PO304 misfire presents when going up prolonged hills, any ideas?

Question

1999 Chevy suburban, 130k miles. 5.7. New exhaust, new plugs, rotor, wire and cap within 6000 miles. Problem showed up on my way to Maine. Service engine light did not come on until the third incident. It does fine on level roads. Has a slight hesitation when accelerating, but nothing major. Main issue occurs when I go up long inclines it hills. About half way up, there is a definite problem. With consistent pressure on the gas , the entire engine begins to shake, no loss of RPM and normal 4-5 MPH drop in speed. It feels like a misfire. Code PO304

Answer 1

You definitely do have a misfire condition, , these distributor caps are popular code for misfire on either cylinder 4 or cylinder 7, just by its design what happens inside the  distributor cap 4 and 7 tends to short out internally causing the misfire condition, Because this is a recent misfire condition, get the distributor cap replaced.