Electrical Problem - erratic idle speed
Thread Starter
On The Tree
Joined: Jul 2005
Posts: 186
Likes: 0
From: near Philly
Electrical Problem - erratic idle speed My son just replaced his battery with a Red Top Optima 2 months ago. Two weeks ago, the battery went dead at a friends after a few hours. He eventually charged the battery to 12.2 volts (Optima says it needs 12.9) and after starting the car, he's getting 14.0 volts on the battery which means the alternator is working. However, when he tries to step on the gas, the idle goes crazy, dropping to 300 rpm, going up and down. He cleaned the terminals and retightened them, but still the same problem. He's made mods to the electrical system, added stuff, etc, so I suspect it's one of the mods, but he says he disconnected them with the same problem.
I suspect something is "on" when the car is turned off which is draining the battery, which is one problems, but the crazy idle may be a 2nd one.
The last time this happened, the problem disappeared the next day and worked well for 3 weeks. Is this electrical or something with another problem? We took it to the dealer and it didn't throw any codes. Could a defective battery do this (that would be news to me), or is it in one of the mods he did (which is what the dealer thinks).
The fact it didn't throw any codes has me perplexed. Any help would be appreciated!!
I suspect something is "on" when the car is turned off which is draining the battery, which is one problems, but the crazy idle may be a 2nd one.
The last time this happened, the problem disappeared the next day and worked well for 3 weeks. Is this electrical or something with another problem? We took it to the dealer and it didn't throw any codes. Could a defective battery do this (that would be news to me), or is it in one of the mods he did (which is what the dealer thinks).
The fact it didn't throw any codes has me perplexed. Any help would be appreciated!!
TECH Senior Member
Joined: Dec 2001
Posts: 5,399
Likes: 3
From: Jacksonville, FL
Something's going on, probably not the Optima since it's new - easy enough to check though, just bring it back to where it was purchased and have them load test it. When the battery is disconnected the PCM resets and idle needs to relearn, but should only take a few minutes, if he disconnected it again right after to check/clean the terminals it starts over and has to relearn all over again. Never go to the dealer just to check for any codes, places like Auto Zone will do it free.
