After fixing my fuel pressure issue and replacing my 02 sensors, I am finding that I am still getting really bad fuel economy and loss of power, if not worse than before. Today when driving to school, it had to downshift to make it up the small hill by by house. Last full tank of fuel (prior to the work done) I was able to get 215 miles before the gauge hit 1/4 tank, currently I have done only 180 miles and I am below 1/4 off a full tank of gas.

Whats strange is it isn't throwing any codes. All of the sensors that I can pull a reading from with the ultra gauge are normal too.
What is going on here?

 

Maybe a bad cat? Could of blown through and be blocking the exhaust system? Without knowing more that's a wild stab in the dark but symptoms sound similar to mine when this happened.

 

I replaced the cats about a year ago. It would be hard to believe that they are bad already. What about the throttle position sensor? I noticed mine reads 12.5% closed, 94% open on the ultra gauge. I've heard before it should be at 5-7% closed, but I can't confirm that it is causing these issues. What's the deal here?

 

You have normal ug TPS reading

Last fuel filter? Fuel pump?

Is the vacuum line on the fuel pressure regulator?

Checked the MAF?

In morning cold engine key on does the air intake temp close on ug to ambient temp?

 

-Fuel filter was replaced about 2 years ago.
-Vacuum line to regulator is new (replaced regulator with OEM one about a month ago).
-Cleaned the MAF back in November, good g/s reading from UG.
-Intake temp is the same as the ambient temp on startup.

 

What is you idle fuel pressure?

Have you checked and cleaned your grounds? Sounds stupid but I have found it fixes electrical gremlins on mine

I would do a new fuel filter, cheap and can't hurt

Last tune up?

Clean throttle body and IACV?

Pcv is clean and good hoses?

Voltage output from alt.

Possible bad gas, water in it?

Unplug vss see if it changes ?

I am thinking someone had this problem recent can't recall the solution

 

Tire pressures? Mine makes a huge difference in mileage between running at 28psi and 40psi.

 

If it is not throwing codes still I strongly suspect the MAF. I have swapped a suspected bad MAF for a known good one and the difference was immediate, and I was not getting any codes with the suspected bad MAF. I returned the good MAF and got a new one and haven't had a problem since. I was getting about 9 mpg with the bad MAF.

If you were getting codes for misfires I would suspect a vacuum leak or cats. Does it idle well?

I've had these problems and the last symptom, as I fixed things, is exactly as you describe. Do you know someone with a well running Rover that will let you borrow the MAF? The difference is immediate if that is the cause. There is a controversy over whether cleaning the MAF actually works. I'm in the "it doesn't work" camp because I've done it twice and had bad results.

Of course I am in a Disco II but the principles are the same.

 

Hmmm.... I'll be checking out the things mentioned. I do know that the battery and alt. are good as well as the tire pressure. Sadly, I do not know of anybody who has a d1 in my area that would let me borrow their MAF. Just out of curiosity, will an earlier d1 MAF fit a later model d1 or do they have different connectors and stuff? Another thing to mention is today when driving on the highway, the truck started hesitating for a couple of seconds really bad. Then it was fine the rest of the trip. After that incident, I noticed the short term fuel trims had increased a little bit.

 

Mine has been doing the same thing, but only once every few months and then it stopped entirely for over six months. I hoped it was one of those things that had fixed itself. However, I finally was able to catch the hesitation properly on the ultra gauge when the hesitation came back for a few seconds a couple days ago, and when it happened my speed-reading was up at 87 mph, and I was going about 65. No change in the speedo needle however, interestingly enough. Must be some filtering going on there. Keep an eye on your VSS