Can your battery affect how the engine runs??
 

A mechanic I took my corvette to told me the battery I had (a cheap everstart battery) was making the engine idle rough even though it starts it just fine? Reason I ask is because this is the battery I actually use in my Jimmy. Is it true a battery could affect the how the engine is running? Or it this dude full of $%@!

Theoretically it COULD affect it, but I don't buy it without an explanation. Prove it to yourself; fire it up and unhook the battery. If the rough idle goes away then the mech is right, if it stays then its obviously another problem! Your battery just acts like a voltage buffer for the alternator when the engine is running. You could always hook a multi-meter to the battery while the engine is running and look for serious fluctuations. Compare those results to not running. What happens to the idle when you turn on your headlights or turn signals? If the engine stumbles then your battery may be on its last legs, but could also be your distributor contacts/plugs/wires are corroded.

Hope it Helps!

I have personally not heard of this before. From my understanding, once the car is started, it runs off the alt. So I cant really see how the battery could effect how your car runs.
on a side note, Yay, Ugg boots.

From my experience, yes he is. Once an engine is running, the battery is out of the loop since the power is being provided by the alternator.

Like everyone has said this guy is full of $^&*%.Now if your altenator is bad it wil.I have a voltage check on the Alenator.Clean off your battery connections and make sure they arent corroded.

I'll try it out tonight and post what i find! thx