Hello,
I drive a 1990 Isuzu Impulse, manual transmission. It drives pretty well overall. I’ve recently noticed that it looses power dramatically on hills though.
I got advice that it might be an old fuel filer or a failing fuel pump and would like some feedback if anyone cares to chime in.
I replaced the fuel pump, which offered a little relief, but the problem persists. I am now thinking about the fuel pump.
on a highway for instance the car will cruise along nicely say at 60MPH, once I hit a hill though, the car will steadily lose power until it crawls to, amybe, 45MPH and I am forced to downshift to pick up enough power to make it over.
My current theory is that my (electric) fuel pump is gradually loosing power and is unable to get up enough pressure to supply the engine with fuel. But hey, if I new I wouldn’t be asking you geniuses huh?
So if anybody has any thoughts, i.e. “That is a bad theory, you need to get back to the drawing board”, I’d certainly appreciate it. If the mob says fuel filter, I’ll go ahead and drop the $250.00 for the part (ouch!). Thanks so much for any ideas.
peas (and carrots)
promet
OOPS! I said in the post that I replaced the fuel pump, typo! I replaced the FUEL FILTER. heh…
Man, I cannot type, it’s supposed to say, "If the mob says ‘Fuel Pump’ ". I’m really not this stupid, I swear, maybe 3/4 this stupid, tops. 
The mob can’t see your car… you should get the fuel pressure tested before you plunk down the big bucks for the fuel pump. You will go broke fast replacing parts you don’t know are bad.
If it hasn’t been done in a while, change the plugs, cap & rotor (maintenance items) and check the timing. Low engine compression is also a strong possibility, so a compression test should also be in order.
When you are going up hill you are using more power, requiring more fuel, and the pump has to pump it up hill. A weak fuel pump will do exactly what you are describing. However What you describe is not much different than the description for a clogged converter.
What happens if you try to acierate briskly when driving at say 60 mph? If you get the same problem, my guess is a failing converter. If you don’t have a problem, then I vote for a weak fuel pump.
just curious.
like greasy jack asked, when was the last time the plugs, wires and cap rotor replaced?
also, are you driving new places, steep hills? got a load on the roof (roof rack, or cargo bin up there?)
these thing do affect the cars up hill performance.
i ask because i have a 2000 mazda truck and i have to down shift going up steep upgrades (always have since new) what has changed in where you are going since this started?
The cap, rotors, plugs and wires have all been recently replaced (like 5 months ago, which pretty good quality parts). Accelerating briskly from 60 MPH has always been very slow; i.e. it’s pretty brisk getting up to 60 MPH, but beyond that, acceleration is pretty sluggish.
At the point I noticed this I was, come to think of it, carrying quite a bit of cargo in the car with me. Also, I was traveling cross country at the time is well. So, yes, a lot of new roads for this car. Thanks very much for your replies by the way!