When in sleep mode iPhone 4 loses signal but when it s back on it searches and finds signal. Was 5.0.1. update to 5.1 but no changes

it could be a motherboard problem. Last month I spilled liquid on to my iphone and since I didn't have warranty for it I had to take it to a "phone doctor". He fixed it but mentioned that motherboard is working fine but he can not say for sure for how long it will last, and that I may experience some wierd problems. I'm having this exact problem the day I got my iphone back.

Well no longer but the solution still seems wierd. I turned on the "location services" because I saw in the "system services" screen that "cell network search" was turned on. I figured if I don't screw with location services, it would be okay. So, after three hours, I terminated the sleep in 10-20-30 minutes and 1 hour intervals, it seems I no longer have the problem but I'm going to sleep over it to be sure. Also make sure to turn on the "auto" option on the "carrier" menu.

I will post the outcome if I don't forget about this page.

it could be a motherboard problem. Last month I spilled liquid on to my iphone and since I didn't have warranty for it I had to take it to a "phone doctor". He fixed it but mentioned that motherboard is working fine but he can not say for sure for how long it will last, and that I may experience some wierd problems. I'm having this exact problem the day I got my iphone back.

Well no longer but the solution still seems wierd. I turned on the "location services" because I saw in the "system services" screen that "cell network search" was turned on. I figured if I don't screw with location services, it would be okay. So, after three hours, I terminated the sleep in 10-20-30 minutes and 1 hour intervals, it seems I no longer have the problem but I'm going to sleep over it to be sure. Also make sure to turn on the "auto" option on the "carrier" menu.

I will post the outcome if I don't forget about this page.