76 dart 318 stumble, miss, under load or high rpm

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Ferdinandbites

Ferdinandbites

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Need your help. Have a 76 dart 318 and it has this, difficult to explain, let's say stumble, miss, pause, from the engine, cold or hot engine, under higher rpms( reving engine) and a load. I'll try to spell it out if u will on how it would sound, lol, here I go miss, miss, miss miss miss, miss, miss miss. Well, u get the idea. Not in that exact order. No banging or popping sounds. U can feel it when u r driving almost like on a boat when the wind blows and holds the boat back a bit. Like a misfire but random and can't locate it to any particular cylinder as if it were a bad plug or wire. The engine runs very well outside of this issue and you'd never know there was a problem.

I've rebuilt the carb and it made the engine run smoother, better acceleration, idle but no difference for stumble. It's no longer dropping fuel into the intake.
New ballast resistor, because there was also a problem with it starting and stalling once the key was let off but that has been resolved.
I've replaced the spark plugs, ignition wire set, cap, rotor, (it's an electronic ignition), fuel filter, air filter.
It does have an electric fuel pump aftermarket but the fuel pressure is within spec. I think it was within 8-15 psi something like that just can't remember.
Erg stays closed and opens when temp switch on rad warms up.

I have looked through a number of files here but I'm new and can't seem to locate a search icon to type some key words to c if others have run into this. My apologies.
I appreciate your time, suggestions and expertise on this one I'm stumped.
 
These can indeed be difficult.

1. "Rig" a way to run it with a voltmeter on the 12V (key) side of the ignition ballast, and make sure you have good solid voltage while running. this should run "same as" battery CHARGE voltage, 13.8--14.2 warm, not below 13.5, and not above 14.5

2. Examine / wiggle distributor shaft for wear and wobble. Check the reluctor gap. .008 inches with a BRASS feeler. O'Really's used to carry these

3 any possibility? The ECU can or has gotten wet around the heat sink? this used to be a problem for me with my old 4x4. I don't like throwing money, but in this case, might be worth scaring up another ECU.

4. With air filter removed, hold throttle at different RPM "steady." Look and listen at carb throats. Should not visibly be "dropping" fuel, and should not spit IE should not sould like bacon frying "in the carb."

5. Have you run compression / leakdown tests?

6. What plugs you running where are they gapped and how do they look?

7. Does it start good? Have you checked the spark?
 
67Dart273 said:
These can indeed be difficult.

1. "Rig" a way to run it with a voltmeter on the 12V (key) side of the ignition ballast, and make sure you have good solid voltage while running. this should run "same as" battery CHARGE voltage, 13.8--14.2 warm, not below 13.5, and not above 14.5 same as battery voltage

2. Examine / wiggle distributor shaft for wear and wobble. Check the reluctor gap. .008 inches with a BRASS feeler. O'Really's used to carry these no wear or wobble, gap is at .008

3 any possibility? The ECU can or has gotten wet around the heat sink? this used to be a problem for me with my old 4x4. I don't like throwing money, but in this case, might be worth scaring up another ECU. its dry, ground off the rust, no difference, tapped/hit the exam to hear if it affected the problem and no.

4. With air filter removed, hold throttle at different RPM "steady." Look and listen at carb throats. Should not visibly be "dropping" fuel, and should not spit IE should not sould like bacon frying "in the carb."no longer dripping after I rebuilt the carb still no difference. No bacon.

5. Have you run compression / leakdown tests?no I didn't check yet. Shouldn't I hear and feel problem at all rpm if this was the case?

6. What plugs you running where are they gapped and how do they look? .0035, oem, no difference

7. Does it start good? Have you checked the spark?
Click to expand...
now it does after I replaced the faulty ballast. No difference.[/

today I went out and jiggled the connectors on the firewall, not sure what they r called right now and boom runs like a charm again. Couldn't wait to take it out and sure enough I was able to tear up the pavement once again. Oh it's nice to be able to do this again. I dare not touch those wires again but if it should happene again I will pull the connectors off and check them out, clean lib ect.

I really appreciated your help and guidance. U gave me things to look at that I didn't think of. I hope I cross my fingers on this one for now that it stays like this..
 
No, none of us have ever had to deal with an engine miss before. :D

You really should pull that connection (bulkhead connector) and clean those contacts at the very least.
It can cause a lot more problems than a miss.
 
Ferdinandbites said:
I have looked through a number of files here but I'm new and can't seem to locate a search icon to type some key words to c if others have run into this. My apologies.
I appreciate your time, suggestions and expertise on this one I'm stumped.
Click to expand...

Looks like you've gotten some great advice already Ferdinand!!

The "SEARCH" button is at the top of every page in the black header ^^^ for future reference....Welcome :thumbup:
 
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