Hard to get started

Hello. I've got an '01 accent and recently I've been having a hard time getting it started. It takes about 3 times of separate attempts of cranking to get it to start and remain running. It usually won't even respond to the throttle even if I floor it right after starting. Once it does catch it sounds like it is rattling real bad and sometimes the check engine light flashes. Once it goes through this routine it runs perfectly ok. This typically only happens when the car has sat for a while. I've had a check engine light on for a long time and never bothered to pull the codes. Does anyone have any idea as to what the problem may be?

Sounds like the fuel pressure regulator could be bleeding back. Get the codes checked though and see what they say.

Ok I finally got the codes pulled. It is giving P0141 and P0136 downstream O2 sensor faults and also several cylinder missfire faults P0304 P0303 P0300. I changed the plugs and wires within the last 5,000 miles so that somewhat elminates some of the probable causes for the missfires. It is missfiring on start up but then that seems to go away. I'm going to check the plugs tomorrrow and probablly change the wires just in case. I'm thinking the 02 sensor fault is likely the result of the hard starting tendancy. It definately is running rich at least on start up due the fact that the tail pipe is black and it emits smoke on the first start up of the day. I have to put the acclerator to the floor to get it started then it backfires and idles really rough for a bit then it idles normally. I've also noticed that the engine rpms intermittently take a couple of seconds to go back to a normal idle (stays at a high rpm)

Any thoughts or suggestions would be greatly appreciated.

Its a serious problem and you should get solved for it immediately, because it can cause lots of problem for you. Better go to the service center for this.

Sorry I forgot to follow up on this. It turned out to be the mass airflow sensor. I disconnected it and it immediately ran a lot better. I replaced it and the O2 sensor and she's running great. Also went ahead and threw new plugs and wires on it just to be on the safe side.