High RPM problems.

[ninjazombiemaster]

Today was the first day in a while that was dry enough for me to really drive the Z vigorously and safely. I noticed that my car is losing almost all power at 4000 rpm. The stuttering sound it makes is like its run out of gas, but then it starts backfiring. Seems like both from the exhaust and intake at times. This only happens above ~4000 rpms, in all gears. It idles fine, and drives fine at low RPMs. Since I haven't been driving it in that fashion real recently, I'm not really sure when the problem started. However, the car has a new rotor, distributor cap, pertronix ignitor, alternator upgrade and battery. I really feel like its an ignition problem. I immediately suspected fuel, but leaning or enriching the carbs only makes it idle bad and still have the problem. I replaced my fuel filter, which was a little dirty and checked the last chance filters, and were both clean. Float levels haven't changed, so those shouldnt be running dry. Besides, fuel has to be getting somewhere for back and afterfire.

If I had to guess when the problem started, I'd say when the pertronix was installed. I suppose the unit could be defective, or maybe I don't have it connected right (though I'm pretty sure I do). I also believe, and correct me if I'm wrong, but an ignition like the ignitor is more likely to be effected by a failing coil than points. I'll double check my plugs, but they we're good 2 days ago when I looked last. The plug wires didn't have any visible arcs that I could see, so I don't suspect them, however I do consider it a possibility. They are the NGK plug wires we all know and love. I did try swapping the coil wire to a different one with no luck.

My suspects are:

The Coil: I'm going to test it if possible tomorrow. If not possible, I may just replace it anyway.

The Electronic Ignition: If the coil tests good, or a new coil doesn't resolve the issue...

Any other suggestions or ideas on what I should check tomorrow?

[madkaw]

Coils are cheap to replace and eliminate . Make sure you have the proper impedance coil for the Pertronix .

Did you check the mechanical advance on the dizzy to make sure it was operating freely?

Sounds like leanness could also be a possibility .

[240260280z]

spark scatter from a loose part in the distributor?

early spark pops in the intake

late spark pops in the exhaust

for fuel:

lean pops in the intake

rich pops in the exhaust

[Zed Head]

Isn't one advantage of the Pertronix, over other electronic ignitions, that you can pop the points back in easily? Might be a quick way to test the Ignitor.

[ninjazombiemaster]

Coils are cheap to replace and eliminate . Make sure you have the proper impedance coil for the Pertronix .

Did you check the mechanical advance on the dizzy to make sure it was operating freely?

Sounds like leanness could also be a possibility .

Tried choking it, same problem. Also still happens with enrichment. Vacuum advanced works, but I'm not certain of the mechanical. I'll check, thanks.

spark scatter from a loose part in the distributor?

Maybe. There's a wire that appears to be a ground wire from the condenser. Its not real loose, but maybe when things get spinning... Theres also a notable amount of metal dust from the old rotor and cap wear. I'll hit it with condensed air.

Isn't one advantage of the Pertronix, over other electronic ignitions, that you can pop the points back in easily? Might be a quick way to test the Ignitor.

Yes, and I intend to try that. However, if the coil is bad, and the ignitor is only making the problem apparent, putting the points on would only be a bandaid for the failing coil.

[madkaw]

Choking it doesn't help if the float levels aren't high enough.

Do an ohm test on the coil?

[Zed Head]

Yes, and I intend to try that. However, if the coil is bad, and the ignitor is only making the problem apparent, putting the points on would only be a bandaid for the failing coil.

Sounds like you're going to buy a new coil anyway so it doesn't really matter which you do first. A coil is probably cheaper than a new Ignitor. Good luck.

[ninjazombiemaster]

Choking it doesn't help if the float levels aren't high enough.

Do an ohm test on the coil?

Float levels shouldn't have changed, and we're set perfectly this summer. I can check again though.

I slept in too much to test the coil today, but I will tomorrow. I've got the day off.

Sounds like you're going to buy a new coil anyway so it doesn't really matter which you do first. A coil is probably cheaper than a new Ignitor. Good luck.

I suppose your right. And yes, about 7x cheaper. Haha. Thanks!

[ninjazombiemaster]

Used a lab scope on my ignition. I was seeing 50k+ volts at idle. Yes, you read that right. My theory right now is that for some reason the car is demanding way more voltage than the coil can produce, and at high RPMs it can't keep up, power goes away, and when we can get a spark, it misses. Tried low resistance wires, just as bad. Put the old cap back on, just as bad. Spark plugs look good still. Gotta get back to work and order a new coil before the parts stores close...

[madkaw]

Measure ohms resistance?

[Zed Head]

Great that you took the time to find a scope and use it, but I think that you were looking at the wrong things. Voltage is not "demanded", it is produced, or available. Current could be considered to be a demand item, it is a function of resistance and voltage. The 50,000 volts that you measured is about normal for some coils, but could be a sign of too much current through the coil and module (the Ignitor), which could be caused by a bad ignition module or low resistance on the coil's primary circuit. As madkaw suggests, have you measured resistance on the primary circuit? Maybe you just need a resistor in the line. If you get a similar coil you might just end up with the same problem.

[madkaw]

I think you should be around 1.5 ohms MAX on the primary and as low as .7