Injuries struck Newcastle in the opening stages, and Eddie Howe was eventually forced to replace top scorer Alexander Isak with Harvey Barnes at the half’s midway point.
The frequent stoppages disrupted the flow of play throughout the first half, with neither able to muster a single attempt on goal until the half-hour mark when Trevoh Chalobah’s ambitious effort sailed harmlessly over Nick Pope’s crossbar.
Palace gradually emerged as the more likely side to strike in a cagey first half, and the Eagles nearly opened the scoring for a fourth time in five games when Ismaïla Sarr’s whipped cross was poked wide by Muñoz from six yards.
Maxence Lacroix also went close, rising to meet Eberechi Eze’s free-kick, but the Frenchman’s mistimed header went wide to leave Palace goalless for a sixth first half in seven home matches this season.
The contest was there for the taking after a drab half that saw neither outfit register a shot on target. But it was the visitors who emerged the better, as Howe’s HT team talk inspired Newcastle to score shortly after the restart with Anthony Gordon whipping a low cross into the Palace box that Marc Guéhi inadvertently flicked into his own net.
A Premier League opener is usually a good omen for the Magpies, who have won all three prior matches when striking first this season, and the visitors held firm against Palace’s initial response as Dan Burn slid in to block Muñoz’s goal-bound shot.
Just as it looked like Howe’s men would comfortably hold onto their lead, they were undone by a late lapse in concentration as Muñoz atoned for his miss in the first half by levelling the contest in the fourth minute of stoppage time.
His downward header eventually bounced over Pope on its way in to score for the first time in the Premier League and rescue a potentially priceless point for his side, who have now lost just once in six matches. Newcastle, meanwhile, missed out on the chance to climb into the top-seven as they failed to win on the road for the fourth time in five attempts.