the other day i went out to take my stang for a spin and the battery died in it. so couple days later i bought a new battery and installed it now the car runs like crap. the car ran great then battery died replaced it and now it idles really rough and is sluggish when u hit the gas and sometimes you can hear it pop inside the intake. anyone got a clue what happened?

 

did you have the alternator tested??? if the vehicle is running off the battery it'll slowly drain it and and as battery voltage gets lower and lower the eec which requires the proper batt voltage could do wierd things if proper voltage does not remain constant to all elec systems

 

no i didnt have it checked out. the battery in it was pretty old. so i put the new one in and the idles up and down and when it does that the stock volt gauge moves up and down as well. it just idles really rough now.

 

If your volt gauge is going up and down with the idle. It's probably safe to assume it's charging.

 

you might need to test the new batt. it might have a weak cell or ground. with the volt gauge doing that makes me assume the batt isnt getting a good charge and the volt rise and fall with the idle speed of the motor. Remove, check,clean and reinstall the batt cables. also check motor to fram grounds while your at it.

 

How far did you drive it? You need to drive it 4-5 miles @ 45-50mph so the computer can relearn. Check your grounds, and make sure no hoses or wires accidentally got knocked off.