Fall Out Boy [ tickets ] bassist/lyricist Pete Wentz was miserable. He and the rest of his pop band were set to play the Phoenix area's Peoria Sports Center as part of the Vans Warped Tour. But there was an uncomfortable problem--it was 100-plus degrees outside, and the air conditioner on the band's bus was broken.

"Is anyone else hot? I'm really sorry about this," said an overly apologetic Wentz. "I can't even think."

The complaint is the first of two times the soft-spoken Wentz raises his voice. Shyly, he corrects a reporter's comment that Fall Out Boy's latest album "From Under the Cork Tree" debuted at No. 16 on The Billboard 200. In fact, he said, it entered the album chart at No. 9.

"Not to split hairs … It's definitely a surprise," Wentz said, his voice rising. "I think it's just that our fans have always been cult-like and [use] word of mouth. We achieved all that without radio and MTV."

Fast forward: Fall Out Boy tops MTV's "Total Request Live" chart with the cheeky video for "Sugar, We're Goin' Down."

While awaiting their sweaty set at the recent Warped Tour stop, Wentz and vocalist/guitarist Patrick Stump sat on their equally sweaty bus and talked to the media.

Last year you played the Warped Tour on one of the smaller stages. This year, you're on the main stage. How has this Warped Tour differed from the last?

Pete Wentz: Honestly, it's not really that different. Last year we were playing on smaller stages, but the ratio of the crowd is very similar.

Why do you think people keep coming out to the Warped Tour when it's so hot?

PW: It's crazy seeing kids passed out. I think people think it's part of the experience, a little bit. It's the same thing if you go to summer camp. You get mosquito bites. It's not really a reason to go, but all the other things that go along with it are cool.

What was your most memorable moment of playing the Warped Tour last year?

PW: I think the most memorable was Detroit [Pontiac Silverdome, Pontiac, MI] last year. We played on a stage for about 400 or 500 kids but 4,000 or 5,000 kids showed up. During our second song, the barricade collapsed and the stage tried to collapse because there were so many kids. They pulled the plug and we only played two songs that day. Some of the kids sang one of our songs by themselves. It was cool.

Warped is 11 years old. Had either one of you been to Warped before you were scheduled to play it?

PW: I saw New Found Glory and Green Day on Warped before.

How did you all meet?

Patrick Stump: The band just kind of happened through all [of us] hanging out in the hardcore scene. I randomly bumped into Joe [Trohman], our guitar player, who often said I could sing. I didn't know whether or not I could. Basically, we would have been a hardcore band, but I was just singing, so we made our own band around that. We didn't have a name, and someone shouted it out at a show.

You've come from hardcore bands. What do you think you have brought to Fall Out Boy from those bands?

PS: It's funny you say that. I was in a band years ago, and the guitar player was absolutely amazing. Half of my writing is me trying to play as good as that dude. He's just some weird a-- who doesn't do anything now. I don't even know if that dude talks anymore. He's just crazy.

What is the songwriting process like with Fall Out Boy?

PW: I write words all the time and give them to [Stump] when he's writing music. He's writing music all the time, too.

PS: It's like, we're not in bands because we want the MTV. We're in bands because we enjoy doing it. Whenever I'm not doing interviews, I'm probably writing music and he's writing words, and at any given moment we're putting something together.

Have you started writing a new album yet?

PS: We haven't really started writing an album. But we're always writing songs. We're not planning it out yet. We just got off that last one.

What was it like to record with producer Neal Avron?

PW: We recorded in Burbank. It was cool. A good experience.

PS: He was great. It was weird because this was our first-sit-down-and-make-an-album album. He kind of helped us out doing that. It was good to have him. We had been writing in some form or another since the last one ["Take This To Your Grave"]. We had a lot of songs to work with and, ultimately, we got to pick the better ones rather than having to scramble to write 12 songs.

How does "From Under the Cork Tree" differ from your last album?

PW: The content's a lot different. It's not more mature. But whenever we take the crystal ball out of the bowling bag in the closet, it's always cloudy. It's easier to reflect on the last record. The last record, when we wrote it, we didn't think anybody was ever going to listen to it. All of a sudden, there are people who knew every single word on it. We knew that going into this record. So there's a lot of references to just the idea that the whole idea that everything you say is under a magnifying glass. Those are the primary differences in the content.

PS: I think, lyrically, it was more focused this time around. The music had more backbone to it to accommodate that. I love our last record. But with this one, I think, Peter gave me better stuff, and so I had to rise to the occasion and write better stuff. I had to write something that felt like it made sense underneath what he was saying. It's a little broader. It's heavier, it's more melodic. Every band thinks they're doing something way better than they're actually doing, and way greater than they're actually doing. I think we just made the music that needed to be made around his words.

Do you find inspiration in other bands?

PS: I don't think we're consciously ever trying to put too much in that anyone would notice. I mean, yeah, we like The Cure, Descendants, Elvis Costello.

How do you feel about reaching the top of "TRL"?

PWz: I don't know. It's so funny. We're on there with Mariah Carey and Kelly Clarkson.

PS: How bummed has Mariah Carey got to be?

PW: I think she probably doesn't even know who Fall Out Boy is. I think it's kind of surprising that there's this groundswell of fans. Kids are excited to see us on "TRL" because they don't really know what's going to happen when we get on there. We're liable to break all our equipment.