Distributor Problems, Missing on Cylinder #4 Options

[warrenoliver]

I just returned from a long weekend trip with some other PCA members. The weather was beautiful and we had a great time. My car did not cooperate. I have a 73, 2.0 with FI and Pertronix Ignitor ignition. I have had the Pertronix ignition for a couple of years now and I have had no problems. The problem I am having with the car is that initially it runs great while the engine is cold and while it is warming up. Once it is warmed up - about 7-10 miles, on country roads, it begins missing badly. The miss is not consistent and seems to get better on acceleration. When I come to a stop, the engine idles very slow (200-400 rpm) and sounds like a John Deere tractor.
I put a timing light on each of the spark plug wires and found cylinder #4 is misfiring badly. I thought maybe the wire was bad so I switched it with another cylinder and found that #4 was still missing. I had an old distributor cap and put that on thinking maybe it was a cracked distributor cap. The problem stays with cylinder #4 with both caps.
I am now thinking it must be either the rotor or the electronic ignition module. Tomorrow I will try a different rotor.
My question is: Does this sound like the electronic module is going bad? When they go bad, do they cause this intermittent miss? Any other ideas out there?

Thanks.

Warrenoliver

[michael7810]

I had similar problems when my rotor went bad. Look for cracks in the epoxy along the top between the center and end contacts. My car would idle OK but had no power and the miss would come and go. I bought the modified rotor from Aircooled.net that they replace the resistor with a solid copper wire and all is good.

[Mblizzard]

Typically the electronic ignitions are all or nothing (1 or 0). I had a similar problem and it was the magnet on the shaft had moved up somehow. Check that and the gap between the magnet and sensor.

[Dave_Darling]

Also check the plug.

--DD

[warrenoliver]

Typically the electronic ignitions are all or nothing (1 or 0). I had a similar problem and it was the magnet on the shaft had moved up somehow. Check that and the gap between the magnet and sensor.

I lost the little plastic feeler gauge that came with the ignition module. Do you know what kind of a gap it needs?

[warrenoliver]

Also check the plug.

--DD

Dave,

I didn't think of checking the plug itself - I will check it in the morning. If the plug is bad, wouldn't there still be power coming down the plug wire as shown by my test light? When it is idling and missing badly, I can see the light pauses occasionally.

[TheCabinetmaker]

Could be a bad connection from the wire to the end. Pull the wire, and unscrew the end. cut a half inch off the wire, and screw the end back on.

[warrenoliver]

Update on the problem:
I removed the spark plugs and found #4 to be fouled, the rest looked good. I replaced with a known good one. This did not fix the problem.

I removed the electronic ignition and replaced with my spare points - did not fix the problem.

I removed the distributor and checked the points plates. I found the ground cable was broken so I thought that was the issue. I replaced with a set of plates with a good ground cable. I was sure this was the fix but it still misses although not as bad as before. (IMG:style_emoticons/default/headbang.gif)

After I replaced the distributor, I realized I didn't check the fuel injection points. Guess that is the next step. When I check them, how do I test to see if they are working?

One thing that has changed, it seems the miss is no longer on #4 cylinder. I can't tell which one is missing because it doesn't do it at idle anymore. It still runs great until it is completely warmed up.

Any advice?

[mgphoto]

Typically the electronic ignitions are all or nothing (1 or 0). I had a similar problem and it was the magnet on the shaft had moved up somehow. Check that and the gap between the magnet and sensor.

I lost the little plastic feeler gauge that came with the ignition module. Do you know what kind of a gap it needs?

just needs to be an air gap, thickness of the tip of a flat blade screwdriver.

[TheCabinetmaker]

Pertronics says the air gap should be .010 at the bottom, and no more than .060 at the top.

[warrenoliver]

Pertronics says the air gap should be .010 at the bottom, and no more than .060 at the top.

Thanks for the info on that. Right now, I am back to points until I can get this darned thing running right again.

[michael7810]

Did you replace the rotor?

[warrenoliver]

Did you replace the rotor?

Yes, one of the first things I did along with the distributor cap.

I changed the coil today and found a chunk broken out of the insulation of the relay board. I stuffed a towel under the board to keep it from warming up and took it for a drive. I drove about 20 minutes without any engine miss. The last 5 minutes I removed the towel and within minutes, it began to miss. I am now leaning toward the relay board but I need to drive it some more to see if I really have narrowed it down to that.

[rhodyguy]

914sixer is selling a recon and tested board in the classifieds. On page 2.

[warrenoliver]

914sixer is selling a recon and tested board in the classifieds. On page 2.

Thanks (IMG:style_emoticons/default/piratenanner.gif)

warren