k2kane

Hoping someone can help me with this issue.

Completing restoration of '66 fastback with rebuilt 289. All is well, fires up good, idles good, but after warmed up and placed into gear, the engine has an intermittent miss, which sometimes causes the engine to completely stall. I've noticed too, that the missing and stalling increases when an electrical load is applied (turn on headlights, interior lights, etc.).

I've replaced distributor, coil, and all spark plug wires with known working setup (from another 289) and still having the issue. Any suggestions on next steps to isolate and locate the issue would be sincerely appreciated!

Special20

Sometimes a bad carburetor or a vacuum leak will cause these problems.

fastbackford351

You running points?

k2kane

No running Pertronix coil and distributor in both mustangs. Took coil, distributor, and wires from working car and out into this one.

k2kane

Yes I was thinking that but what's weird is why would it begin missing /stalling only when electrical load is added. Idles fine in gear until head lights or interior lights are switched on then begins to miss. I might swap carbs just to be certain, though.

Mr. D

Some shots in the dark, not being there to observe. Hope I don't insult with my questions & thoughts.

Is the voltage to the coil sufficient? How is the voltage level feeding the coil & for charging the battery? If you put the headlights on do they dim a lot when starting the engine?

Choke adjusted properly? Not staying closed when engine warm making the mixture too rich?

Does it miss when at high RPM?

If not, I would look at the idling circuit of the carb. It may need cleaning or rebuilding. With the other parts you switched, I guess you can switch the carburetor next!

If if does miss at high rpm too, I think I would now make sure you have consistent fuel supply & metering, that is clean fuel (no water in it) no air leaks on line coming from fuel tank to the fuel pump, a good fuel pump with consistent pressure filling the carb bowl, a clean fuel filter & accelerator pump, jets in the carb, etc. Switching the carburetor should check this. If a good carb still misses look for a problem from the tank to the carb like dirt, water, air leaks that could cause pumping air causing misses.

Good luck! You'll find it!

k2kane

Thanks for the questions. The coil, distributor and wires were all replaced by a complete working set from another 289 mustang - and the problem still occurs, so we can eliminate these components.

The voltage coming from the alternator (feeding coil/battery) has not yet been checked, but will check. I also haven't paid too close attention to lights when starting, but good idea, I will.

Choke is fine, car fires right up, choke on and then idles fine. Only when engine is fully warmed up do I notice the stalling. No, it does not miss at high idle. In fact, if I set the idle so that it's around 10rpm when in gear, I do not experience the issue, or at least I can't sense a miss and it will not stall out. I will swap the carburetor and see if this helps.

Thanks again for your response!