Suddenly sputtering at acceleration

**Dontcounttoday** · 02-03-2017

My '04 Grand Prix with 130k miles has a few issues that may or may not be related, so I will list what seem to maybe be connected.

The vehicle has for as long as I can remember have difficulty starting on a hot start without giving it gas while starting the car. About a month ago my Check Gas Cap earning came on, followed soon after by an engine light. Neither has gone away by changing the gas cap with a new one. About the same time the hot start issue has gotten much worse, with the car dying when turning the ignition unless I give it quite a lot of gas. On top of those, and about the same time as well, I'm getting a weird issue where I cannot fill up my gas tank fully. The pump cuts off like it is full after just a gallon or two make it in. Sometimes I have to keep waiting a few seconds then pumping more and it cuts off again. Sometimes I can just let the gas flow slowly until full. Almost like the gas isn't get into the tank fast enough and backing up. Not sure what that's about.

Now, in the past couple of days I am getting sputtering while accelerating. I planned to take it in for a tune-up which is certainly overdue, but if this may be more clearly connected to the gas cap and hot start issue, I'd love to hear any ideas.

**Keko** · 02-03-2017

To me it sounds like two different issues.

Difficulty starting when already hot seems like a dying MAF. I had the same problem. It started great when cold, but after being off for more than 2-3 minutes, i would have to give it gas to keep it running for the first 5 seconds or so, it sounded like a lawnmower. MAF was reading airflow wrong and dumping tons of fuel. To confirm it's your MAF, get the car hot then unplug the MAF. It should start on it's own with the MAF unplugged. It might struggle a bit, but it should be a lot better than what you are used to.

But above all else, you should really see what codes you are throwing... any reason why you haven't done that?

**Fivefingerdeathpunch** · 02-03-2017

Clean the throttle body for the starting problems, I bet it's just caked with black crap from the EGR and causing you problems. It's a very very common issue.

The gas filling up problem sounds like the vent for the gas tank is no longer working, it is not allowing fuel vapor and air out of the tank when you pump fuel inside. The actual code number the check engine light gas will tell you what might be the problem.

Past that I'd do spark plugs and wires, clean the MAF sensor and see how it runs afterwards.