get all sorts of exotic blends that aren't worth squat. But if the Arabs turn off the taps we will still have *some* fuel resources available. I use only BP here, just recently switched from Mobil - better power & less vibration...

EDIT: Oh ya - Oxygenated gas for Urban areas, subtract 10-15% milage regardless of Ethanol or not..

 

Air filter, PCV valve, and front oxygen sensors could all be problems affecting fuel mileage.

 

that was good info wabbiteer, i didnt know that

 

APT

How do pcv valve affect gas milage?


Marcos

 

I have heard that from a few sources, specifically Haynes repair manuals for vehicles I have owned. I'd have to do some research to learn more specifically about why, but there are many web sites that can explain it better than I would. It affects the intake manifold vaccum.

Look at me for the first Google hit.

 

I'll change pcv this weekend!

Marcos