Isolated miss, while cruising, only at 1400-1500RPM

[Propwash]

Hey fella's,

The bird recently seemed to develop a little hick up. Every once in a while, when cruising at about 30mph (right at 1400-1500 RPM) the car will have a slight miss. It doesn't stick around or repeat, doesn't buck the car, is very light. It might happen 3-4 times of a half hour of cruising around. I pulled the dist. cap and the arc strikes are at the very edges of the contacts in the cap, and looking at the top of the rotor, it looks like the arc did some wandering. One thing I did notice is that the shaft has some sloppy up/down play. Like 1/4" inch sloppy.

I'm just starting to troubleshoot this. This is something that has started in the past month. To me it seems like a definite ignition issue. There is no other sign of this issue at any other RPM or while giving her the berries through the 1400-1500 rpm range. The distributor is from 4 seconds Flat, custom curved and phased for this motor, and is set at 22* initial and 36* total. It was dyno tuned for this timing going off torque/HP curves, vacuum and Exhaust gas temps.

Any ideas out there?

 

[Hemi Rebel]

How are the plugs and wires? Sounds like a wire may be arcing to ground. Maybe got a little too close to exhaust.

 

[miller]

Might check the carbon button contact in the center of the cap. Sometimes those things can break. Also make sure your spark advance is working smooth, not dragging or hanging up.

 

[Danomt]

Are you using any vac advance.???

 

[Coyoteduster]

If the wires are older, I would start there.

 

[Propwash]

Thanks fellas!

I'll check the plug wires and boots. They're Less than a year old Firecore 50's with fiberglass socks over the boots. I wouldn't think i'd have an issue, but it sure doesn't hurt to check the easy stuff, you never know. To me the cap/rotor seem kinda cheap. Is there any higher performance cap rotor out there any of you fella's would recommend? As far as the advance, it's mechanical...no vacuum.

 

[Gpuller]

Yep its junk, I'll take the headache and figure it out.
Had a buddy with the same ignition set up and chased a miss like you describe. He ended up changing the whole system.

 

[747mopar]

Hey fella's,

The bird recently seemed to develop a little hick up. Every once in a while, when cruising at about 30mph (right at 1400-1500 RPM) the car will have a slight miss. It doesn't stick around or repeat, doesn't buck the car, is very light. It might happen 3-4 times of a half hour of cruising around. I pulled the dist. cap and the arc strikes are at the very edges of the contacts in the cap, and looking at the top of the rotor, it looks like the arc did some wandering. One thing I did notice is that the shaft has some sloppy up/down play. Like 1/4" inch sloppy.

I'm just starting to troubleshoot this. This is something that has started in the past month. To me it seems like a definite ignition issue. There is no other sign of this issue at any other RPM or while giving her the berries through the 1400-1500 rpm range. The distributor is from 4 seconds Flat, custom curved and phased for this motor, and is set at 22* initial and 36* total. It was dyno tuned for this timing going off torque/HP curves, vacuum and Exhaust gas temps.

Any ideas out there?

Imagine that, if you figure it out let me know because my car is doing the EXACT same thing to the T. Sounds like the ignition just shuts off for a split second while cruising at 30 mph then runs perfectly fine and like you said it's very light. I talked to a buddy who works on cars for a living and he suspects it's the mechanical advance and that I should switch to vac advance for better control (operates off the engines needs). I'll be watching because it's annoying as hell.

 

[Propwash]

Imagine that, if you figure it out let me know because my car is doing the EXACT same thing to the T. Sounds like the ignition just shuts off for a split second while cruising at 30 mph then runs perfectly fine and like you said it's very light. I talked to a buddy who works on cars for a living and he suspects it's the mechanical advance and that I should switch to vac advance for better control (operates off the engines needs). I'll be watching because it's annoying as hell.

I'll keep you updated 747...I should find sometime this coming weekend to tinker with it.

