how to fix bad tuner?

I just recently installed a pioneer avh-p4000dvd in a 2008 kia optima. Everything works great, except for the radio. While I am driving it, the radio fades in and out excessively. I pulled out the radio and checked the connections and they are all solid. The radio worked fine on the stock stereo, so after talking with the tech support from pioneer electronics, I figured it was a faulty tuner inside the unit. Is there anyway to fix this problem without having to return the unit to be repaired? I bought it online, and it seems like it will be more trouble to try and have them fix the problem, so I am looking for other options first. What about fm boosters, or HD tuners? I know I don't need radio with all the other functions on this stereo, but I do like to listen to it from time to time. Thanks

Does the Kia have a power antenna that is no longer being powered?Kevin Pierson

That was my guess... My Civic was the very same thing, until I doscovered the antenna amplifier in the passenger's C-pillar. The stereo may or may not have a power antenna lead on it. If it is there, it needs to be connected to the power antenna lead in the factory harness. During installation, you may have not connected it, thinking "I don't have a power antenna". If it is NOT there, the car's power antenna lead needs to be connected to the acessory lead. While it does NOT make the antenna go up and down, it DOES turn the antenna amplifier on.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

I only connected the blue/white wire from the pioneer stereo to the blue/white wire of the kia harness. It did have a blue wire, but because I didn't see any visible antenna, I didn't connect it.

Even more the reason to connect it.  Hidden antenna, means it probably needs an amplifier.  Connect the Blue wire to the Blue wire on the new deck. 

Check in the car's radio harness for a grey wire. If you can plug in the original radio and test this wire for 12 volts when you turn the factory radio on/off. I believe this is the antenna module turn on circuit. Most vehicles that use a windshield antenna have a module attached to them. This module must be turned on/powered to work. Use the Blue wire from the Pioneer to activate the circuit if it is there.sparky

There is no blue wire on the pioneer harness. So do I hook it up along with the the blue/white wire or the red accessory wire. Or should I just not connect the blue/white wire from the harness? I don't know if the car has a factory amplifier, but I connected it just to be safe.

I have no idea of the current consumption of the Antenna Amplifier.  Just to be safe I would connect it to the accessory wire of the radio. 

I hooked it up to the accessory wire, and the radio is working great. Thank you all very much. You saved me from spending unnecessary money on this project.