So I have a 98 Discovery with about 135k miles on it. Fuel pump went so I replaced it with another. Will give you the brand and napa auto part number if it helps diagnosis. Everything was going fine. Drove a day or two. Now I have this pulling feeling everytime i press the accelerate hard, if I just lightly press on the pedal it's fine but if I press hard even the slightest bit the truck pulls like crazy and sounds like its running out of gas or something like that. I have no idea what the problem is. I mention the fuel pump b/c that is the last thing I took care of. I'm not sure if its the problem or not. I am going to replace the fuel pump, I just want to get a good one this time so any ideas on which brand is the best and quiet would be good, but I really need to know what's wrong with my truck. Its my only mode of transportation. Let me know if you guys need anything else to go in. thanks

 

Do you have any way of checking the fuel pressure ? and did you replace the fuel filter ?, a clogged or partially clogged fuel filter wil put a serious strain on the pump, as well as cause driveability problems. I believe that with the truck running you should have ~ 32-36psi at the fuel rail check port. Definitely change the filter though , if you haven't already

 

Ditto.
Also are you throwing any codes?

 

I've had the same thing going on with me as well. 98 disco I with 138000 miles. I replaced the fuel filter last week. I wouldn't know if it's the fuel pump going bad?
sorry to hijack your thread.

98 disc I
138000 miles

 

fyi..............I just bought a fuel pressure test kit @ harbor freight...it was on sale for $9.99
it may not be the highest quality piece out there, but it should do the job for occassional use.

 

It could be your VSS (vehicle speed sensor) going south.
But we need more info first, when was the last time you had a tune up?
You can buy the fuel filter at Wal-Mart for $15.
It is supposed to be changed every 30,000 miles.

 

Alright so I changed the fuel filter around 2 months ago. I just bought a pressure tester, so I'll check that when I get back to my truck I had to rent a car to head cross state, where I am now. As for a tune up - I've never bought a tune-up or taken it into lr dealer, I've done it all myself; plugs, wires, starter, alt, batt, air filt, fuel filt, fuel pump and a bunch of little cosmetic things (fuses, door lock springs, ...) That's all I really know I had problems with or knew needed changing. Anything else I would gladly tackle - I'm horrible at diagnosing the problems, so I search all the time and find the easiest thing to the hardest. and tackle accordingly.
So I'll check the pressure - but I did think that at first so I pressed in the fuel pressure valve when the car was off and nothing came out. But as I read the instructions for the pressure reader it says the vehicle needs to be on, either way just seeing if that points to anything. thanks.

 

I wish the tester I bought was 9.99, it was 43 at advance auto, none of the other 5 stores I visited had one.

 

Mine has the same issue. Has for 2 years now. When I brought it home it had the normal cyl misfire codes the o2 code (downstream something) and the one random misfire code. Did as instructed: seafoam induction, TB cleaning, oil change, new +4 plugs, magnecor wires, fuel filter and pressure washed engine bay (for fun) and even got 4 new O2 sensors (for the downstream code).

Nothing. Truck still bucks, spudders, and acts a fool.

Went on to replace the next possibles: VSS and the Coil Packs.

Nothing. Truck still bucks, spudders, and acts a fool.

I've replaced literally everything related to 'misfires' 'hesitation' 'backfire' 'sluggish' and whatever else with absolutely no luck. Still have the misfire codes. At this point I've learned to deal with it. I drive with a heavy foot and shift manually (auto trans). This is the only way I've found to avoid the annoying hiccups.

Hope you get yours figured out! I just gave up.

 

Really bad engine sludge and carboned up valves can both cause this really bad hesitation that cont be "fixed".
This is caused by using the wrong grade of gasoline.