Hello there,

’92 facelift V12 distributor ignition US spec (air injection)

When idling the left hand exhaust gives a steady flow when you put your hand over it whereas the right hand exhaust pipe does not.
To diagnose the cause of the presumed misfire on the A bank I listned to the injectors by means of a stethoscope and all were ticking happily.
To check spark on each of the spark plugs on the rh bank I used a timing light and all ht leads induced a stroboscopic light as it should except for lead #1. I disconnected the lead from the spark plug en plugged it to a spare spark plug and grounded it to a convenient point and that gave a bright blue spark. Next I used a spark indicator light which goes inline between the ht lead and the spark plug in cylinder #1a and that also gave result. But still the timing light picks up a spark signal on all 5 cylinders except for #1.

What should be my conclusion from this?

 

Well if you suspect the #1 on RH side of engine, disconnect the lead completely and feel the exhaust again and see if it stayed the same or if it got even worse. If it got even worse move on to the next plug so on and so forth. Just an idea. Good luck. Someone smarter will be right along.

 

Tried that today. Didn’t make things clear. They all seemed to do the same. Could be an injector thing maybe. Disconnected every injector one by one but did not notice any difference.

 

I had that problem on an older Mercedes and used a timing light with the same result. Turns out the spark plug was bad - cracked insulator. A quick way to check is to move the plug to another cylinder and check again with the timing light. If the problem moves to the new location, you have a bad plug.