"85"CFI Merc runs good,then runs then runs like crap and won't start for a while.

[Mercuryman]

The distributor shaft seems to be snug.I used a spark tester and it does have spark after it stalls.I'm having a difficult time getting the old oxygen sensor off.For some reason my oxygen socket doesn't fit the oxygen sensor.I've used the oxygen sensor socket on my other 85 Merc and a 2003 dodge neon and it worked fine.This sensor seems smaller then the O2 socket.I've tried other deep sockets,but they can't grip the sensor because the top part is bigger than where the socket fits on.

Thanks for all the input so far.

[Mercuryman]

Hey guys,I finally got the oxygen sensor off!!I ended up busting off the top part of the old oxygen sensor off with a long chisel and a hammer.Then I was able to fit a socket on it,for some reason a metric 22 socket fit better than the standard 7/8 in. O2 socket size(probably because the old O2 sensor was slightly rounded off).I also noticed on the factory O2 harness connector,that there was 1/4 in. of exposed copper.It looked like either the insulation got pulled back or the wire was comming out of the connector.I tested the connector with a multimeter for continuity.I put one prob on the exposed copper and the other prob inside the connector,where it would connect with the O2 sensor connector.At first it didn't have continuity,but if I wiggled it,the connector sometimes would have continuity.So I cutt out the factory O2 connector and I put a bullet connector on it,to insure a good connection.I let the Merc run for 20 min. and it didn't run crappy or shut off.Hopefully the problems gone....


Thanks again for the input/suggestions

[Mercuryman]

I thought I would give a long overdue update! Replacing the O2 sensor did fix the problem of it running crappy after 6-7 minutes!I've been using the car since I replaced the O2 sensor and have not have had that problem.
Although in the winter when it's really cold out I've had the opposite problem.The car will misfire and run really rough for the first 5 minutes after starting.After about 5-7 minutes it will smooth out and run normal.I'm not sure if that would be O2 related or something else?I've replaced the ignition module on the distributor with a new one from Napa and it didn't change anything.