Not that anyone has been following this, but my daughter let the engine get
overheated on my 91 2.1 when the Temp II sensor retaining clip broke and
immediately emptied coolant. The head gaskets leaked and the thermostat
housing was warped, primarily, but I had some other troubles along the way
like a cylinder frozen to one of the heads.

Anyway, I made a mistake by letting a wire get caught under the driver side
rubber gasket, which cases coolant to pool on top of the cylinder. I can
take care of that. The engine, though, is exhibiting symptoms that I
thought I would ask about.

It was doing the same things before the overheating and gasket issues, so I
anticipate some troubleshooting will be in order when I get the gasket leak
repaired. Before I found the head gasket leak, I was able to run it to warm
and then drive it for three or four miles, so I can observe that the post
op problems are the same as the pre-op problems with the exception that the
effects of the leaks, except for the mistake on the DS rubber gasket, are
fixed.

Here's what's going on: when I start the car, it runs great. It just purrs
strongly and steadily, until it gets warmish and then it begins stumbling
and issuing some black exhaust like it's running rich. If you let it idle,
especially with it in drive and there's that little bit of extra drag, it
will stall. It does the same thing with the O2 sensor plugged in or
unplugged.

Any ideas?

Jim