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Bucking Chevy

"89 Caprice 305(116,000 miles)has no power on hills, or acceleration. No “Service Engine” light is on. Car tends to buck and backfire when giving gas or trying to go up a hill. (lightly pressing gas pedal will allow forward motion and increase in speed, eventually)

Changed plugs and injectors, no help. The injector spray seems to be normal and conic.

Any ideas??

Did you check the fuel pressure? Fuel pressure regulator? Give it a new fuel filter?

I’d also slap a vacuum gauge on it to check for exhaust blockage.

First, does the check engine light come on before you start the car? If not, you may want to have the codes checked. Bulbs do burn out and shady used car dealers have been known to remove check engine light bulbs.

If it does work, try some new plug wires

Worn timing chain? Timing off? Worn out camshaft? Measure how high the rocker arms lift, when turning the engine by hand.

Thanks all, for the responses:
Fuel filter has only 10K on it but I am suspecting fuel pump and will perform the pressure test. (I have a pressure regulator gasket/assembly from the injectors’ package I bought but my shop manual cautions against taking the screws out of the regulator due to the compressed spring; but other than the spring and this gasket assembly I don’t know what could go wrong with the regulator) Also a test for blocked converter probably is in order. Don’t think timing chain is involved because engine starts up immediately. Check engine bulb is OK ( I suspected burned bulb also and checked for that right off).
Its probably going to be the fuel pump in the tank and, after having replaced one of these “on the ground” – no lift, am not looking forward to doing it again in this Missouri spring/mud. So I will give the business to my local guy with a lift and a warm shop.
Thanks again for the help – no one mentioned electrical problems which I thought might be a posssibility, but maybe not.