 

[nm9stheham]

If you want to check the plug wires, use an ohmeter on a higher resistance setting. If any of them have significantly higher resistance end to end than the others, then chuck it. I read up on the Firecore50 construction but can't tell you exactly what range of resistance to expect for that type, but for a standard RFI suppressor wire, 1,000 to 3,000 ohms when new is normal; when they get near 10,000 ohms, they are failing.

 

[68sportsatelliteragtop]

Had a similar issue last summer. It would come and go, then got progressively worse. After chasing my tail a while, I replaced cap and rotor and that cured it. I had to hunt for Blue Streak parts, not sure if it was worth the trouble, as they are also thin. Got a spare set in the car......

 

[Propwash]

If you want to check the plug wires, use an ohmeter on a higher resistance setting. If any of them have significantly higher resistance end to end than the others, then chuck it. I read up on the Firecore50 construction but can't tell you exactly what range of resistance to expect for that type, but for a standard RFI suppressor wire, 1,000 to 3,000 ohms when new is normal; when they get near 10,000 ohms, they are failing.

Had a similar issue last summer. It would come and go, then got progressively worse. After chasing my tail a while, I replaced cap and rotor and that cured it. I had to hunt for Blue Streak parts, not sure if it was worth the trouble, as they are also thin. Got a spare set in the car......

Thanks Gentlemen. Both those are easy & cheap to accomplish, and i'll be trying out this weekend hopefully. Thank you for your input.

 

[gtxno1]

here is something simple and quick if suspect leaking wires or cap you can use a spray bottle of water and ammonia spray the wires and cap area's this will highlight your problem very quickly if indeed it is the issue the arc's will start jumping

- - - Updated - - -

here is something simple and quick if suspect leaking wires or cap you can use a spray bottle of water and ammonia spray the wires and cap area's this will highlight your problem very quickly if indeed it is the issue the arc's will start jumping. the resistance of the wires can still be good but still leak

 

[sleepar]

Dual points will find its way home....

Laugh and chuckle but nothing beats points....

 

[Propwash]

Dual points will find its way home....

Laugh and chuckle but nothing beats points....

That is worth a laugh and a chuckle Sleepar. I'll let you gather and relish all the dual points you can muster. Myself, no way. That's like going back to salting meat instead of using a fridge.


Replaced the cheapo cap/rotor with a Blue Streak set (Made in America!!). Anyways, no miss to be had. I can't say 100% that was the fix (being the car didn't do it a couple drives before the change), but I would lean towards yes, being I have driven it a lot since the (without a miss), and cars generally don't fix themselves. Thanks gent's!

 

[sleepar]

Points or not I had issues with every cap and button except for Taylor in brass...
I like the msd wires and coil... I don't have big horse build so I keep the points... I will agree the electronic is better when it does work... and I can be full of $hit but a Taylor cap and button will work flawless... US point folks need all the help we can get.

 

[Propwash]

The Blue Streaks are in Brass as well. The old one was just aluminum. Not impressed with the quality of it. Thanks for the tip on the Taylor's. Hoping the change cured the issue. As far as points, I remember being on the side of the highway, about January and 20 some below zero. Frozen hands......well frozen everything, using a Zippo for a light and trying to set points with the backside of a matchbook. Good times...good times... Naw, sorry man, just don't see myself going back.

 

[747mopar]

I was really hoping you'd find something else Prop for my sake but that's great news. I've already changed my cap and rotor, they're Mallory parts with the brass terminals. Guess I'll give them a second look and keep on looking.

 

[Sonny Black]

Prop,I think cap:eusa_think:

 

[WP29440SE]

don't know what carb you are running , but it sounds like a lean condition. just for shits , you could try another running carb just to rule out fuel delivery.

I had the same issue running a 1407 edelbrock carb. changed the metering rods and springs to a tad richer (I had leaned it way out) . I also took out the counter weight on top of the checkball below the squirters, also putting the accelerator pump rod in the top hole. all my missing issues are gone through the whole range.