Random backfiring

[Jon Schmid]

My Roadster has developed a weird condition. It fires up fine, goes down the local roads/freeways just fine, then suddenly the engine stumbles and starts backfiring loudly through the exhaust. Then it catches again and will run fine, even up to 90 MPH (don't tell the CA Highway Patrol) for several minutes. Then out of nowhere, the same thing will happen. It seems like a fuel delivery issue but why is it happening so randomly? Has anyone else out there experienced this phenomenon? Plenty of fresh gas in the tank. Any thoughts? Thanks in advance---

[Dave Wildrick]

Make sure the connections to the spark coil are on tight. If the left one is loose, you will get power intermittently to the coil and backfiring when it rattle around. Then the engine will die when it falls all the way off the post.

[Jon Schmid]

Make sure the connections to the spark coil are on tight. If the left one is loose, you will get power intermittently to the coil and backfiring when it rattle around. Then the engine will die when it falls all the way off the post.

Thanks, Dave. That is one of the first connections I checked. I cleaned the coil spade with really fine grade sandpaper and then made sure the terminal was crimped onto the spade. I just rechecked and that connection was tight. I have already cleaned the points as well. What's weird is that the engine will run fine under all conditions including full throttle and then will start suddenly start cutting out before running fine again. Signs of a bad coil and/or condenser?
Again, thanks for any help--

[Ron LaDow]

I see a dead horse here, but just can't avoid whacking it one more time:
Try a complete tune up.

[David Jones]

Change the coil. If that don't cure it then change the condenser but also do a full tune up, but those two items would be my prime suspects for your problem. On the tune up include new points.

[Jon Schmid]

Change the coil. If that don't cure it then change the condenser but also do a full tune up, but those two items would be my prime suspects for your problem. On the tune up include new points.

Thanks, David. I replaced the points and condenser not too long ago and I have heard rumors that some of the so called new condensers are POS. I'll try to find the time to do a tuneup this coming weekend. Thanks again for all your input, I appreciate it.

[Kevin Wills]

Seems like mechanical things fail consistently and electrical things intermittently. I'd focus on the ignition circuit and spark. Swap out out components until you find the offender. Don't overlook basics like ground wiring and check every ignition circuit connector twice.

[Ron LaDow]

[...]Don't overlook basics like ground wiring and check every ignition circuit connector twice.

A full tune will make you look at all this stuff, so it's one reason it's a good idea.
And we're dealing with engines which are at least 50 years old and not driven as much as they were, so we end up with problems which are a result of a touch of valve clearance combined with some points that have worn just a bit much. You'll NEVER find that sort of stuff by random focus.

[Martin Benade]

Surely you would have noticed, but the distributer clips are on? I have had a similar problem from a loose cap once.

[Ron LaDow]

Surely you would have noticed, but the distributer clips are on? I have had a similar problem from a loose cap once.

Martin, did the loose clips suddenly allow it to function again?:
"...then suddenly the engine stumbles and starts backfiring loudly through the exhaust. Then it catches again and will run fine, even up to 90 MPH..."

[Martin Benade]

Maybe not exactly, but it was a really long time ago, I don't remember the details.

[Jon Schmid]

Surely you would have noticed, but the distributer clips are on? I have had a similar problem from a loose cap once.

Actually, in the 43 years combined that I have owned/driven my coupe and Roadster, that has happened twice, once on each car. And I knew right away something was very wrong because the cars suddenly felt like they were running on two cylinders and it was all I could do to get them to the side of the road. But thanks--I will check everything and I appreciate the inputs.

[Dave Wildrick]

If you are running the 050 distributor and have the orginal black rotor in there, it will give symptoms like that after the resistor inside heats up, which takes about 30 minutes or so of freeway driving. Replacing the rotor with the standard rotor from the cast iron distributor (for 018 or 022 distributor) solves the problem. I found out--but not before unnecessarily replacing the fuel pump, coil, and other things.

[Jon Schmid]

[quote="Dave Wildrick"]If you are running the 050 distributor and have the orginal black rotor in there, it will give symptoms like that after the resistor inside heats up, which takes about 30 minutes or so of freeway driving. quote]

Thanks, Dave. I'm pretty sure the rotor is that funny orange color. I'm far from an expert but I'm suspecting the coil but as suggested, I will tune up the car and not only look at the rotor a bit closer but also the distributor cap. Thanks again for all the suggestions--I appreciate the help.

[Lon Tusler]

Perhaps there is some moisture in the gas tank that's getting sucked up randomly?