Yohan Cabaye responded nearly instantly for the hosts however and Sam Allardyce's side continued their recent resurgence by claiming a point when Christian Benteke struck with 20 minutes remaining.
Craig Shakespeare understandably had one eye on Tuesday's meeting with the La Liga side but the Leicester manager resisted the temptation to make wholesale changes to the team that suffered a narrow 1-0 defeat in the first leg in Spain.
Crystal Palace full-back Patrick van Aanholt has returned to training following an ankle injury and could be available to face Leicester.
After this result, he is still on course to save a side which looked destined for the second tier at the start of the year.
Crystal Palace are surely safe.
Their opening goal at Selhurst Park had felt trademark in its construction, which merely added to the Palace's frustration, given that there should at this stage be few secrets when it comes to Leicester's prowess at dead-ball situations.
Benteke almost put Palace ahead minutes later after his low effort was saved by Schmeichel at his near post following another Townsend cross.
"We have hard games coming up, none more so than this today and we knew it was going to be hard because they play a very good system".
"We knew it was going to be hard and sometimes we had a bit of trouble breaking them down".
Five wins out of six going into yesterday's game was impressive form.
Second-half goals from Yohan Cabaye and Christian Benteke maintained Palace's unbeaten home record stretching back to February.
Crystal Palace salvaged a point after coming back from two goals down against the champions to keep their Premier League survival bid on track.
Palace talisman Zaha found it hard to get into the game at first, with Leicester crowding him out. "The conversation will be with Wes and our medical department and we'll give him every opportunity between now and then but if he's not ready we won't take a gamble", Shakespeare said.
- The Foxes scored from their first shot in the game, while Robert Huth's goal proved to be Leicester's only shot in the first half. "Unfortunately for me, players forgot", said Allardyce.
Commenting on the centre-back's contract with Palace, Allardyce told the Liverpool Echo: "There isn't a clause because his deal was done in the Bournemouth corridor by me after we had won 2-0, and Steve (Parish) finishing the negotiation over the phone to try and secure Mama".