[DML] More ignition analysis

["cruznmd" <racuti1@xxxxxxxxxxxx>]

This post is for Phil P. who says he's following my ignition 
thread. :)

Recap: My car stutters as if from mis-firing (especially when pulling 
away from a dead-stop). All ignition components (plugs, wires, cap, 
rotor, ballast resistor, coil, ignition ECU) have been replaced 
without effect. Timing advance, both vacuum and centrifugal have been 
checked to perform correctly. Timing is set correctly, and was tested 
plus & minus the normal 13 degrees. The ballast resistance is 
correct, the coil resistances (both primary and secondary windings) 
are correct, the input voltage to the coil is correct. The coil is 
Bosch. Putting the old OEM coil back in doesn't correct the problem. 
All connections have been cleaned with contact cleaner and di-
electric grease has been applied. Grounds have been checked and new 
stainless hardware has been applied.

After speaking to several people, taking several readings and 
replacing several parts, I will now focus my tests on the pulse coil 
(in the distributor):

The pulse coil generates a voltage as it spins, the faster it spins, 
the higher the voltage (DeLorean tech manual). Simply put, the ECU 
reads the pulses and converts this signal to a control signal which 
drives the coil. The car runs somewhat better when cold, especially 
in the morning. If the pulse coil is outputting a poor, weak, signal 
(such as while turning slowly at idle) the ECU may output an 
incorrect control signal to the coil. Garbage in=garbage out. The 
pulse coil resistance should be 500 to 700-ish ohms. I will get the 
engine good and hot, and if the resistance is substantially higher or 
lower than this, I'll replace the pulse coil. I will also read the 
output voltage from the pulse coil when cranking the engine. I have 
to check what it should be. 

Other owners have written me who are also having this problem. None 
of us have really checked the pulse coil so we'll see what happens.

Rich A.
#5335




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