1st Gen Poor Fuel Mileage

[niburja]

Hello everyone!
So, I have a 94 XLT and my fuel mileage is terrible! First, it was 18mpg (highway) and stayed there for a long time, then it dropped to about 14mpg after a couple of years, and now after a year of that I'm at less than 11.1mpg (highway). At 14mpg I changed the plugs, wires, and oxygen sensors. It actually dropped to 12mpg! So, in the past 10 days I've changed the EGR Valve, replaced the EGR pressure feedback sensor, replaced the MAF Sensor, and had a muffler shop cut out the catalytic converter. It dropped yet again! Now I'm hovering at about 10.8-11.1mpg and I don't know what else to do. Could it be bad injectors??? Oh, I've also changed the air filter and the fuel filter to no avail.
Any ideas or knowledge from a similar experience would be appreciated.

 

[2stroke]

Not injectors, but don't just go replacing parts on a whim. Do a KOEO and KOER test, and come back with the results. There is plenty of data on how to do both without any equipment.

 

[Wolfie_85]

I gotcan ICM from a salvage yard to confirm or disprove whether mine had failed. Worked like a charm.

 

[natenkiki2004]

Having bought a 1994 recently, I decided to swap the ICM into my 1991 since it was getting poor fuel economy and I've changed a LOT of stuff (plugs, wires, temp sensors, O2 sensor, premium gas, synthetic oils everywhere...). After swapping, I filled up with gas. I'm now sitting between the E and 3/4 on my gas gauge and just passed 200 miles. That doesn't look very good.

I wouldn't put all your eggs into the ICM basket. It may just be how you drive or a engine that's wearing out. I think both are true in my case.

In your case, it could be the ICM. If you do mostly highway driving for long trips (10+ miles) and you get 10-12, that's pretty bad. Do the KOER tests and see what you get. If nothing comes back, maybe pick up an ICM at a junkyard and try it out.

 

[2stroke]

I just noticed you did all that within 10 days. Did you reset the computer every time? Reset the computer, put 2-3 tanks of gas through it, check for koeo codes, do a koer test, and then get back to us.

 

[niburja]

2stroke - Yes, actually I have been resetting the computer every time. I made an appointment today for next Monday to have a shop look at it and run the necessary tests because I don't have the equipment nor the time right now to research your earlier suggestion. Keeping my fingers crossed. I'll let y'all know what is said. Thanks everyone else for your input and helpful ideas. I appreciate it!

 

[natenkiki2004]

2stroke - Yes, actually I have been resetting the computer every time. I made an appointment today for next Monday to have a shop look at it and run the necessary tests because I don't have the equipment nor the time right now to research your earlier suggestion. Keeping my fingers crossed. I'll let y'all know what is said. Thanks everyone else for your input and helpful ideas. I appreciate it!

Skip the appointment, all you need is a paperclip and an ability to count to 10.

Use the bottom graph:
http://www.troublecodes.net/ford/

The connector is located behind the power distribution box on the passenger fender. Once the engine is warmed up, jumper the pins with a paperclip and start the engine and count the blinks.

 

[niburja]

Update

Okay, so I skipped the professional and did the KOEO and KOER tests myself. This is what I come up with:

KOEO - 336 code
KOER - 411 & 412 codes

I've already replaced the EGR Pressure Feedback sensor (new) so I'm not sure why I'm getting these codes???

Any ideas?

I've now run several tanks of fuel through it after all this and am still only getting about 12mpg on the highway. Is it possible that the new EGR Pressure Feedback sensor is bad and causing the poor fuel mileage?

 

[FR-425]

336 has two definitions:

1: EGR sensor circuit voltage higher than expected.

2: High exhaust pressure.

On number two this can be two things, you have the hoses to the DPFE reversed or the Cats are clogged or some other exhaust restriction.

On the 411 & 412 if you are not using a scan tool you will not hit the steering inputs or brake inputs at the right time and get both high and low throttle control faults.

This is to test the IAC for steering load and brake booster vacuum leaks.

Also for the low rpm check to pass the a/c compressor must be in working order. It uses the a/c clutch engagement to test the IAC. Same goes for the high rpm test. It uses the wide open throttle cut-out relay for the compressor to test the high end.

If all these things check out then it's just a false code caused by a bad run of the KOER test.

So if you do not have symptoms of stalling or crazy idle when you steer, brake or run the a/c you can just ignore those codes.

 

[niburja]

FR-425
Thanks for the tips. My catalytic converter was plugged so I had a shop cut it out a few weeks ago so I don't think that's it. Also, the hoses to the DPFE aren't reversed. They're a different diameter and only fit one way plus I paid special attention to how they came off. I just replaced the EGR Sensor so I'll test the outputs and see if it's just a faulty part or not.

I'll rerun the KOER test after I reconnect my A/C Compressor. It was disconnected.

Happy Thanksgiving!

 

[FR-425]

Happy Thanksgiving to you!

 

[FR-425]

Too early to rule out the ICM, with a failed ICM it will still run fairly well and even pass emissions but suck the gas.

 

[niburja]

Too early to rule out the ICM, with a failed ICM it will still run fairly well and even pass emissions but suck the gas.

Ha! I'm still figuring out how to respond properly to posts. (Hopefully this works how I think it will.)

I replaced the ICM already too, with a new part from O'Reileys. Not sure if I mentioned that in my earlier posts or not. Gas mileage still sucks!

 

[2stroke]

I find egr problems to be more of an idle, low speed problem, but you could plug the vacuum line to the valve to be sure.

 

[NPGuy]

Any updates on what you might have found?

 

[niburja]

Any updates on what you might have found?

No, not really.

I've replaced the EGR Valve, the EGR Sensor, the EGR Vacuum Modulator, the MAF Sensor, replaced the fuel filter, replaced the air filter, replaced the IAC Valve, had the catalytic converter cut out, changed the plugs, wires, and the o2 sensors, and now my fuel mileage is worse than when I started! I'm getting about 8 mpg in town and 10 mpg on highway. I've also disconnected the battery after every electronic item change to reset the computer and am now at my wits end feeling frustrated and defeated.

I don't really know what else to do???

Could it be the Fuel Pressure Regulator?

The Throttle Position Sensor is reading correct also, so I dunno anymore...

 

[2stroke]

What are you getting for fuel pressure?

 

[niburja]

What are you getting for fuel pressure?

I wasn't getting ANY pressure at all KOEO. I turned it over and, at idle, was getting 33 psi. I let it run for several minutes with no change. Then I shut off the engine and my pressure dropped immediately. So much that I didn't have to hit the bleed valve.

 

[FR-425]

Sound like it's time to pull the fuel rail and freshen up all the o-rings.

It should hold pressure after shut down. It may not hold all night but several minutes anyway.

The injector rebuild o-ring kits are cheap.

I'm not recommending this particular seller. Just an example of the kit. You will also need upper intake and fuel rail gaskets.

http://www.ebay.com/itm/Fuel-Inject...ash=item3aa44eff41:g:S08AAOSwqu9VEHH9&vxp=mtr

 

[2stroke]

It's a good idea to clean the injectors good too.