I have multiple cylinder misfire codes (x308 xj8) and I decided to check the resistance and ignition coil‘s to see if any are bad. Most tests just involve measuring the resistance between the pins and I went searching for that in this forum.

I saw the diagram someone had posted about measuring voltage between pin 1 and ground (pin 4???) and I cannot make heads or tails out of it. I did measure the resistance between pins 2 & 4 and pins 3 & 4.

2/4 most measured ~1000ohms and 3/4 were 32k ohms. Three coils measured over 82k ohms for 3/4. No coil pin 1/4’s measured any resistance.

Are the three at 80k ohms bad? ¯\_(ツ)_/¯

 

It is not really possible to test the coils with an ohmmeter as they have electronics inside so the ohmmeter actually reads resistances through the electronic circuitry, not through the coil windings. Due to this, the resistances measured may also depend on the orientation of the ohmmeter probes on the pins. You may have obtained 32 Kohms on pins 3/4 of 5 coils using one orientation of the probes and 82 Kohms on the 3 coils with opposite orientation of the probes. To compare the ohm readings between the coils, you have to keep the probe orientation the same on all coils like red probe on pin 3 and black probe on pin 4. Here's the diagram of a Denso 4-wire ignition coil from another engine, probably also applicable to the Jaguar coils:



Your detected misfiring could be simply because of failing spark plugs so, if already high mileage, replace them first. Otherwise, about the only way to determine which coils are faulty is to read the codes. Then swap the shown misfiring coils with good ones and see if the codes move. This will confirm the bad coils.

 

You can get a COP tester.

May be cheaper to swap some things

 

Get ebay set I bought set for about 100$ it's still working since a year . If you want oem and higher quality I believe NGK is better than DENSO , NGK coil set less than 600$ in ebay