Hello again everyone... A couple days ago I had an employee help me change out my spark plugs, earlier this week got an oil change. Since the plugs were changed (about 75 miles driven so far give or take) it seems like my gas is going down faster. Has anyone got an idea why this might be? Also, since the plugs were changed, my CEL is back... P0440 again. Any insight would be helpful.

 

Check the gap mabey? Or that the wires are snug/pushed down all the way. Mabey you need new wires/rotor and such.

 

what kind of plugs did you put into the truck? champion copper core plugs are the correct plug, anything else can cause problems (correct gap is .040)

btw the 4.7 does not have a cap/rotor or wires

 

Sounds like a coincidence. The code is due to a leak in the evap system, which could kill your mileage, I suppose...

 

Thanks for the replies... yeah, the evap code is one of the first reasons for me joining this forum several months back, then it just disappeared. But it did stay on whenever I'd turn on the D to prime my fuel pump before starting it, but would go away after starting up.
Yes, plugs are Champion copper cores gapped @ .040 - crazy thing though, looking at the old plugs, they were gapped @ .070!!! But it was just today I was noticing on the way home that I dropped about 1/8 of a tank and didn't even go more than 15 miles. That equates for about 5-6 mpgs! I was getting an avg of 15.7 since my homebrew CAI install a few months back.
As far as the evap code I think I might have to revisit the piping under the driver's side. But also, there are a couple lines on the driver's side by the airhat above where the plugs go that seem loose now. One has a green **** of some sort. Are they a part of the evap system?

 

The gas gauge may not be entirely accurate. How does it run. Better, worse or the same prior to the new plugs?

 

1) yes those lines under the hood are part of the evap system (the green cap is a test/service port iirc)
2) the gas gauges in these trucks are EXTREMELY INACCURATE (hell when i can turn the truck off and on again after driving and drop 1/8 of a tank there is something not quite right), i usually go my mileage for filling it up
3) the CEL is always on when the key is on and the engine is off, its the way the trucks work

 

I'd say this applies to every car with a CEL, I've never seen one that didn't come on until you started the engine.

 

Chris, my D seems to be running better, I'm not noticing any stumble at idle so far like I was before the change.
Shrps, what's the avg max mileage with these trucks? I believe it's a 25 gallon tank, and of course you know I have the 4.7l 4x2.

 

To clarify, when I turn the key to "on", before starting, as all the different indicator lights turn on then off, the CEL remains by itself. Is that normal?