Not a "hesitation" but more of a "stumble"...

[Gregg Benedict]

So, after doing some work on my '58 Imperial, I'm getting a weird stumble at times when driving it. It's kind of hard to describe it. The car idles great, and also accelerates great from or stop or while kicking down the transmission in passing gear. However, occasionally it stumbles, mostly while flat cruising at speed. The stumble is seems like the engine looses power for just a split second, then immediately recovers. You can even feel it, like one of the cylinders missed. The other thing is, it doesn't always happen. One cruise, everything is fine. On a another, I might get 2-3 of these stumbles. I'm hoping some of you gurus out there might have some experience with this and what it might be. Unfortunately, I have a feeling it might be a myriad of things.

Things that were replaced: Spark plugs, spark plug wires, distributor cap and rotor.

It still is running on the points distributor, and that might be the problem, but I'm not sure. However, the points were recently cleaned up and adjusted. I want to go with an electronic ignition before the year is out. I also still use a generator.

 

[413]

Absolutely nothing wrong with points, the car ran points until now, how do that happen?

Did you check the timing? Was the distributor out to replace points?

Is the vacuum advance connected and working?

Advance the timing and go try it.

 

[Lefty71]

There are many possibilities there. I had a hot coil make weird troubles on me, and another time the single wire from the points had the insulation rubbed off barely touching the distributor shaft..... I suspect some fuel related issues could trip you up in a similar fashion.

 

[cbarge]

Check the advance weights to see if they move free. If stuck, it can cause a stumble upon accelerating.
Check all screws and nuts holding down the carb and carb body. A vacuum leak can cause a stumble.
Loose wires at ignition coil can cause a stumble.

 

[Gregg Benedict]

Note that the stumbling mostly happens when just cruising down the road... not necessarily on acceleration. I did not have the distributor out... just re-gapped the points and put on new cap and rotor. I did change the timing a bit to account for the use of modern gas, but that is it. I did put in a new hot coil, with anticipation of changing over to electronic ignition. You really think that could cause all this? I will put in the old coil, as well as check that all the connections are tight. I will also make sure the carb is down tight and look for vacuum leaks.

 

[413]

If you changed the point gap you changed the timing. Try advancing the timing and see what happens.

 

[mrfury68]

I did put in a new hot coil,

An old timer gave me this piece of advice about 45 years ago and it has saved my hide quite a few times over the years. " A bad coil will give you the same symptoms as a carb or fuel issue." I would put your old coil back on and see if that makes a difference. Always re-trace your work if you have an issue that didn't exist before. I learned that myself over the years. The new parts nowadays are no where near the quality of the parts they are replacing. I've heard of too many instances of parts failing right out of the box or shortly thereafter.

 

[Camshaft]

That's good advice! I had the same issue with my 67 300, driving along, then stumble and almost die. Went through entire fuel delivery system, same problem, started going through electrical from front to back and found a cracked wire to the coil inside the spade connector. Put on a new one, and all is well. CamShaft

 

[Gregg Benedict]

So, I put the old coil back on. The new coil I was using was a Pertronix Flame-Thrower PNX-40011. I also checked the wiring and found the wire to the positive terminal to be a little loose on the blade connector to the ballast resistor. I re-crimped the wire to a new blade connector to remedy that. All other connections looked OK. I also checked the nuts on the carb were tight on the manifold. I also decided to put on a new fuel filter, since I didn't like the clear see-through plastic one on there. When all was put back together and I started the car, I noticed that the fuel inlet nipple threaded into the carb was leaking... enough to get the carb wet. I tightened that down with a 3/4" wrench and managed to stop the leak. Could that have been the problem? The car idled and revved up fine afterwards. I would take the car for a drive, but the rainy weather is keeping me from taking the car out of the garage for the time being.

 

[Just Carbs]

You are describing an occasional but complete interruption of the ignition primary system.
That can be caused by a failure in the amp gauge or any wire going to or coming from it. Leave the head lights on all the time while driving and watch the amp gauge.
Put a timing light on the coil output wire going to the distributor and place it in the car where you can see it.

A low fuel level in the carb itself would present other more often and consistent symptoms. As in under hard prolonged acceleration.
Trash in a carburetor fuel circuit would also present as a constant aggravation.

 

[Polara_500_Jr]

I fought a similar problem for quite a while. ran great idling, and under acceleration. "Cruising" especially 2k-3k RPM it would stutter or stumble. I had a freshly rebuilt distributor, a new carb, but a very old coil. Since I was in a time crunch I replaced the points with a pertronix and the coil with another pertronix. fired up, timed it and the old beastie runs as well as I ever remember now. Kind of wish I had started with just the coil now but since it's installed it's staying that way now.

