In an end-to-end encounter, it was Paddy McCarthy who got the better of City’s academy manager Craig Bellamy, with substitute Ajayi popping up with his first goal of the campaign at just the right time.
Palace started well with TQ Addy forcing Bluebirds goalkeeper George Ratcliffe into a good save with a strong blast with two minutes gone, but the Eagles would be indebted to their shot-stopper during the first half as their hosts piled on the pressure.
Rohan Luthra would make his first save of the afternoon when Rubin Colwill got through the defence and fiercely struck towards goal but the Eagles keeper tipped over, and on 26 minutes Palace received a let-off though when Isaak Davies pounced on a mistake at the back and teed up Colwill who fired a golden chance over.
Cardiff continued to press but again Luthra was equal to a low Davies attempt that skidded off the wet turf, and two minutes after the break City netted through Ryan Kavanagh from close-range, but the effort was chalked off for offside.
The best moment of Luthra’s day came on 56 minutes when he produced an excellent double save to once again deny the lively Davies as well as Dave Griffiths, but Palace could have netted soon after when Sean Robertson saw an attempt blocked by the legs of Ratcliffe.
However, with 10 minutes to go Palace pounced. Having only been on the pitch for five minutes, Ajayi met a Joshua Malcolm cross and sent the ball past Ratcliffe to clinch a second consecutive win for McCarthy’s side.
Palace: Luthra, Russell, Onoabhagbe, Boateng, Chamberlin-Gayle, Gurung, Robertson, Addy (Ajayi 76), Keutcha, Street (Malcolm 46), Aveiro. Subs not used: Trehy, Matthews, Donkin.