Hello all, I am running out of hair to pull out on this issue. I had a nice running 06 x350 Super V8.. right up until I did a battery change. The battery was out for about an hour or so, place the new battery, connected..and then the madness. First the car would not idle, but would idle OK while in gear. Drove it around the block, while monitoring electric power with a monitor, 14.4 volts, she stalled at some stop signs, still idle was erratic while in park, surging from 500-1000, put in gear drove. Seemed to get better as I drove her around the area, nothing hard, just nice and even. Then at one stop, alternator power went to minimum, 12.8 volts at idle, and 12.5-12.9 at 1500 rpm, no lights on dash, no messages. Drove home directly and parked.
Battery charged overnight. Drove round the block again, 14.5 volts for a bit, 10 minutes later, back to 12.5.-12.9 at 1500 rpm or so, returned to home. Is this how the alternators fail in these? My auto has 115k on her. Not sure if it has been changed. I am used to either working or not working, but not this working for a bit, and then fail, next day same. Suggestions? Thanks in advance.

 

That is unusual. My try would be the computer fix. Unplug it and then plug it back in. In this case remove the battery terminals for a bit and then reconnect. Some people say to connect the positive and negative cables together while they are off the battery which discharges energy storage capacitors in the ECU. I have done that to no ill effect. Just off the battery.
Then, there is a procedure somewhere in the forum about how to reset/restart after a battery change. I have attached the one I have but it says 2003.

 

Hi, why did you replace the battery in the first place? Was the old battery not charging or not holding a charge? If so then I would guess that the new battery is also not being charged properly so you may have replaced the old battery when in fact the alternator is the problem and is not charging properly. A failing alternator will give all sorts of strange issues. Are there any noises coming from the alternator area and is the bearing on the alternator smooth or does it feel rough when rotated?

 

The battery was old, with a date code of 3 year ago, and on top of that, went dead (forgot to put on the maintainer) So, placed a new battery. There is a new noise, sounds like a supercharger whine but not as sexy in the engine bay, so I will have to put it up on the lift and see.