hi guys im in need of a bit of wisdom, i have a 1990 ef8 b16a and on idle it sounds really rough and as if it is not runing 100%. i have brand new plugs and have checked the leads are working which they are, when i pull the leads off starting from no.1 the car dies, no.2 car dies and no.3 the car dies but when i pull no.4 nothing happenes no change in sound and no fluctuation in the revs which leads me to belive the car is running on 3 and there is a problem with no.4 cylinder, so when i pull 1,2 or 3 the engine is only running on 2 and cuts out? what should i be checking next?

cheers sandy, scotland

 

Pull the plug in #4. After running the car for a while on 3 cyc, the 4th plug should smell of fuel. If not, look to the injector (or wiring). One quick test, swap injectors #4 and a known working one, like #3. Restart. If problem moves to cyc with swapped injector, you know it is injector, if not, you know to move to your next step.
Make sure you don't have a faulty plug wire, check for spark too.
Then, compression test.