A few months ago my milage dropped from 18 avg. down to 15.5 avg. This seemed to happen over night, not gradually. All service is up to date and the truck runs fine...unloaded. When pulling an 8000lbs load, the fan runs constantly. I also noticed that the power is way down, struggling to get up hills that used to be no problem. The coolant temp. seems to stay between 192 and 200, loaded or not. The power loss is only when pulling.

I did add an Ultra-guage and found something odd. When the truck is first started, all gauges come on. After 5-10 seconds, I get an error code on the MPG, Intake air temp. and manifold pressure. I also get "no fuel sender found" on the trip portion of the gauge.

I recently pulled the plug on the EGR valve and the truck runs better. I haven't tried pulling yet, but I have more throttle response and more power. I have driven it this way for about 400 miles so far with no CEL. That doesen't seem right. Do I have some kind of FICM or PCM problem?
The dealer did the "service drive scan" and said no problem(codes) found.

The truck is a 2005 F250 CC 3.73 with 174,000 mi.
Any ideas?

 

The "no fuel sender found" is a red flag.

You likely have a weak fuel pump / module / or connection.

Disassemble the back VFCM wiring, make sure there is no corrosion and good contacts and no wire breaks.

Verify operation of fuel pump at high output --- if there is a bad connection, it would give low pressure at high output --- and intermittent fuel pressure weakness is the killer of mileage at high engine output / bad fuel consumption as fuel pressure plunges

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Then do something simple.

1. Change all filters and oil.

2. Check fuel pressure / verify good

3. Dump in Dieselkleen / Cetane improver (2x recommended concentration)

4. Plug the EGR back in

With it out, it can go to limp mode with poorer mileage without setting a code necessarily.

5. Verify EGR operation (partial failure will not necessarily set a code, but kill mileage).

Even better, replace EGR with new one for test

6. Italian tune-up with all of above done

7. Recheck mileage.

8. The "no fuel sender found" is a red flag.

You likely have a weak fuel pump / module / or connection.


Finally, try my trick of disconnecting the fuel heater.

 

There are a few possible things going on that I see. It appears there is some sort of electrical problem. Not only the fuel sender error (which has nothing to do with the fuel pump, by the way), but the other missing data indicates maybe a module communication problem, or possibly symptoms of bad grounds. I'd start here with the bad grounds. Also check all your fuses with a test light or meter.

The fan running is another concern. Was the fan running all the time before or after you disconnected the EGR? Your coolant temp is not high enough to trigger the fan. You need to know what your oil temperature is. A plugged oil cooler will cause very high oil temps, will trigger the fan and can put you into a limp mode.

Here is another thing I find odd. You said you disconnected the EGR, yet the dealer found no codes. Disconnecting the EGR will set codes. So either the dealer didn't scan for them properly, or the above suggested electrical problems are preventing them from being transmitted properly.

Those are the things that stand out to me.

 

Thanks for the reply. All fluids/filters are up to date. I have been using Dieselkleen every 1-2 tanks, sometimes every tank. The stock fuel guage on the dash seems to work fine. Where is the VFCM wiring? Could another sensor cause the truck to go into limp mode and not set the light? Would too much EGR cause the intake air to heat up and run the fan?

 

David,
The fan was running before I disconnected the EGR. Also, the dealer did the scan before it was disconnected. I did the FICM test and got 48.5v.
Thanksfor the help.

 

I go with dcham that something is not right.

Not setting codes does not mean it doesn't go into limp mode.

If you can see the "freeze frame" data, you will find it takes a lot of "trips" to have a code set.

In the mean time, if something is not right, it can go into limp, and then not be happening enough to go into limp permanently and set a code.


Take dcham's idea ---

a) check for codes with a real good scan tool (AE)

Watch for what it says when you are actually experiencing the problems ---- log the data.

b) measure EOT/ECT differential and see if you are within spec

c) bad ground on VFCM would do it. (under truck)

Oh... fuel gauge is very "damped" and will not respond to an intermittent short in the sender / loss of communication.

That speaks to a wiring / connection / circuit fault.

 

OK so your FICM is good. That eliminates that problem. Also probably eliminated is the issue of codes being missed.

I'm still concerned about the missing PID's. There is a reason that they aren't there and whatever is causing it could be causing any number of difficult to identify problems. I'd do a careful check of your fuses and check as many grounds as I could find. Check the main battery grounds to the engine and look at as many engine to frame grounds as you can find.

I would also still want to know what your oil temperature is at normal operating temps.

 

The Ultra-gauge dosen't check EOT, so I'll probably have to take it to the dealer for an extended "Ride and drive" scan/evaluation. I will check grounds and fuses myself. Thanks for the input.

 

The missing gauges on the ultra-gauge are the MAP, Intake air temp, EGR flow, Baro. pressure. Anyone know where these come from? I assume that all of the sensors work because the give values for 5-10 seconds before going to error. Do these sensors report to the FICM or the PCM? Could the FICM still have a problem even if it shows
48.5v? If I turn the key off and then turn it back to run, without starting the engine, the same thing happens...numbers for 5-10 seconds and then "error".
Thanks for any ideas.

 

Try reset all the computers.

 

All of the sensors you mentioned connect to the PCM, as far as I know. Although EGR flow is calculated from the values of other sensors.

I'm actually kind of wondering about the reliability Ultra-gauge. I can't say I've ever even heard of that. That's just a feeling though.

I'm leaning a bit toward an oil temperature problem, myself. I think you can feel pretty confident in the FICM, assuming that voltage holds through cranking and starting and while the vehicle is running.

Resetting the computers wouldn't hurt. Just disconnect both batteries for 10 to 15 minutes.

 

That will not necessarily reset the computers and is not compliant with the recommended procedure to do a proper job.



Most of the boxes have capacitor(s) that keeps a charge on for as much as 30 minutes of "power off", and by doing so, any glitches as well as memory is preserved.


In order to discharge the capacitors and ensure a bona fide reset, the recommended procedure is to disconnect the batteries, then turn on the headlight (dimmer on max) to ensure the capacitors are discharged by waiting at least 10 minutes and preferably up to 30.


You will know if the boxes discharged if upon the next "start", the transmission shifts roughly as it has lost its memory.


The proper procedure to reset the computers is in link below.