Has any one got a clue as to what's going on with my 2002 Fx4 w/ a 5.4? Here are the symptoms: The vehicle feels like it is dragging, has no momentum and is plagued by really bad gas mileage. Feels like I am driving with 4000lbs of added weight. No codes show. But from time-to-time and often on the same tank of gas & same trip, the truck will suddenly come out of its problem and work like it useto. Now the truck feels lighter, has more power/momentum when you accelerate and coast. Even the steering feels lighter. To date, I have changed all of the plugs, new fluids, had vehicle examined by the dealer and others and installed new calipers and pads (x4). This has been going on for over a year w/o answers. Getting costly. P.S. only add on is a K&N air box, etc.

 

First thing I would do is reflash the ECM. Then go from there.

 

Partially clogged Fuel Filter? Bad Coil(s)?

 

How many miles? Fuel filter change may be needed.

 

Could be the fuel pump or clogged injectors.. But

 

Could be your fuel pump or clogged injectors..?? But I would try the filter first.

BLAST.. Sorry for the double post..

 

Thanks for reply. Not sure I know what the "ECM" is . . .

 

ECM = electronic control module

aka the computer

But i have never heard of "our" body style trucks needing to be reflashed

does it act like its sluggish no matter the throttle position? Have you done a visual inspection of the entire exaust system?
-Patrick

 

-It's sluggish 90% of the time and at all throttle positions. When it stops being sluggish is usually on the highway or down a lowng grade. Why??? The exhaust system looks Ok. Everything is new from the cat back. I replaced the fuel filter last year. I'm inclinded to think the problem is in powertrain - its as if the torque converter is not operating properly. Thanks for the inputs. PS things at 50K miles.

 

yah im leaning towards torque convertor now too, how many total miles are on the truck now?

 

Try two things.
Go into neutral to see if the drag slows the truck down quickly. If Yes the trans or drive line has somthing wrong.
While in cruise, apply just enough throttle to counter a very light application of the brakes. This should unlock the converter as another test to isolate if it is drive train or engine.
If you have a tach you shouild be able to see the rpm change when you let off the brake and the lockup reapplies by seeing the tach drop fast about 100 to 300 rpm +/-.
Ask dealer to refer to their OASSIS 614x00 chart 8 diagnostic info for in depth check on certain parts of the system such as the knock sensor circuit that might retard timing falsely etc.
Good luck, it can be found if looked for in earnest.