misfire
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5th Wheeling
Joined: Oct 2022
Posts: 31
Likes: 1
Rebuilt dizzy, new plugs, cap, rotor, wires, coil.
I ran those auto lite 45 platinum plugs which is around the time the misfire happened. But I don’t know why it’s gotten so horribly bad lately. Plugs look fine and the coil is in spec for them. Might switch back to my old plugs or pick up some coppers as a last ditch effort to fix this. Misfire is across all rpm ranges. And is completely random even with plug rotation and I’ve plugged every vaccuum leak I can find. Few minor ones around the int man which makes sense but I might replace it soon anyways, if I ever get the 3500 around for the new head and full engine performance build later on down the road. I mostly want this truck just to make it down the road so I can move it 30 miles north to my shop.
I ran those auto lite 45 platinum plugs which is around the time the misfire happened. But I don’t know why it’s gotten so horribly bad lately. Plugs look fine and the coil is in spec for them. Might switch back to my old plugs or pick up some coppers as a last ditch effort to fix this. Misfire is across all rpm ranges. And is completely random even with plug rotation and I’ve plugged every vaccuum leak I can find. Few minor ones around the int man which makes sense but I might replace it soon anyways, if I ever get the 3500 around for the new head and full engine performance build later on down the road. I mostly want this truck just to make it down the road so I can move it 30 miles north to my shop.
FTE Legend
Joined: Nov 2015
Posts: 30,952
Likes: 4,126
From: Angier, NC
Rebuilt dizzy, new plugs, cap, rotor, wires, coil.
I ran those auto lite 45 platinum plugs which is around the time the misfire happened. But I don’t know why it’s gotten so horribly bad lately. Plugs look fine and the coil is in spec for them. Might switch back to my old plugs or pick up some coppers as a last ditch effort to fix this. Misfire is across all rpm ranges. And is completely random even with plug rotation and I’ve plugged every vaccuum leak I can find. Few minor ones around the int man which makes sense but I might replace it soon anyways, if I ever get the 3500 around for the new head and full engine performance build later on down the road. I mostly want this truck just to make it down the road so I can move it 30 miles north to my shop.
I ran those auto lite 45 platinum plugs which is around the time the misfire happened. But I don’t know why it’s gotten so horribly bad lately. Plugs look fine and the coil is in spec for them. Might switch back to my old plugs or pick up some coppers as a last ditch effort to fix this. Misfire is across all rpm ranges. And is completely random even with plug rotation and I’ve plugged every vaccuum leak I can find. Few minor ones around the int man which makes sense but I might replace it soon anyways, if I ever get the 3500 around for the new head and full engine performance build later on down the road. I mostly want this truck just to make it down the road so I can move it 30 miles north to my shop.
And then you said it started about the same time you used the fancy plugs.
Buy a set of good old copper plugs and I bet the miss will be gone.
Dave ----
ps some have had good luck running fancy plugs and others not so lucky so some may say it is not the plugs that is your call but I would run copper.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
I had a weird miss that I finally traced to a bad coil ground wire in the horseshoe connector. If you’re running an old horseshoe coil connector it might be worth a close look. Otherwise, agree you don’t want to run the fancy spark plugs in your old motor.
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
As you are a master Tech, it should be no sweat connecting a scope and investigating the engine health, Post a waveform of the ignition so that we can all see.
While you are at it perform an in cylinder running scope test...
While you are at it perform an in cylinder running scope test...
Cargo Master
Joined: Aug 2007
Posts: 2,561
Likes: 69
From: New Zealand
I've had exactly the same problem with that connector.
Two other random ignition miss problems I've experienced similar to the OP's....one was caused by worn distributor shaft bushes (but isn't your distributor new?); the other was plug wire routing causing induction crossfire.
The wire routing issue is well known with the V8 engines......I don't know regarding the 300 six.
FTE Legend
Joined: Nov 2015
Posts: 30,952
Likes: 4,126
From: Angier, NC
What shop has one sitting in a corner of the shop?
I have not seen one since the mid 80's
Dave ----
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Lead Driver
Joined: Apr 2002
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I've had exactly the same problem with that connector.
Two other random ignition miss problems I've experienced similar to the OP's....one was caused by worn distributor shaft bushes (but isn't your distributor new?); the other was plug wire routing causing induction crossfire.
The wire routing issue is well known with the V8 engines......I don't know regarding the 300 six.
Two other random ignition miss problems I've experienced similar to the OP's....one was caused by worn distributor shaft bushes (but isn't your distributor new?); the other was plug wire routing causing induction crossfire.
The wire routing issue is well known with the V8 engines......I don't know regarding the 300 six.
It's a good idea to get a quality set of wires. Cheapos should be avoided.
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