bad alternator? erratic rpm needle / rough idle -
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Go Back > General Technical Discussions > Stereos, CB & Ham Radios, GPS, & Electrical. > bad alternator? erratic rpm needle / rough idle

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Unread 05-22-2013, 01:42 PM   #1
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Join Date: May 2013
Location: High Point, North Carolina
Posts: 18
bad alternator? erratic rpm needle / rough idle

I stopped and got gas on the way home yesterday and after I hopped back in I cranked it back up. Instantly it was running rough at idle and would sputter when I gave it gas. The RPM needle was literally bouncing around all over the gauge (almost like when you reset a cars computer and crank it up for the first time) but the engine remained idle but idling a little rough. Could this be a symptom of a failing alternator? My voltage on the gauge has always been below the 14v a little ways. It typically stays between the first line and the 14v mark but never exactly 14v even with everything off.

Since about March of this year I have put in a brand new battery in it back in March. Since then I have replaced 02 upstream, crankshaft position sensor, plugs, wires, rotor cap, ignition coil, ignition pickup, catalytic converter, muffler, exhaust manifold.

1997 Wrangler
2.5l SE

97wra is offline   Reply With Quote Quick reply to this message
Unread 05-24-2013, 05:16 PM   #2
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2005 LJ Wrangler 
Join Date: Feb 2011
Location: Dayton, Ohio
Posts: 2,330
First clean your battery terminals and connectors. Also clean the opposite ends of your ground connections. Your description sounds like a poor resistive connection. Your battery meter should be on the high side of 14 when running and 12.6 engine off. You could use a multimeter to verify.
"Never look down on anyone unless your helping them up"- Jesse Jackson
JPNinPA is offline   Reply With Quote Quick reply to this message

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