Problems using litter box...

Hello....I am new to this site & hope I am posting properly. I think I had posted this question already but had used the wrong forum so am re-posting it.

I have a problem with my 7 year old cat --he is a neutered male & seems to have a problem using the litter box. We inherited him from my sister when he was 3-- she moved away. Everything was fine with using the litter box . She came home for a visit 7 months later for 3 weeks & then she left. Ever since then, he will urinate in the litter box but refuses to do his pooh there!! He will always do it on the floor ( which happens to be cement--thank God!! ) I have tried picking it up & putting it in the litter box so he will know that that is where he should be doing it, sometimes I cover it with litter --sometimes not.... Have even tried spraying diluted lavender oil on the spots where he goes. Have also tried completely washing down the floor (cement) with Lysol!! Also, I am using the clumping litter in 2 separate litter boxes. Could someone please give me some advice on how to stop him from doing this?? The female who is 8 years old is a sweet little thing who knows how to use the litter box. Any ideas would be greatly appreciated...:confused:

So he's been doing this for 4 years?

Have you ever had him tested for parasites or any other medical problem that might cause this? You need to do that first.

If he checks out okay at the vet, come back and we'll have some suggestions for you!