Very weird issue.
2002 Ford Escape with V6. Engine died and would not start. OBD read cylinder 5 misfire.
Changed all plugs and ignition coils still no start.
While troubleshooting didn't have the # 6 plug in when engine was cranked and engine started. It will continue to start when a plug is removed.
Ford garage told that exhaust manifold cat was plugged from misfire and engine ruined because material in cat was sucked back into cylinder. Changed the 4/5/6 front exhaust manifold and cleaned cylinder which showed no damage and still will not start unless #6 plug is out.
Is there any sensor that would be reading a backpressure issue with the plug in? Has anyone ever heard is this occurring before?

 

Something you might check,
If you can remove the oxygen sensor, the one before the converter on the front bank .It should allow the exhaust to exit the same way removing the #6 plug is doing. If,,,,,,,,,it wiil now start with the #6 plug installed, you are looking at a converter replacement.
I would suspect that the misfire ran for quite a while , enough to plug the converter.
The check engine light should have warned that damage was on the way and am surprised it was not blinking to get the driver's attention that something bad was happening and damage was on the horizon. Could be wrong on this, but we have to start somewhere. Can you try this and let us know how you make out?

 

I replaced the exhaust manifold w/ cat on the 4/5/6 cylinder side (front of the vehicle) with a new one assuming that the cat was clogged. It should be as free flowing as normal at this point.
It's my teenage daughters car and she reported that the CE light started flashing right before it died.

 

Since the engine will run with the plug out , it would indicate it is capable of running.
I would still remove the o2 sensor for that bank and if it runs, there is a problem with a blocked exhaust.
There could be other possibilities, but we need to know if the exhaust is completely clear.

 

Thanks.

I planned on removing the Y pipe that runs from the manifolds to the cat under the car and trying to see if it starts then. I'll update after that.

 

Problem solved!

I did start with removal of the lower O2 sensor (blue wire) and with that removed, it started and ran with all 6 plugs in.

I then disconnected the exhaust at the Y pipe and Cat connection. As soon as I dropped the pipe there were pieces of the cat honeycomb falling out. After a good vacuum of the area in front of the cat and some air blown in, it is running again.

With the amount of material that was cleaned out it appears that the front cat disintegrated and had no whert else to go and plugged it completely.

 

Glad you solved the problem. Thanks for the update.