My 2003 F150 was sitting for about 8 months. Got the starter fixed which before it was sitting was the only problem. Now when I shift gears it rumbles and doesn't have much power or pick up - it feels like being in fifth gear at 30 mph. It's worse when going up an incline. So far I only put gas and fuel injector cleaner in it.. no improvement.
Thank you for any input.

 

I would suspect the 8 month old gas.
Additives don't bring old gas back to full heat content.
Pump it out and replace with new.
Gas begins significant deterioration at about 9 weeks.
Good luck.

 

Forgot to mention that my husband changed the spark plugs only (not wires)

 

The gas was very low and filled to a little over half - should it still be drained or should I fill it all the way up maybe?
Thank you...

 

Might want to change the fuel filter also if it hasn't already been done.

 

The next thing is to look at live data with a Scanner to see what is going on.
Without a clue it's tough to get it cleared unless you have some luck.
Severe lack of power can be old gas that has very little ability to make any heat from combustion, ignition timing is too retarded, brakes dragging etc.
You can even put to much additive in the gas.
When it's not obvious and there are no codes, you have to investigate deeper.
Good luck.

 

Will do - Hopefully it's that simple! Thank you..

 

Which engine do you have?

 

Not sure- I'll have to check.. 4.something

 

Well, if it's a manual transmission, it's either a 4.2 V-6 or a 4.6 V-8.

 

It's a standard

 

Okay, but is it a 6 or 8 cylinder?

 

It's a 6 cylinder