Because our cars are so dependent upon electronics and the proper voltages, having something amiss in the electrical supply can cause really strange behavior.

____Case in point, ... Yesterday, it was a beautiful day and I wanted to take the turbo Z28 out for a drive. It's not that many days till upstate NY will start getting snow so I want to use every excuse to drive the car
The car has been running great and today was no exception as I drove out about 15 miles on the rural highway. At that point, I decided to turn around and head off to the restaurant where I was to meet my wife for lunch. I pulled into a parking lot and turned around and waited for passing traffic to clear so I could pull out. Suddenly, the engine started running REALLY rough. I looked at my wide band AFR gauge and it was pig rich at 10:1. WTF? I pulled out onto the highway to see if it would clear up at higher RPM. Nope... Locked at 10:1 no matter what gear, MPH or RPM. Crap!! I pulled over onto the shoulder and popped the hood. All looked good so I went back to start the car. Shiiiiiitt.... dead battery.

___Sigh.. I called my wife, canceled lunch and asked her to bring some jumper cables. About 20 minutes later she arrived and I jumped the car. It started immediately and the idle AFR was 14.5:1. Perfect. Assuming I'd only have to drive the car a bit till it recharged, I took off the jumper cables. Phock.. the motor labored down and the AFR was back at 10:1. I killed the motor, locked up the car and had Jodi(my wife) drive me home to get tools and our other car.

____Jodi went back to work and I drove off with my tools and my multimeter. Arriving back at the car, I popped the hood and tested the voltage with the multimeter. Hmmmm... 12.5 volts while not running. Odd considering it didn't have the ability to even crank the motor earlier. I made sure the bolts to the battery terminals were not corroded and tightened them up. I tried to crank it. Wouldn't even turn the motor over once. So... I jumped the battery again and cranked the car. Started right up and idled like a champ. I used the multimeter to affirm the charging system was 13.5 volts. Sure was but I realized, that could be coming from my Vans charging system. I disconnected the cables and again, the motor labored down and died. I hooked up the cables and started my car again. Once again, it fired right up and idled/AFR perfectly. To test it, I pulled off the negative cable but hovered the cable just above it's terminal so that if the motor labored down, I could instantly reconnect the cable to the battery to see if the motor would recover w/o dying. This would tell me if it was purely the battery. Sure enough, it labored down, I hooked the cable onto the terminal the idle cleaned right up. So to me, it was the battery, no matter if the static voltage was 12.5.

____So off to NAPA I went (closest auto parts store by about 12 miles) and bought a $90 (w/core) battery. I was telling the guy behind the counter what was going on and HE felt that the real culprit was my alternator. He then tested my old battery to make sure it was crap. He hooked up some box to the battery and sure enough, it was toast.

____So, off I went install the battery. Afterwards, I cranked it and the motor fired instantly with perfect AFR. I took out my multimeter to test the alternator. If the alternator is working correctly, a multimeter should show 13.5 to 14.x volts at the battery terminals. Shiiitt.... it was 11.5. This meant that I not only had a bad battery but also a bad alternator. I called around to see if any parts store had one in stock. Most only could order one but one store (Autozone) had it but it was 27 miles away. Off I went. After $139 and my old 14 yr old Alternator for a core, I installed it and all was (finally) good.

Dave
my car:My Turbo Z28

 

Your first symtoms pointed to an alt to me as well. And a fresh battery would hide it..for a bit. Just sucks it was an expensive day for you-

Enjoy these last couple nice days- they aren't going to lasting much longer thats for sure...

 

Yeah. I'm DEFINITELY not going to try to drive it in the snow this year. Last year I had and absolutely seat chewing drive back home after unexpectantly being caught in a snow shower. I thought the car was going into the rails or a ditch about a third of the 5 mile drive home. Add to that, I got stuck on a hillside where I could leave the car in first, get out and push to get the car to complete the hill at about 1 mph. Phock that. Lol... I'll put her on jack stands under a car cover and start her periodically till spring arrives.

 

Here's another tip...don't ever pull the battery cable off when the engine is running. Modern alternators need the load to sense how much voltage to output. You can easily ruin an alternator by removing a battery cable. It was a common practice in the old days, but not any more.

 

Just to be clear, I pulled the negative jumper cable connector off the Van's battery. I didn't pull the battery cable off my Z28's battery during my test.

Thanks for posting this though. I do remember doing this on my old Dodge Demon 340 back in the 70's.

 

Honestly you will be better off by pulling the battery and letting it sit until you decide to bring it out. Not letting things get up to full operating temp will just invite condensation and then the rust to follow- esp in the exhaust system. I have pulled the battery in my car every year the past 10 yrs, went out in april put it back in and she fired right up everytime.

 

Good point and taken well. Thanks!

 

DirtyDaveW:
If you remove the battery for winter, in the spring, you might want to pull the injector fuses and crank the motor 10 or 15 seconds to push some oil around the system before actually starting the motor.

 

Thanks for another great idea