Thread: Hey everybody. Got some problems

First off hey everybody. I'm Shane, the new owner of a 2000 Grand Prix GTP, so here I am. I found this place doing research before I bought the car and it looked like a great community so I figured I would make an account now that I own it.
My car is a jet black coupe with quite a few aftermarket mods put on by the previous owner. It's very clean and it ran great when I picked it up. However now about 2 months later I'm having some pretty serious looking problems, which I gotta say is really why I'm here. I paid $3850 cash for this baby and I need some expert help to fix it, lol. This is actually my first car I've ever owned, and I really have no experience working on cars, but I don't have the money to make all kinds of shop repairs so it sounds like I need to learn quick.
The issues I'm having started the other day, I went to start my car and it turned completely on for a second, then kicked back off as if I turned the key to on. It still had electrical but maybe no fuel? That happened a couple times then I waited a few minutes and it started, but ran funny after that. I had enough power at like 10% throttle before but now I have to give it a lot of gas to even drive at normal speed, especially uphill. The stalling on start issue has continued occasionally. The steering also got noticeably loose, my car is lowered so it handled very tight before but now it has some play. a CEL also appeared which I scanned at advance and the guy told me it was a P0440, which apparently means a large evap system leak or no vacuum. Since I've bought it and had to replace the battery the computer went from reading 24 mpg to only about 14 and then down to like 12-13 lately (no highway driving). but that has to be some kind of problem anyway, I'm driving a sports car not a hummer. It's still driving ok except for those issues, and a good mechanic i know took it for a ride and said it was safe, but there was some restriction somewhere and my best bet is to take it to his shop. On top of all that I also have an HID light out but I don't think its the bulb, maybe the ballast. If anyone can offer some help it'd be greatly appreciated, otherwise I'm gonna owe an arm and a leg. :/

Mods/Upgrades
-full TOGs headers
-flowmaster exhaust, cat removed
-aftermarket GTP valve cover
-sparko racing plug wires
-modular SC pulley system with 3.4"
-aeroforce scan gauge (no longer working) and boost gauge
-1" lowering springs
-drilled and slotted rotors
-K&N cold air intake
-HID headlights, high beams replaced
-I believe throttlebody is also aftermarket
-180 degree thermostat
-JL 250 watt amp and 12" sub
-interior speakers also replaced with Momos
-18" chrome pontiac wheels, not sure what year/model
There may even be more I don't know about/forgot, I have oodles of stock parts

I'd scan the O2 sensor. Fuel mileage like that is often a dying front O2. Also on the evap leak...with the mods you have, I'd want to see if that appears to be modded at all. If not.. check your gas cap, evap soleniod (for a vacuum line break) and the evap canister that is located behind your driverside rear tire.

Kinda funny, I looked the code up for another local guy last night.

Being local, if this stuff continues...maybe we should hang out and see about figuring these things out. On the Aeroforce, check the power and fuse going to it. (at fuse box is the most likely place for an issue)

welcome to the site

What you're describing with rpm and exhaust. That's just the colder weather here lately. Perfectly normal when you first start the car for the idle to ride. Thank your iac valve.
Humming noise? Details? Engines hum

See, perfectly normal!

No pooling anywhere I could see, I took it to the shop and he said my car is stalling due to the anti theft, and he also said to replace my gas cap first off because it has a crack. So I guess we'll see if it runs any better with a new one

Edit: so with a new gas cap im getting about 1mpg better driving around but no change to the actual problem, I kinda figured that was a giant waste of a trip. Basically he just told me my car was modified. I was thinkin yea no **** lol...

But another detail I noticed: when I turn the wheel in park, the idle goes down by like 200 rpms, especially to the left. That doesn't seem normal