: 2004 STS running rough and making hissing noise

05-15-12, 12:17 AM
My 2004 STS check engine light came on about a week ago. I noticed today that there was a hissing noise coming from the engine. My neighbor looked at it and said that the vacuum hose was loose. He followed a hose that was on the left side of the engine to the back and did something back there that I couldn't see. Now when I started the car, it runs rough as hell. What could this be and how much is this going to cost to repair? I'm afraid to even drive it to the mechanic to try and get it diagnosed.

05-15-12, 12:47 AM
Not sure, however you may get more help if you posted in the right section, if you have an 04 STS then you have a Seville (FWD - completely different beast), and if I recall correctly they didnt make the 04 STS in the USA at least so then you likely have an SLS.
I guess I would ask the neighbor what he did to it first.

05-15-12, 04:40 AM
While there is a section (for your Seville), this question may be generic enough that your answer can be answered here; I believe you have a vacuum leak somewhere and you'll have to try and track it down by listening for it. Good luck.

05-15-12, 11:50 PM
As a 2004, isn't it a Seville Luxury Sedan - SLS. I think the last FWD STS were 2003 models.