03 Rubicon manual transmission, had its battery sapped by a problem with my CD player. Jumped it to start, idled at 1k rpms (higher than normal) for several minutes then died. Checked battery, held 12.3 volts, turned key to check fuel pump and it kicked on. Vehicle starts right up then rpms will drop to ~300 then putter out. Started it again, kept rpms at around 1800 and it would rev up around 150 rpms then go back to 1800. Battery was at 14.1v when running at 1800 so it’s not the alternator. No engine codes other than downstream o2 sensor that’s been there a month or so with no issues, no evap leaks is what I’m getting at. Any ideas? Would my TPS go bad overnight? Clean my IAC? I appreciate all help in advance.
Engine dies on idle
- Thread starter Toby42
- Start date
The engine will NOT idle or run for long once the battery goes dead. And with a dead-enough battery the alternator will not be receiving enough power from the battery so it can charge the battery.
Modern Jeep alternators require 12 volts from the battery to power them, yes I know that sounds odd but true. You can jump start a dead battery to get the engine running but once the jump start battery is removed, it won't run for long on the dead battery.
Yes older cars and Jeeps could run forever with a dead battery once it was jump started but those generators and alternators did not require power from the battery. Modern alternators REQUIRE 12 volts from the battery to put out enough power for the ignition system and to keep the battery charged. Modern alternators cannot be used to recharge a dead battery.
Charge your battery over night and it'll probably be ok tomorrow. If not have the battery load tested so you'll know its true health. Once a battery has been drained dead more than a few times it'll lose its ability to hold a charge.
Modern Jeep alternators require 12 volts from the battery to power them, yes I know that sounds odd but true. You can jump start a dead battery to get the engine running but once the jump start battery is removed, it won't run for long on the dead battery.
Yes older cars and Jeeps could run forever with a dead battery once it was jump started but those generators and alternators did not require power from the battery. Modern alternators REQUIRE 12 volts from the battery to put out enough power for the ignition system and to keep the battery charged. Modern alternators cannot be used to recharge a dead battery.
Charge your battery over night and it'll probably be ok tomorrow. If not have the battery load tested so you'll know its true health. Once a battery has been drained dead more than a few times it'll lose its ability to hold a charge.
Thanks you for the reply @Jerry Bransford ill put a trickle charger on it overnight. But I ran into another problem. I had my torque wrench on the wrong setting when tightening down my intake manifold bolts after cleaning it out. I stripped one, you know of a good work around for that? Retap and buy slightly bigger bolts?
Don't use a trickle charger which doesn't put out enough amps for a dead or nearly dead battery, you want a full-on battery charger. Trickle chargers are for keeping a battery charged, not recharging a dead battery since they don't put out enough amperes.
I can't offer much help on the stripped threads, are they in the head or on the bolt? Assuming it's in the head, you'd have to remove the intake manifold and then drill/tap the hole in the head and insert a helicoil threaded insert then use the same size bolt that was originally used.
Looks like I’m in the market for an actual battery charger then! I appreciate all the help. This is my 3rd TJ, but my first one I’m doing a lot of work on so I’m learning a lot. My wife calls it a money pit but it sure is a lot of fun!