Hello,
My truck has approx. 60k miles on it. I purchased it new and it hasn't ever had any mechanical issues. I noticed about 2 weeks ago that my engine was having a slight "shutter/hesitation" when idling. Soon after that, the acceleration was a little "sluggish". Then, I noticed the mpg going down quickly. My experience led me to replace the spark plugs. I did that 1 week ago and the engine idle/acceleration has returned to normal, but the fuel economy has not. My normal commute is all highway so I drive around 65-70 and average 17.5-18 mpg. This morning, it was 65 mph and averaging 13.4mpg. Now, I know someone is going to tell me, "You need to manually check the fuel economy. Maybe the electronic gauge is wrong." I know how much gas my truck uses to drive from home to work for a week. I am literally burning thru twice as much fuel as I have for the last 4 years. Any advice is greatly appreciated!!!

 

What brand and model plugs did you use and what gap did you use?

Disconnect the battery for 20 minutes to reset the PCM so it can relearn.

 

Autolite iridium (something). I don't remember the model. I set them to .030

 

Seems to me I've read about timing chains needing replacement before many miles?

 

Autolite or Motorcraft? You *should* have used the OEM Motorcraft (SP534). Change them every 40k. Replacing the coil boots is also recommended.

 

I disconnected the battery for an hour yesterday. This morning, no change... at least, not yet.

again, to address the "coil boot" and "timing chain"... the truck idles and runs really great. Just getting terrible fuel economy.

 

May need to take it to a dealer and let them hook their computer to see what it can find. Running rich is not good for the cats or the engine.

 

Roadie- Thanks for your advice. I was telling a buddy that I went to the Forums to eliminate all the simple stuff before dropping it off at the Ford ER.