I turn my car on and the rpm jumps to 2000 and then fluctuates between 1500 and 1000 all while stuttering. The weird thing is that when the a/c is on the car runs fine and when its off it stutters and tries to stall. When its in the drive gear and I have my foot on the break at a stop sign or red light it starts to stutter and tries to stall so I add a little gas so it won't. I took it to get diagnosed and came back with codes P0171 and P0300. Took it to a mechanic, he said he couldn't figure out what was wrong but he cleaned my TB, MAF, and Throttle Plates, paid him a hefty fee and was upset because my car wasn't close to being fixed. It ran a little better and I just changed the MAF yesterday but the problem continues and I don't know what to do. I thought it might be the IAC valve but I couldn't locate it so I gave up and came here.
Does anyone know what the problem could possibly be?
If it is the IAC valve could you tell me where it is located please?
(I'm a girl and don't exactly speak car and driver so the more details the better).
Thank you friends!