Have been chasing an intermittent "very high idle" problem and previous codes show 332,181,327. found and corrected some vacuum leaks which has helped some. At that time, MPG @ 19 per gallon. When returning home, parked and forgot and left the headlights on. Came out to start and of course, the battery was dead. Jumped started using "booster box" and now, have no high idle problems at all. Now, only code I am getting is 172, but worst thing is, my MPG has been cut in half!! Can almost see fuel hand moving down as driving along! Can't figure this one out. Oh yea, of all of the sensors previously tested while chasing the "high idle" problem, I was getting below the stated voltage test for the MAP sensor. Have not changed MAP sensor at this time. This is a 95 f150 XL 4x4 5.0 with 135,000 miles and all codes read were KOEO. Hope some of you guys have some ideas. I don't have much hair left to pull out!!

 

Wow, you were getting 19mpg with a 302 4x4? I wish I knew what was causing your sudden mpg drop, but that's the most impressive mileage I've ever heard for that combo.

 

Are you getting the proper signal voltage going to the MAP? If your battery went completely dead, the KAM would have been cleared and would rebuild from scratch. So you would be starting at a default fuel trim (rich) and on your way to the strictly enforced 14.68:1 which is knocking hard on the door of lean, which is why it doesn't take much to put it over into a lean condition. If the truck isn't running long enough to reach operating temp., doesn't reach op.temp.(Thermostat temp too low) or doesn't know it has reached operating temp (ECT bad/ will code on KOER scan) you can't buy one more mile over 11 mpg.

 

The reason you don't have the high idle issue anymore is because when you killed the battery that cleared the codes in the computer......so you may have thought you leaving your lights on was a dick move but it ended up helping you...well till your mileage became crap. I gotta think on this.brb

 

not un common...my buddy has a 96 302 4x4 with a MAF and gets 22 easy...

 

I get 11 in my 300 2wd..............................................

 

I get 19 city and 24 highway in my 95 300-6 2wd 5 speed...

I was getting 12 when I bought it...took alot of tweaking to get it where it is now and I am going to try finding another EFI head and go have it ported and filled with larger SS undercut valves..that should get me to 26...

 

The computer has to relearn when the battery is disconnected so you might get the mileage back when it does.

 

Damn.. What all did you do?

 

find my thread and you'll see..there was about 5 of them...