Why does 97 camry looses engine power when driving up hill

Most likely a faulty EGR valve. It does cause these problems to happen.

if it is doing it consistently take them out for a test drive up a hill.

how is the engine oil ? when was it last changed as old oil is less effective , try an oil and filter change , but a hard rattle as you describe it may be something ,not more serious , but maybe a loose drive belt or some thing that when engine revs increase's it becomes noticable though is still there ,if oil change makes no difference have a good listen around engine also underneath to try to narrow down location , hope this helps keep me posted if you wish

this makes no sense.
sorry.
please post symptoms fully, (good and bad) on 96 camry

you run compression tests driving?, would make the best video on earth, let the monkey sit on engine, hood missing
and you driving.
is this an engine issues.
or transmission?
or what/

flashing is usually a sign of a bad misfire situation, check the plugs and wires, also check for coolant in the oil or oil in the coolant.

I do think that loose key and keyway could cause the knock. It would also explain the loss of power, due to the engine timing not being spot on.
A knocking big end or main bearing would not improve at higher revs, it would get worse.

Act soon before the keyway in the crankshaft itself is too badly damaged, by removing the crankshaft pulley, lower timing belt cover, and belt guide. You can then get a precise idea of what exactly is worn. This may assist

http://www.turboninjas.com/camry/eg1.pdf

You may actually have to find an oversize key, for a neat fit in the crankshaft. It may be necessary to file or grind it to fit. Engineering supply houses stock them, eg

http://engtooling.com/webshop2/

It looks like it may be the transmission. Is it only in drive?

could be alot of thing kia's a/c draind alot of horse power ,plus going up hill.try turn of a/c on hills.thats the owner of 3 kia's opinion . engine lacks power obstructed exhaust ,catylitic converter. defective plugs and or wires. fuel injection needs cleaned , air filter ,automatic transaxle fluid to much or to little and last my favorite the emmision control system . these are just the main culprits . only you can be the judge of how steep the hills are and how bad the power loss is

I would suggest an automatic transmission flush before I did anything else.

there are two conditions
1)
pls clean up ur vehicle's HEAD (which mean the spare part immediate attachment to the engine and keep the Nozzle pressure is high )
2)
Get rebour ur engine I mean replace the piston rings

3) (this is for temporerly)
before the hill u stop ur vehicle for some time (say 15 mts) so that ur engine is get cooled after that u have ur driving