When Idle Voltage Drops and Engine Shuts Off

When I am stopped at a light or idle in general, in or out of gear, the voltage on my car drops from about 14.1 to 12.5 then to 12.1 and just turns off. I can get car back into park and turn car back on and it instantly turns on and ready to drive. (I have a cigarette voltage adaptor that shows voltage and allows me to plug in phone charging cables.)

When I first turn the car on and idle, the voltage reads 14.2 and then slowly goes down to about 13.1 over about 5 minutes. Everything is off - lights, radio, heat/cooling off.

I installed a brand new battery, new negative terminal cable (old one was so corroded and maybe had a resistance issue), new fuel pump, and a new alternator. Still, the issue persists. Any thoughts? Thank you.

What year Camry?

Tester

Sorry, 2003 Toyota Camry - 4 cylinder.

I can also add that when I’m stopped at a traffic light, I keep my brake on, but I have to use my other foot to apply the slightest amount of gas to the car to keep the voltage up till about 14 V.

Maybe the problem is related to some thing with the air intake or a vacuum seal?

I would try cleaning the electronic throttle body.

Tester

You should clean and tighten both ends of the positive and negative cables. not just near the battery. if the negative cable is clean by the battery and not at the other end it is not going to make a good ground.

Thanks! I may give that a try later today or tomorrow. I am leaning towards air related at this point.

The alternator was installed yesterday and I just took car for a somewhat long/fast trip on the interstate and car held it’s own at 13.5 to 13.7 volts, even when stopped at a light or parked in a parking lot. Maybe some sort of calibration or equalizing had to happen?

Thanks! I did clean the contact points (two of them for negative cable plus obvious battery terminal) when I put the new cable in. Screws also looked pretty good.

That’s correct charging system operation.

That’s not correct charging system operation. Maybe something about stopping is putting a big load on the electrical system. Stop lamp circuit is partially shorted to ground, wire pinched by brake pedal movement, etc. Another idea, when stopping, inertial forces cause front of car to pitch downward, rear moves up. The movement could be pinching a wire someplace. Ask you shop to check w/current meter to see if main current is going sky high when you stop.