Fly Z28

95 Formula M6, bone stock. 87,000 miles. no leaks, not a drop of coolant from the water pump. it has been cranking sort of weak lately, then today I drive it 2 miles, get lunch, then 1 mile to friends house, park it there for 1 hour. go out to drive home and it cranks weak then dies about 1 block down the road. will crank and run, but stumbles bad when you presh accelerator and dies. let sit for 10 minutes, cranks up and runs like scalded ape.
any ideas? do they have a coil that may be acting up? like I said, opti is dry, no leak from water pump. alos the top was down and no A/C on.
Thanks, bret

slopokrodrigez

Since you say it's cranking weak, it sounds as though either the battery is extremely low or there is a wiring issue like a bad connection or corrosion. A wiring issue will act as though either the battery is bad or the alternator is bad. The first thing to do is check all the battery wiring from the battery terminals to the positive and negative cluster on the passenger fender to the ground strap from the frame to the engine and ground above the starter. All should be removed, cleaned and retightened.

Next put a voltmeter on the battery before and during someone cranking the engine over. Be sure the voltage does not drop below 11 volts. If so the battery may be on the way out. After the engine fires up, check the voltage again at the battery and be sure it's around 14 volts. If it's not, could be the alternator went south. If all that looks good, do one last check of the alternator output. Set the meter to AC and measure from the negative terminal of the battery to the output post of the alternator. Should read 0.03 or less. If higher, the diodes in the alternator may be going bad and leaking AC.

If you entirely eliminate the battery and the charging system, other things can then be looked at.