After driving for about an hour...then if you go up a hill or steep grade it acts like it is going to die. As long as you are on level ground it is fine..only happens driving up hill. The car will go from do 60mph to barely doing 20mph and leap frogging.

check and test belt -stretched or worn --

No
not if you drive it accordingly
steep hills are best negotiated in low fears with plenty of rpm applied
for example on a steep grade with a manual 1st or 2nd or possibly 3rd and the rpm around 2000 constant will cause it no harm
automatics will go to first automatically so keep the rpm at that mark
engine damage is experienced when the gear selected is too high and the engine is placed under extreme load so down shift to allow the engine to work easily
When going down hill select first and only use the brakes to maintain the 2000 rpm range and allow the engine compression to hold the car speed back
the rule of thumb for experienced drivers is this
you select the same gear to go down that it took to come up

An automatic will not roll back on a gentle hill, but could do so on a steep hill. God-Bless! The torque convertor can only hold back if the grade is not to steep.

Surges under load but only while going uphill Page1 - Chevy High ...

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Mar 6, 2011 - 14 posts - ‎8 authors
Trying to help out a friend. ... The truck starts, runs, and drives fine until you get to a hill. When going up hill it begins to surge, almost stalling but not quite. ... rubber fuel lines suck shut under a heavy load and act like that. .... tranny fluid level o.k.? ya got me stumped. runs great when it's on a flat surface?

Ford 460 engine - RV mechanic

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Will not take gas going up a hill but will maintain speed at 55 mph. ... Want to do a diagnostic test on my 1997 F250 with 460 engine. ... only get to about 40 miles an hour if i push it the engine acts like its running out of gas,thank you .... The truck hesitates on acceleration, while driving on flat surface is fine, however climbing ...

rough idle, stalling, loss of power. - CarGurus

It will lack lots of power going up hill, especially if its a really steep one and you keep it in drive. Make sure you downshift to second, or fist if its really steep.

What you may be hearing is called "octane ping". It occurs when the engine is under heavy load and the fuel does not have enough octane to efficiently run the engine. Older engines like yours were often run on premium gasoline to avoid this. However, if you do not have the clacking when accelerating on level ground and only have it on the steeper hills, it is not necessary to spend more money for mid-grade of premium fuel. Only if the engine makes the noise under normal operation is this advised. A little octane ping in those situations will not hurt the engine. But, if you need the peace of mind, and to ensure that the clacking IS octane related, I would try one tank of premium and retest the engine of a hill you know causes the problem to see if it goes away.

have trans shop check operation while during test drive

1/4 tank on the flat. You fuel system is sucking air on a grade bcause it is all going t the front of the tank. !/2 tank is about as low as you should go.

two things that i would check first, make sure parking brake is off, then check trans fluid level (engine running, in park, on level ground) also do you park the vehical on level ground at night? my car acted like that the other day, my driveway is at a steep angle, parking it nose up hill, when backing out, it coasted back no problem but when i hit the gas to back up a little more, i got nothing. waited a few seconds then it grabbed. then i backed up with no problem.

It may be a leaky injector. The injector is connected to the bank. 1 of 2 fuel rails.