Need help with missfire under load on 340

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Hopefully you found your problem.
 
71DodgeDemon340 said:
Pulled all the plugs and you can tell its running rich which is no surprise because it always has, but i noticed that the plug from number 1 had a crack on both sides. I split the porcelain off where it was split and it looks clean, no carbon tracking.

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with the porcelain split like that if it was arcing to the head i should of seen a carbon track correct? Or was it just dissipating the spark in the boot? I dont think i did it taking it out
 
71DodgeDemon340 said:
cap and rotor look good, plug wires are fairly new taylor thundervolt wires. Havent pulled plugs yet
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Well remember the old adage. "NEW" doesn't mean "GOOD. Here's what I would do to help eliminate some of that. Yes, it's one of those "old wives tales" to some of these damned experts around here, but IT WORKS. Wait till it's good and DARK THIRTY outside. Bust it off and let it warm up. Chock BOTH rear wheels. HARD. Get someone in the car to heavily set the parking brake and PLANT the brake pedal. Now you get under the hood, while THEY run the RPM up IN DRIVE. If you have some secondary ignition leakage, you'll know it right quick like. I would eliminate that first, because it's so easy to do and costs nothing.....well.....as long as you're careful. LOL
 
Years ago ('79ish) I had '71 Satellite (318 with 100,000+ miles) that with a ight throttle/pedal was OK, but heavy throttle/pedal it would stumble/sputter/surge. Took it to a repair shop and they replaced the worn distributor and all was good.
 
71DodgeDemon340 said:
Pulled all the plugs and you can tell its running rich which is no surprise because it always has, but i noticed that the plug from number 1 had a crack on both sides. I split the porcelain off where it was split and it looks clean, no carbon tracking.

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Well! There's a secondary failure if I ever saw it. lol It just "might not" carbon track if the path to ground was a REAL goodun. You know. As in LOW resistance? LOL
 
RustyRatRod said:
Well remember the old adage. "NEW" doesn't mean "GOOD. Here's what I would do to help eliminate some of that. Yes, it's one of those "old wives tales" to some of these damned experts around here, but IT WORKS. Wait till it's good and DARK THIRTY outside. Bust it off and let it warm up. Chock BOTH rear wheels. HARD. Get someone in the car to heavily set the parking brake and PLANT the brake pedal. Now you get under the hood, while THEY run the RPM up IN DRIVE. If you have some secondary ignition leakage, you'll know it right quick like. I would eliminate that first, because it's so easy to do and costs nothing.....well.....as long as you're careful. LOL
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cant do that with a 4 speed lol
 
71DodgeDemon340 said:
Also when i pulled the plug wire off the socket stayed on the plug, not sure if when it was crimped it cut the plug wire in half or broke it and allowed it to pull apart. They came pre crimped
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I am assuming you know the age old trick to twist the plug boot while pulling at the same time? I know most everybody does, but it doesn't hurt to ask. That's not surprising. Go back to my post where I talk about "NEW" and "GOOD". LOL

I remember when parts stores sold plug wire by the foot on spools. You just pulled off however many feet you needed, bought the boots you wanted and the ends and made them up yourself. We never had the problem of the ends coming off back then. Never. The good old days.
 
RustyRatRod said:
I am assuming you know the age old trick to twist the plug boot while pulling at the same time? I know most everybody does, but it doesn't hurt to ask. That's not surprising. Go back to my post where I talk about "NEW" and "GOOD". LOL

I remember when parts stores sold plug wire by the foot on spools. You just pulled off however many feet you needed, bought the boots you wanted and the ends and made them up yourself. We never had the problem of the ends coming off back then. Never. The good old days.
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yes lol, ive made a few sets of accel wires in the past. Im not sure if im going to try and recrimp that one wire or just buy a new set. Im deff going to get a set of plugs, may put wires on it too and go from there
 
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Plug wires should be here tomorrow, put a new cap and rotor on it as well, i did notice the female terminals of the ignition module plug were a slight green color, cleaned them up real well and applied some di electric grease to the terminals, not sure if that could cause a issue or not.
 
Remember too to put dielectric grease in the plug boot too and blob a little on the metal tip of the plug. This will help get the boot off next time and hopefully the metal end won't come off the wire.
 
RustyRatRod said:
Remember too to put dielectric grease in the plug boot too and blob a little on the metal tip of the plug. This will help get the boot off next time and hopefully the metal end won't come off the wire.
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thats the bad part i did last time but guess it wasnt enough lol
 
71DodgeDemon340 said:
thats the bad part i did last time but guess it wasnt enough lol
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Yeah, it needs to be a good little bit. On the boots to keep the spark from "leaking" and on the tip to hopefully keep the metal end from pulling off the wire. Hopefully. lol
 
71DodgeDemon340 said:
with the porcelain split like that if it was arcing to the head i should of seen a carbon track correct? Or was it just dissipating the spark in the boot? I dont think i did it taking it out
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did you crack that plug taking it out ? if that was cracked before - I’ll bet that’s it. Check all the plugs.
hell just put a new set in and drive it
 
I vote to throw these plugs away. They might idle ok. But as soon as you increase the throttle, the secondary voltage rises and then the voltage will start taking a shortcut across the soot. And after that you gotta fix whatever sooted up those plugs, or it will just happen again..


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Just came back from a test drive and the miss is gone! Thank you guys for all the advice and help
 
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