5.4L in a SUPER DUTY

[The Hunter]

I have a '99 with a 5.4, 5 speed. 4.10 gears in a SC 4X4. I love the truck . It has 43K on it & runs great. Have taken it way too many places off road it should NEVER have gone. But towing my 8Klb travel trailer in the mountains??? Need a Power Stroke!

It never got outstanding mileage. Best on the road was 17mpg empty @70. Towing from Phoenix to Flagstaff was 6.3 mpg and was flat on the floor all the way up there! It tows but be prepaired to spin the engine to 4500 for 10 minutes or so at a streach. The 5.4 has a ew K&N intake system & a Flowmaster 5000 series freeflow muffler to help out.

My next one will be a powerstroke with the torqueshift auto tranny. Dont really care about mileage but hate to push an engine so hard.

 

[ibsmurf]

5.4's are great if you're not towing really heavy very often. If I didn't own my 5er, I'd probably have one instead of my V-10.

 

[TTLS]

I get 10 MPG in my Screw. And it's a 1/2 ton. Something is wrong, but I don't know where to start looking. It has new plugs, but maybe some iffy coils?? Fuel filter perhaps?

 

[Mastertech]

Originally posted by TTLS
I get 10 MPG in my Screw. And it's a 1/2 ton. Something is wrong, but I don't know where to start looking. It has new plugs, but maybe some iffy coils?? Fuel filter perhaps?

How about getting a scan tool hooked up to it and taking a look at the data in the pcm and see whats going on.

Thats where I would start.

 

[Mike]

Originally posted by TTLS
I get 10 MPG in my Screw. And it's a 1/2 ton. Something is wrong, but I don't know where to start looking. It has new plugs, but maybe some iffy coils?? Fuel filter perhaps?

I bet you have an O2 sensor out, I think there is one (or two?) in the exhaust either pre or post catyletic convertor.

 

[Mike]

We just bought the ole lady a used 03 Expy, its got the 5.4 in it. Are there any handy mods I can do to it she wont know about

I wanna be able to the tires

SCMT must make a tuner for the gassers, has anybody had any experience with one?

I can see it now, Im in for a heap of trouble if she finds out I'm trying to bomb her new ride

 

[Mastertech]

Originally posted by 95_stroker
I bet you have an O2 sensor out, I think there is one (or two?) in the exhaust either pre or post catyletic convertor.

Should be 2 upstream and either 1 or 2 downstream O2 Sensors.

I doubt he has a bad O2 sensor.
The MIL light should be on if it is bad.
OBDII systems keep a pretty close eye on those O2's.

 

[Mike]

Only reason I threw that out there is that I had a co-worker with a 5.4 in his wifes rig, was getting 18 mpg pretty regular with it then alla sudden it dropped to that 10-12 mpg range, they found a bad O2 sensor. So they replaced it and it cleared the mileage problem right up. I do not know if it threw a CEL or not, but he didnt mention that it did, he just said the mileage mysteriously dropped WAY off for an unknown reason. Once they had the codes read they knew it was a bad O2 sensor.

 

[TTLS]

CEL came on the morning after I did some drift bustin' a month back or so. Ran like ****. Replaced all 8 plugs, dried the coils out, cleared codes, seems to run okay now but gas milage sux. I'll check into the O2's. Are they the same so I can swap 'em out until I find the bad one? Would a bad coil cause bad gas milage, yet no detectable misfire/poor running/stumble condition?

 

[Mike]

Have you been under the vehicle since the drift busting incident? Is that near about the time the MPG took a dive? Might crawl under there and take a look see if anything came unplugged. I dont think you would see a coil affect MPG's without seeing it affect smooth running. Coils to my knowledge dont sorta fail, they either put out said voltage or they dont.

 

[Mastertech]

Originally posted by TTLS
CEL came on the morning after I did some drift bustin' a month back or so. Ran like ****. Replaced all 8 plugs, dried the coils out, cleared codes, seems to run okay now but gas milage sux. I'll check into the O2's. Are they the same so I can swap 'em out until I find the bad one? Would a bad coil cause bad gas milage, yet no detectable misfire/poor running/stumble condition?

And now we know the rest of the story..
If the MIL came on then it very well could have an O2 Sensor problem.

TTLS, the upstream O2's will be different than the downstream ones.

You really need to get a scan tool hooked up to that truck and see whats going on for sure.

Run it by autozone and they will pull codes for free.

 

[TTLS]

What codes will I be lookin' for and will it tell me which one is toast?

How difficult are they to replace?

 

[Duke]

Originally posted by Sbrem
Yup, thats what mine is. Works great with the 6 speed.

Stephen

Stephen,

Great looking truck. I love the XL trim, even though it's the plainest level.

I like the argent grille & bumpers.

 

[Mastertech]

Originally posted by TTLS
What codes will I be lookin' for and will it tell me which one is toast?

How difficult are they to replace?

Did you get the trouble codes yet.


If it's an O2 Sensor they are easily replaced..

 

[Sbrem]

Originally posted by Duke
Stephen,

Great looking truck. I love the XL trim, even though it's the plainest level.

I like the argent grille & bumpers.

Thanks Duke. I like having the sealed beam headlights because you don't see many trucks with them. At least around here even most of the XLs have the upgraded lights.

Stephen