Lucas 45DM6 dizzy vs. Pertronix in 1986 XJ6
 

Sorry if this has been covered, I searched but couldn't figure out something.

Can someone please explain to me how installing the Pertronix Ignitor, shown in the photo, into my Lucas distributor (which is not worn out, <30000 mile and has new cap and rotor) can improve the spark? I understand how Pertronix would be an improvement over points, but how so on the constant energy ignition in my car?

The engine idles at 950-1000 in neutral, and in drive with foot on brake the idle is so lumpy it shakes the car. I have new plugs (gapped 0.035 for the cat) and leads.

I got an answer right from Pertronix. They would not claim a hotter spark or improved performance with the original Ignitor kit, as in the photo above, or the whole distributor D17600. They do say their system is more reliable than OE.

Further, Pertronix said that using the Ignitor II kit or distributor D171618 with their coil would provide an improved, higher output spark.

Greg,

The OE ignition system should work just fine at idle. Adding an aftermarket disty is usually done to improve higher performance at the top end (above 4000 RPM or so). You can check the air gap between the distributor shaft and the pickup coil which should be around .014 and you can check the pickup coil resistance which should be 2500 to 4500 ohms. Pull the amplifier plug and stick the test leads into the distributor, polarity doesn't matter. If those things are OK, then the only way to diagnose the problem is to replace items such as the amplifier, pickup coil, drive resistor etcetera, one at a time until the fault is found. If none of this helps then check fuel delivery, and believe it or not, valve clearance. I had an 85 with 2 intakes were so out of adjustment that it would not IDLE but "seemed" to run OK at higher RPM. After the valve adjustment, the engine performed much better not only at idle, but across the entire RPM range.

Steve

Thank you very much, Steve. I'm not too concerned about over 4000 rpm because I almost never get there! It'll take a while but I'll check all of the items you mentioned, though I have just been over the fuel delivery system and am happy with it. I am intrigued by your mention of valve clearances and will definitely get to that--great idea.

Rookie error: the spark plug leads were shorting out, severely on #4 and 5. Me ol' Dad made me pull them off one at a time while the car was running then had a jolly good chuckle when I got whacked by the spark voltage. New leads and she's no longer missing.