battery issue Battery Light HELP

[Dylan Schultz 0]

i have a 98 ls400 with about 244,000 miles on it. I’m having this very odd issue with the car. When I come to a stop light/ sign, the battery light comes on, rpms drop straight to 0 and the engine dies. Air and radio some times stay on. If I put it in park and restart the car the light goes away then its fine to drive until.. ya guest it I come to another stop. It does the exact same thing over an over at each complete stop. I assumed it was the alternator and I replaced it yesterday. No battery light, or weird idols happened for about a day. it is back to doing the battery light thing. If anyone has any Ideas of what it could be, or how to fix this issue id really appreciate it. ALSO not sure how old my battery is, changed the negative battery terminal when I did the alternator. Positive could be the problem (Corrosion on positive terminal) or maybe the terminal cable(s)?? Im very new to working on cars and any information is appreciated and retained. 

[sha4000 55]

You should have checked your battery first before changing out the alternator. You should have a check engine light on so pull the codes and post back here. This could be a MAF issue. Does the car die while idling in park?

[Dylan Schultz 0]

59 minutes ago, sha4000 said:

You should have checked your battery first before changing out the alternator. You should have a check engine light on so pull the codes and post back here. This could be a MAF issue. Does the car die while idling in park?

Does not die while in park, will post back when I get the codes pulled. 

[sha4000 55]

With that many miles It could be Your maf sensor, IAC valve, throttle body probably needs to be cleaned also but the codes will point you in the right direction.

[vissine 12]

I think sha4000 is right about IAC valve. I would clean it first.

[Dylan Schultz 0]

19 hours ago, sha4000 said:

With that many miles It could Your maf sensor, IAC valve, throttle body probably needs to be cleaned also but the codes will point you in the right direction.

Pulled the codes, only code is for my transmission solenoid C needs to be changed. No other codes. 

[sha4000 55]

This is for the shift solenoid C.

You can try cleaning your throttle body First but make sure you don't have any vacuum leaks.

Make sure to remove the plate on top and clean the holes.