Car sputters when stopped at a red light

TSTRONG6600

MEMBER
2005 CADILLAC CTS
46,000 MILES

My car sputters when I'm stopped at a red light and feels like its going to stall, but it doesn't.

A little history: About two months ago my check engine light was on and the car felt like it was going to stall. A friend of mine who is a mechanic ran diagnostics and it said that one of the cylinders was misfiring. After a few tests, he ended up changing out all six spark plugs for me.

The car ran fine for a few weeks, but recently I started getting that "sputter" back when stopped at a light. To add to that, my check engine light came on last week along with a "check gas cap" warning. My friend ran more diagnostics and it said "large gas leak". He checked everything out and could not locate any smell, sound, or leak. My "check gas gap" warning came on again today.

Any ideas what could be causing the "sputtering" and the "check gas gap" Could the two be related?

Please help me out.

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,310 POSTS

As far as the large leak, I would check things like the filler tube to the fuel tank. Also, have your friend check to see if the same cylinders are missing. If they are, there could be internal issues within the cylinders.

Also, to locate the "large leak", you may want to have the EVAP system fogged. They actually pump fog into the system at a very low pressure. Once they do that, it will leak out where there is a problem and you will be able to locate it.