i have a 85-86 760GLE V6 it's got a loud tapping on the #4 or #5 cyl, this morning after about a 100 miles drive last night, i went out and started her up and she was idleing like cr@p, and the tach was swinging from 500 (allmost dieing up to a thousand or 1200).
so i figured i'd check to see if i had a lose plug and coulden't find any, so i pulled the #4 cyl spark plug, and started it back up,, it idled alot smother, could hear it missing but the engine wasen't sloping around like a dieing fish,
any body have any ideas?
the plugs are good,
the plug wires are good
all have good spark
or did (havent checked this morning)
i could use some help,
also unpluging the O2 sensor had no effect
althow unpluging a water temp sensor made it idle at 2000 rpm's
i need help, should i just sell the brick?



things i have allready replaced in the past 3 months:
power steering hose
both engine mounts
both fuel pumps
fuel filter
water pump
all fuel injectors
air filter
oil
oil filter
tires
light bulbs

I also meant to say that the intake valve spring may be broken or extremely weak and cause the same symptoms as a leaking or burnt valve. This would also explain the noisy engine.

Do a compression check on the engine. The #4 cylinder may have a leaking intake valve. The engine runs smoother when you pull the sparkplug wire off because there is no longer exhaust getting forced out of the #4 cylinder and into the intake manifold, where it screws up the rest of the cylinders fuel/air mixture. It would be like opening up the EGR(exhaust gas recirculation) valve at idle, the engine runs like crap because of the diluted air/fuel mixture. Good luck with the V6.