My 66 coupe started a while back having a sporatic slight miss, mainly at startup. It was not anything that I was concerned about. Lately, now that I'm driving the car more, the problem has gotten worse.

Now (especially at start-up), the miss causes the radio to temporarily shut off at the same time as the miss. And this morning the radio stations in memory (AM/FM/Cassette) were erased during the cut out as I pulled out of a Sunoco station, and the car later wanted to cut out at a light as I was accellerating.

The cables on the battery are tight and the connections are clean. I'm thinking maybe a bad cable or grounding strap. Thoughts? I'd hate to start replacing parts without having a better idea of the possible cause. TIA!

 

Sorry for bumping but this was pushed back to page 3, and last night I relaized that our DD blew out the t-lok. So we are down a vehicle and I could use our '66 if the problem was fixed. I'll offer a custom tag line (under their username) to the member who ID's the problem. :-)

 

Well, I'm thinking this could be 2 seperate issues. Where is your memory wire hooked up at. The radio memory is supposed to be a constant batt source, while the ignition feed would be switched power. I would take a look at the connections at the back of the ignition switch and the plug at the firewall. Is this a stick or auto?

 

It's a 289/auto. I don't remember where the power supply wire for the radio is plugged into (I installed the radio about 20 years ago), but I'll check it.

I'm trying to figure out why the entire system would cut out while the engine is running. I'll look at those connections. I know my recent taillight issue was the connector after the switch, and although it looked fine the connection was fragile. I guess that's what happens when you drive a car with wiring that's 42 years old!

 

It could be a loose connection at the ign switch or a bad switch also. ( if your using switched DC for your radio). There is also a main soldered together wire connection in the underdash wire harness that feeds battery into the car circuits that is fed from the wire that is attached to the batery side of the starter relay. (you may want to check there too)

 

Have you tested your alternator?

 

It could be the grounding strap, but how old are your battery cables?

The project stang in my garage had NO grounding strap, the previous owner had given up on the car because it would cut out randomly, he pursued this by hacking out all the wiring in the car and buying a new harness...that he never put in, BTW. The problem was a cracked grounding stud on the starter.

 

Sure does sound like a ground problem and because it does it when the car is running it seems likely it is between the engine block and frame. Find the ground strap and give it a good tug, looking for a loose or corroded connection.

 

UPDATE:

I checked the cables and grounding strap. All seemed tight, although the cable running to the solenoid probably should be replaced. The other terminal has a quick disconnect which unscrews (added years ago to keep the battery from draining). I was able to turn that about a half turn.

I had the idea to drive it at night to see if the headlights died when the car cuts out (if they didn't go out, then I would stop looking under the hood and look at the ignition switch). I drove it last night and of course it didn't act up. I'll try it again over the weekend too, but it could be that the disconnect was loose enough, or tugging on the cables brought things in check. Another thing I want to try is disconnecting the battery while the engine is running to see if it dies. The alternator is relatively new, the battery is 3yo, but these aftermarket voltage regulators (Made in China) are not known for their quality.

I'll keep y'all posted, cuz it could help somebody else down the line...

 

There's a common problem, suspect the power wire, or memory wire, to your radio is tapped off the 12V ignition wire under the dash. You've got an intermittent short. Follow your power wire back to the point where it's spliced, then trace both wires to determine if they're rubbing against a sharp edge and shorting to ground.