If you're going to use a primer I don't think you would have to do more than dust the walls really well. You could always ask a professional painter or call a paint store or hardware store to be sure. If the house has gas heat, the discoloration could be from that or it could be from sun light. You might try washing around that area to see if anything will wash off. I will say I'm a smoker and never had a problem, especially when using a primer/sealer. Plus if it was from a smoker I would think you could smell something, that's why I'm thinking it may be from the heating system.

I hate to admit that I'm a smoker, but since I've seen the results on my walls I think I can advise you. If the wallpaper had a vinyl coating, it probably protected somewhat by the wallpaper.

To be on the safe side, I would use a primer like Kilz. One trick I have learned is to run a warm mist vaporizor in a room. If you see the residue starting to bead or run, then some washing with TPS before priming will help. Just regular primer won't do. It has to be a sealer since the residue will come through primer and latex paint.

Menthol cigarettes leave much less odor than non-menthol. My friends are often suprised that my house doesn't smell. My car will if it is closed up, but even then, the odor doesn't linger if I'm keeping the ashtray emptied. Menthol doesn't leave less residue, though, so it can catch people by suprise when it starts coming down the walls.

Gloria

I had a problem in a house that had smokers and a small electric dryer ventd to the outside through an open window. Not an efficient process. The room was covered in little brown spots - not mold but nicotine - and did it stink! We didn't wash the walls. We painted with Kilz as a sealer, and then used a good quality paint. We've painted several times since, and have never seen another brown spot, and it's been 20 years.
Elsie

Kilz works wonders. We own a bar (that allows smoking) and always just Kilz over the walls when we paint. No smell, no bleed through, no mess.

When we bought our house, the smoker who lived there had recently painted the bathroom pink. There was a brownish patch on the wall over the toilet,right next to the shower. Every time we showered, the steam formed and rivulets ran down the wall, leaving vertical brown lines on that wall. We washed with TSP, then primed and applied wallpaper to cover up. I hate cigarettes!

We moved into a house where the original owner smoked cigars in the house for 50 years! It was terrible! We had a decorator come over for a consultation and she had to leave it smelled so bad. We used KILZ on the entire house and then repainted, pulled up carpet, etc. We still get whiffs that we suspect come from the chimney - couldn't spray Kilz there.

Dumb question...what is TSP? Sounds like something I should know about!

tri-sodium-phosphate. Very toxic. You need to follow directions carefully or it will take the paint right off. It will remove finishes from floors and any wood so it's not a good all around cleaner, but it has it's purpose.

I'm not saying this because I'm a smoker, but give me smoke over pet smells anyday. The smell of urine has cost us major bucks in redoing houses. Just a washing with TSP or sealing with Kilz can't cut that smell. We've had to replace subflooring several times in our rentals. Ugh!

Gloria