 

[Gregg Benedict]

I did manage to take the car for a test drive. It still has the occasional stumble. If anything, it is slightly worse than before. As far as the amp gauge goes, it does not work. I assume it has been bypassed, but it is hard to get a look at the back of the thing. Can a jumper wire just be routed across the ammeter terminals? I wanted to get a Pertronix electronic ignition put in, but the mechanic I first used couldn't get the car to run right with it installed. So, it got switched back to points for the time being. I was going to try and get an entire new distributor for the engine: PerTronix Flame-Thrower Billet Distributor Chrysler 392 ci Hemi, Part Number: 751-D144700. But, I hate to throw more big money into this thing without truly knowing what the real problem is. Could a bad ignition switch cause this kind of problem? How about a bad ballast resistor?

 

[Gregg Benedict]

You are describing an occasional but complete interruption of the ignition primary system.
That can be caused by a failure in the amp gauge or any wire going to or coming from it. Leave the head lights on all the time while driving and watch the amp gauge.
Put a timing light on the coil output wire going to the distributor and place it in the car where you can see it.

I was wondering about this. My ammeter does not work. I assume it has been bypassed, but cannot tell for sure since it is hard to feel behind the dash board. Can a simple jumper wire across the ammeter terminals be used to bypass the ammeter? Or, should I bypass the ammeter entirely by running a wire from the generator to the voltage regulator?

 

[Just Carbs]

I was wondering about this. My ammeter does not work. I assume it has been bypassed, but cannot tell for sure since it is hard to feel behind the dash board. Can a simple jumper wire across the ammeter terminals be used to bypass the ammeter? Or, should I bypass the ammeter entirely by running a wire from the generator to the voltage regulator?

An ammeter bypass? Sure, very popular.

 

[Just Carbs]

These GM style HEI distributors for the Mopar big block work smashingly well for $100.

 

[Polara_500_Jr]

I did manage to take the car for a test drive. It still has the occasional stumble. If anything, it is slightly worse than before. As far as the amp gauge goes, it does not work. I assume it has been bypassed, but it is hard to get a look at the back of the thing. Can a jumper wire just be routed across the ammeter terminals? I wanted to get a Pertronix electronic ignition put in, but the mechanic I first used couldn't get the car to run right with it installed. So, it got switched back to points for the time being. I was going to try and get an entire new distributor for the engine: PerTronix Flame-Thrower Billet Distributor Chrysler 392 ci Hemi, Part Number: 751-D144700. But, I hate to throw more big money into this thing without truly knowing what the real problem is. Could a bad ignition switch cause this kind of problem? How about a bad ballast resistor?

This is interesting. I have little distributor experience and installed the pertronix ignition into my distributor and had it running in just over an hour. Just from the so-so printed instructions in the box.

Just saw your location... I was just there for Mopars in the park, and come down there quite often, 3.5 hour drive Howdy sorta neighbor

 

[Gregg Benedict]

This is interesting. I have little distributor experience and installed the pertronix ignition into my distributor and had it running in just over an hour. Just from the so-so printed instructions in the box.

Just saw your location... I was just there for Mopars in the park, and come down there quite often, 3.5 hour drive Howdy sorta neighbor

Hey there... not sure I met you there or not. I brought the '58 Imperial to Mopars in the Park this year in the Fin Class. Before this year, I was always in the C-body class.

 

[Gregg Benedict]

These GM style HEI distributors for the Mopar big block work smashingly well for $100.
View attachment 723134

I doubt this distributor will work, as I have a 392. The distributor is in the rear of the block. Also, the heater box is still in place and would likely not allow for such a large aftermarket distributor to fit.

 

[Gregg Benedict]

So, I'm beginning to wonder if the problem is in the ignition switch or the wire to the ignition switch itself. To test this, I was thinking on running a temporary wire from the ballast resistor to the starter relay to bypass the ignition switch. I'm not sure if this alright to do. Also, would it be best to connect to the positive wire connection on the starter relay to the battery, or connect to the IGN. point on the starter relay? I'm guessing I wouldn't be able to stop the engine after starting it without removing the wire.

 

[mgm1986]

This does sound like an ignition related issue.

Do you have an ohm meter you could use to test the ballast resistor? You could also get a new one. They're not real expensive and never a bad idea having a spare in your trunk if you plan to stay with your current setup.