cylinder missing.. at limit on diagnosis

[zeichstein]

97 E420 was running rough and obviosly missing baddly...
had sulphur smell through exhaust....

pulled air filter... and coil covers....
used syringe with water to check exhaust manifold for heat.....

front cylinder on pasenger side is cold....

pulled coil and plug.....
plug is not wet....

started and coil and plug fire....

reassembled coil plug combo...

car runs smooth but still no heat on cylinder 1, and no sulpher smell...


did the computer cut off fuel to this cylinder?
if it was a fuel injector, how was it getting fuel.?
does the computer cut off any other cylinders when it detects one not firing to keep engine balance?

any help would be appreciated..

Thomas

[zeichstein]

used a better diag tool....

found it was the rear sets of cylinders...
unplugged coils one by one... all made a difference in idle except the rear two coils... would these cut off as a set?

[MrCjames]

To begin with, how is the engine harness? Does it have any signs of insulation cracking? If so you will need to replace the harness before going any further.

Now, as far as the misfire goes-the ME control unit is programmed to selectively cancel any cylinder "when" it counts approx 250 misfires in a predetermined amount of time. Once misfire detection counts 250 the ME control unit will selectively turn cylinders "off" in order to avoid damaging the catlytic converter. If the key is cycled "off/on" the cylinder will work until the misfire count threshold is met at which time the cylinder will be turned off again.

Try looking in all of the spark plug bores to see if there is any evidence of water and or corrosion from water resting in the holes. You can try swapping coils around to see if the misfire moves with the coil, if it does replace the suspect coil. You can also try changing spark plugs and you can try changing the coil ends to the plugs.