Couple of weeks ago while I was up in the woods cutting wood, I turned on the radio while we loaded/split the wood. After an hour or two we finished and went to head home, my truck turned over fine but wouldn't start. The tach wasn't moving so I figured "bad cps", then I installed my spare cps.
Still wouldn't start,checked fuses,relays,fuel filter etc. all looked ok. At this point I could tell the batteries were getting low, the dome lights would dim when the gp's were on. Jumped it from my buddies truck for a few minutes and it fired right up. Started in the morning for the next couple days and ran fine but seemed like it was cranking slower than normal. Kind of struggling to fire up. I went ahead and replaced the batteries (had old motorcrafts) with new wally world batteries. These were manufactured in Oct 05. Since I installed the new batteries it turns over a lot faster than before and starts great but now it doesn't idle as well as it did with the old batteries. Feels like
its missing . Anybody ever have this happen? Could it be because the batteries had sat for 5 months when I got them.? I'm sure they would test fine. Any ideas? TIA.

 

I would test both sets of batteries with a load tester to make sure they are up to snuff. I would also check the alternator to make sure it is up to snuff also.