The check engine light came on in my Suzuki XL7 (2007) about 2 wks ago. Off and on as I am driving, an error will come up & say to tighten gas lid (I bought a new gas cap fr Autozone w a lock on it & have checked it several times & it's not loose?) When they hooked their machine to it, it said EVAC leak (large) and they checked the hoses & said they were fine. Any ideas what it might be? On top of that I have a constant rattling sound..when I start up the car it seems kinda rough & briefly jumpy (idk how to describe this), also when I make turns there is a knocking sound. I have an appointment to take it in to Suzuki tommorow, but I wanted to be able to be a little specific with them if at all possible...help!

I had a similar problem with a 2008 model. It was the wiring directly under the gas tank under the vehicle. It was causing multiple lights to come on at different times. Had it not been for my looking myself we would not have found it. The dealer repaired it by wrapping it in electrical tape!! That lasted a few days. They re-did it and it lasted a few months. Now it has happened again. The first dealer said "animals" must have chewed the wires. I contacted a different suzuki service dealer this time, only giving them the basics of the problem, only to have him tell me that they have problems with "animals" chewing the wires on these vehicles--almost as if he had been coached. Be very careful. The wire that control the fuel guage is in the bundle. If it breaks the vehicle will not start.

If there are no leaks between the filler cap and your tank, then the problem is somewhere between the tank and the engine. On the bright side, large EVAP leaks are easier to find than small leaks. The EVAP system stops fuel vapors from escaping the vehicle. You have a fuel vapor vent hose that runs from your tank to the front of the car to an EVAP vapor canister. From there it sends the vapors into your engine to be burned off. If you want to learn more about this you can read about it here. One of your hoses, the EVAP canister itself or maybe even your purge valve are damaged and need to be replaced. The EVAP problem is what I think is causing your rough start problems, or possibly the fuel tank pressure sensor is bad. First fix the EVAP leak and see if that solves your problem. Your knocking sound may be a CV joint going bad. Your CV boot may have been torn or just worn out, allowing dirt to get in there and grease to escape, causing your bearings to wear out. These worn bearings can creat a knock as you round corners because the joint will bind instead of performing as intended.

Hope this helps!