Hello , My car is a 1980 Jaguar XJ6 S3 4.2L.

Question:.. can a new pickup coil be faulty despite having a correct static ohms reading between 2.2 and 4 kohms?(it has 2.7kohms on 20 deg day)

Situation:
The car had difficulty starting, finally figured it was the PICKUP COIL after failing ohms test intermittently.
I bought a new pickup coil AEU1500. I tested the new pickup coil on bench, its between 2.2 and 4k ohms.looks ok.

I also changed other items while waiting for the pickup coil.
New ignition coil (lucas)
New Rotor in distrubutor
New ignition LEADS set 8mm.
New ignition module in amplifier.( i have a few, have substiuted them a few times, same result)
New spark plugs
Freshened up the distributpr, cleaned oiled it etc. Vaccuum works ok, sucking on the spigot moves baseplate 2-3 degrees or so.

Since i installed the new Pickup coil , the car will start ok, and now seems to idle ok(it seems its better with the new leads than old ones, it was rougher with them) but if i apply throttle, it misfires on cylinders, engine jumps...becomes unstable. No matter how much i swing the distributor, its always unstable. It cant become stable/tuned.
I dont think a poor vaccuum advance would cause a misfire and the engine to jump... i tested vac hose etc.. looks ok. If i sucked on the vacumm spigot , it moves the plate 2-3 degrees...so looks ok

The spark plugs on inspection were ALL black, some more than others. This lead me to conclude a lack of spark to burn the fuel, or the timing
on the distributor was way to late.

Pickup coil GAP is between 8 and 14 thousands. There is no wobble in distributor shaft.

I do recall that if i increased gap to 14 thousands area, ie set it wider, engine became better, more stable .But applying throttle still produces misfires and jumpy engine.

I do know i dont have a "flash sheild " in distributor, never have.. others say its not an issue, most dont have one.
I though maybe on throttle , spark was arcing due to lack of flash sheild?.. possibility, not sure.
Some times spark arcs due to a bad rotor.. but i substituted the old rotor, spark plugs, leads, distrbutor capp etc. one at a time . with my old an new stuff.. nothing changed.

Im suspecting
1- the new pickup coil may be faulty.
I did an ohms test on the bench, again its ok between 2.2 and 4 k ohms.
I cant yet substuitute my old pickup coil as the old pickup works intermittently. Currently its not working as it doesnt have the correct ohms reading on it, so i cant use it.

Question:.. can the new pickup coil explain this jumpy engine and be faulty , despite having a correct ohms reading statically.?
A parts dealer said he had many problems with the pickup coils, but he said the fault would show up with a static ohms test. This one passes that.

If i have to assume the new pickup coil is OK... i am only left with changing the wires from igntion amplifier to ignition coil.... continuity test shows there ok, BUT i may as well change that.

Last thing would be an earth leak, so electricity doesnt get to coil/distributor on higher throottle.. so lack of spark, misfire? Just thinking out loud on that.

Any advice is appreciated.
regards
Peter

 

Seems like your ignition is sorted. Move on to fueling.
You can verify if it's a fueling issue by seeing if it will rev up using a combustible sprayed in to the intake tract. I suspect it may be the air meter as is often the case.

WARNING: Make sure your timing is right and be-sure to have an extinguisher handy and perhaps wear a fire suite, and consider having the car towed to a open field of concrete and have the local fire dept. on stand by. I like to use brake clean as its highly volatile and doesn't puddle. Good luck.