Really hard start, idle around 300 rpm. Works fine all of a sudden

[mjalstad]

When I went out to my truck from work last night, I started it up and it was was like barely even running. When I would put it into gear it would die. The wen I tried to start it back up, it took a lot of cranking to get it to fire up. I parked and got it to idle but it was idling really low, at like 300 rpms, when I gave it gas it ran just fine. I hooked up my predator it had no codes stored and the fuel trims were right on so it must have been getting good fuel. It started running better and I was able to get it home but everytime I would come to a stop the idle would dip down super low, at all times other than that it ran great and my fuel trims were right where they should be. I got home and parked in the driveway, popped the hood and it was idling ok, I gave the IAC a little tap with my knuckle and didn't notice anything different and then I shut the truck off. I came inside and got my garbage together, then wheeled the garbage can to the curb. Then I started my truck up so I could move it into the garage and it was running great, had no problems. I put my leveling keys in the front before I went to work and had the radio on for about 3 hours, then drove it to work and had no problems. Only when I left work 8 hours later did this come about. Could this be a junked up IAC or have something to do with a discharged battery since I had the radio on for 3 hours?

[jlsparky7]

I would think throttle position sensor.

[k.daddy1]

I'm assuming this is on a 99 or newer chevy. Looking at the motor on the right side of the plastic cover is your fuel pressure regulator. There is a vacuum line from the regulator that goes under the plastic cover. Remove the vacuum line from the regulator. If its wet with gas the fuel pressure regulator is bad. This will casue the hard starting and low idle.

[daddytech]

if you had the Radio running for 3 hours you may have run it down so low that it was trying to reset the ECM. that's the only thing that makes any sense to me. needed to charge the battery back up and once that was done reprogram all your tweaks. since they aren't the defaults it may have taken longer to reprogram them and once it was done again you are rolling smooth like you should be.

That's just my opinion though based on the symptoms you gave.