fuel economy dropping

[Nhaz]

Okies. So as the title says the fuel economy on my truck is slowly getting worse. Im down to 400k on a tank and maybe slightly under.

I got out my obd1 module and looked for codes.

My tester showed as usual code 22 for a MAP sensor that doesn't exist on that truck and as far as I can tell never did.

I'm no expert on any of the obd systems so i re read the instruction manual for the OBD tester. it has 4 or 5 separate tests its capable of running. I was working my way through the various tests when i got to the KOER test.

The manual for the tester clearly says the module will first report how many cylinders the vehicle has by blinking the light on twice for 4 . 3 times for 6 . 4 for 8 and 5 for a 7,3 diesel.

The light blinked 2 times. and stopped. nothing else at all. waited the 20 seconds it says to wait plus another 30 for good measure.

I reran the test and got again 2 lights. Now i dunno about you but when I have a 4 liter 6 cylinder and the obd says theres a 4 cylinder I start scratching my head.

I stopped trying to complete this test and I am now at a loss at what to do next. Not to mention slightly confused =>

oh and BTW the engine runs fine lots of power and you can smell some unburnt fuel. Is it possible that a O2 sensor is misreporting? I mean i thought these things worked or didn't.

 

[Nhaz]

Anyone at all?

 

[nooberiffic]

I got nothing. Its throwing a 4 cylinder ID? Hmmm, random guess, is the computer the correct one?

 

[creepinjeepster]

Reset CPU by disconnecting battery for more than 15 min and reconnect. See if it still registers as a 4 banger.

 

[Nhaz]

I'll do that in the morning. The computer Came from another vehicle. But it was a 91 4.0 v6 ranger, as far as I can tell its a identical truck. Other then it being red and mines green =>

 

[creepinjeepster]

Yes, should be identical. 93 is when they started the 2nd generation models.

 

[Nhaz]

As life has it I wasn't able to get time to reset the computer till today. which i did. and the obd 1 system reset correctly and now reports the truck as a 6 cylinder with only the OK code of 1

 

[BUGNUT]

400km to a tank is pretty good in my books. My Ranger 4.0 gets 350-375KM in the winter and 400-425KM in the summer. Thats for a 65 liter fillup.

Want good mileage buy a Focus. Mine gets double the Rangers mileage.

 

[Jspafford]

Winter mileage is worse. The wife's Sport trac goes from mid teens in the summer to 10-12mpg in the winter.

4.0 SOHC...

Nature of the beast.

 

[Nhaz]

My economy Last winter was better by 50k a tank. Which is why I was looking for a problem.

 

[mailboxman]

Hey Nhaz--i was just leafing through the forum before work this morning and was wondering---do you still use the toggle switch to disable the IAC???? If you are-could switching it off after warmup be affecting timing? just a thought

 

[Nhaz]

I discovered why my IAC didn't function right last July and corrected the problem by replacing the EEC-IV OBD-1 computer. This also corrected my lack of overdrive at the same time.