Check Engine Soon

i received a code of p0171 and 172 i had the o2 sensor repaced and the code cleared, within the same day the check engine soon light came on again giving the same codes the machanic said it was a coil pack so he replaced it and a day later the light comes on again, i am running out of money, sometimes in the morning when i start the car it idles down then it shuts off after the second attempt it stays on. what could be causing this problem?

If there was one bad coil pack, replace them all. Year of your Max?

~THT

2000, where should i look to find inexpensive coil packs?

Thanks