Stuttering

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Yote

Yote

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Re: 1972 Demon 340
My engine seemed to be what I can best describe as stuttering, (missing) . It is most noticeable at 40-50 mph and after being warmed up. Has a new coil, rebuilt carburetor , just set reluctor gap to .010, think it should be set at .008 but didn't have brass gauge that size. It ran just slightly worse before adjusting air gap. Not running bad but still not right. I am thinking maybe a new ecu or reluctor and pickup. Would like to hear from those more knowledgeable than me .
Ps. Plugs and wires are believed to be near new (400 mi) by PO. Plugs are dry and light tan when pulled
Yote
 
So you verified your firing order a couple of times already, right?:D
If the plugs are all evenly colored I would have to think it's a fuel or timing issue but with so little info to go on it kinda hard to suggest anything.

Does it miss at idle, and would you know it if it was?
Does the problem go away under any circumstances, like more or less RPM or throttle?

Try to be as specific as you can about the conditions when it does this.
 
Too much vacuum advance? Reluctor gap should be 0.006 or is that for the cylinder clearance on my Dan Wesson.....
 
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Gap should be .008 and check your advance plate for binding. Id also say check your fuel filter but that would make the plugs look white as it would be running lean. Maybe look closely at your cap for cracks or traces.
 
mguner said:
Too much vacuum advance? Reluctor gap should be 0.006 or is the for the cylinder clearance on my Dan Wesson.....
Click to expand...

Could very well be, and that's why I asked about being more specific.
.006 is for your gun, .008 is for your weapon. :D

Boy did that come up out of the past for no good reason. :D
 
possible debris in needle valve? my 750 qf slayer was doing same thing, found little piece of rubber fuel line in secondary needle valve
 
New rebuilt carb (150 mi.) 19 degree initial advance timing, starts and shuts off well. New fuel filter. Distributor cap near new,clean and no cracks. Firing order checked twice. Miss would be almost unperceptable to most non car guys. Ecu was pretty warm, just to the point that you could still comfortably still lay your hand on it, much warmer and I wouldn't .
Yote
 
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I also include looking at the ignition system in the dark (night) with no artificial lights nearby. I have found spurious shorts on plug wires, coils, and spark plugs that way.
 
Got headers? Check your wires on 5 & 7, they are tight there and like to burn through. Take them off the plug and bend them around.
 
I take it you have tried pulling the timing back just a little?
 
Do not have headers, stock exhaust manifold . Negative on retarding the timing. Where it is set is where it seems to like to run, but I will take your advice and give it a try. Also does the ecu normally run as warm as I have described ???
Yote
 
Yote said:
Do not have headers, stock exhaust manifold . Negative on retarding the timing. Where it is set is where it seems to like to run, but I will take your advice and give it a try. Also does the ecu normally run as warm as I have described ???
Yote
Click to expand...
2 things i can think of that happened to me in the past. first is the coil overheating. in that case , replacing it with a known-good coil will solve the problem. also, it could be a broken distributor collar. to check it, remove the distributor and inspect the plastic collar that is located underneath the distributor
on the shaft. when it breaks, timing becomes unstable. maybe you could diagnose it with a timing light.
 
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