Vauxhall Corsa emissions light !!!!!!! help please guys

Hello guys, this is my first visit to this site and I am already looking for some help. Took my G,friends corsa out the oher week and broke the ex' camshaft in two. stripped the engine and repaired it myself, one cam+ 4 ex' valves. car now runs well but when it idles for 10-15 secs' the emissions light comes on and the power is reduced, more like a misfire, switch off and re-start and all is well, have disconnected battery and fault disappears until having to come to idle again. Also, when the cam broke the light came on at the same time, It turns out that the bearing carriers, no7&9, had come slack causing the cam to 'bounce' hopefully fixed this by using threadlok on bolts, thanks in advance guys for any help that keeps me from visiting the main agents