What's the Best Way of Testing the Spark Plugs without an OBD Reader?

XJS Facelift with 4.0L AJ16 Engine

 

Huh? You don't test spark plugs, replace them. As they are used, the edges of the electrode wear and round off, that makes it harder for the spark to jump.

There is no way to test a plug with an OBDII reader.

 

DITTO

 

Most repair manuals have a page dedicated to multiple photos of spark plug conditions at the tip. They show normal conditions, too lean, too rich, etc. You can compare them that way. But from what I've seen in my past several days of research, if you already have them out, go ahead and gap check and replace...unless you have an inline 6 model, those look waaaaaaaay easier to replace lol

 

Hi OB,

I think to test them properly they have to be tested under compression. I think garages used to have machines for this but these days spark plugs are probably regarded as consumables and just replaced.

Good luck,
LeeP

 

They probably came in useful for those old Oldsmobiles or Buicks, whichever ones that you had to essentially pull the engine to replace. I could see a tool like that coming in handy.

 

Hi Matt

AJ16 is an Inline Six Engine

 

 

Hi Robman

I did exactly the same and got a reading of Zero Ohms on all of the Six Plugs which was what I was after