72 charger warm issue

[SNKEBIT]

Working on a 72 Charger 400 auto. Runs awesome before it warms up. Plenty of power, will power brake easily. After warming up, starts missing a little and no power. Will stall putting into gear.
Have changed out all ignition components 3-4 times with new stuff. Bought a new wiring harness from year 1 and did not cure problem. (thought had wiring issue with original stuff.)
Checked voltage at bulkhead on start and run wires, 13+ volts hot or cold conditions.
When it is doing the missing, I can run a hot wire to the coil and problem goes away.
Coil has 7+ volts on hot side hot or cold when in run mode.

At a loss here, 3-4 new coils, 3-4 new ign modules, 2-3 new distributors, new harness, wtf?

lol Never had this issue before. Don't want to leave 12 volts to the coil all the time, burn stuff out.

Any ideas I am missing?

 

[Bb70charger500]

How is the balesc resistor? I had one worked fine hit a bump barley worked..... Yours might be just hanging on !

 

[SNKEBIT]

Think I have it figured out. Previous mechanic played around with stuff and wrecked the coil, (which was new,) probably because the ignition harness had bad wires in it.
So, I had to fix 2 issues and backtrack other mech's issues.

 

[SNKEBIT]

I recant my last statement. After thinking I had it figured out, gave back to owner, problem came back.
Does the coil have to match the "ignition system"?
I have not been able to check system since, but sounds like coil failed again.
At a loss right now.

 

[SNKEBIT]

Ballast resistor brand new............

How is the balesc resistor? I had one worked fine hit a bump barley worked..... Yours might be just hanging on !

 

[Nacho-RT74]

Does the coil have to match the "ignition system"?

theorically and supposelly, yes. BUT I have run my car with regulars ECUs and HiPo coils ( along with regular and HiPo Ballast resistors ) and backwards and I can't say I did notice a failure related to a "mismatched" ignition components.

fuel and ignition failures are sometimes pretty much similar.

 

[beanhead]

When it is doing the missing, I can run a hot wire to the coil and problem goes away.

If you connected it directly to battery 12V, that narrows it down to the ignition coil (+) circuit...good start.
What I would do next, is connect your test wire to the coil when the problem starts and take it to each side of each component in that circuit (the ballast resistor, the voltage regulator, etc) until it clears up. That should pinpoint which part/connection/wire is causing the trouble.
And it bears repeating that unfortunately "new" doesn't mean "good"...

 

[Bee1971]

At a loss here, 3-4 new coils, 3-4 new ign modules, 2-3 new distributors, new harness, wtf?


What Brand coil - ECU - Distributor ?

Yes you can mismatch all this Chinese junk today , and have issues , trust me


I would follow what Bean said

 

[SNKEBIT]

IAnd it bears repeating that unfortunately "new" doesn't mean "good"...

I am a mechanic, I have said that to MANY customers over the years.

 

[furious70]

The big thing to insure is that you have an ignition driver and coil meant to run at the same voltage, e.g. stock stuff running at 9v or aftermarket running at 12v, and then either ballast resistor or no.