my 86 se 2.8 is running very rich. there is a strong unburnt fuel smell and the rear bumper is covered in carbon soot from the exhaust. where do you start on these cars? the cat has been taken off and one of the donut gaskets is bad, idk if this has anything to do with it?

Is the Check Engine light on? How long has this been happening? Did it start all of a sudden? Did you make any changes to the engine that we should know about?

my check engine light is burnt out and i havent made any modifications to the engine. when i got the car i did plugs, wires, cap and rotor, air and fuel filter, thats all. it has a high idle too, about 1500 rpms hot and cold.

well, first thing you should do is replace the bulb in the check engine lamp and pull the codes because it will probably be lit. It's not hard to replace the bulb, a few torx screws on top and two 7mm (i think) bolts on the lower part of the dash, one on each side to remove the back of the dash pod.

Sounds like a vacuum leak and/or an exhaust leak.

If you have a bad enough exhaust leak, the O2 sensor will see too much oxygen, and the computer will think the car is running lean and dump in more fuel.

If you have a vacuum leak it can cause a high idle, and the computer can get confused thinking the throttle is open a bit more and dump in more fuel.

So, I would start with those two things, and replace the O2 sensor just to be sure.

If none of those things get it, check your cold start injector to make sure it's not stuck open.

i wouldnt worry about the idle first since a lot of our cars run that high but for the running rich i would replace your ecu temp sensor first. after i rebuilt my motor which had sat in the car for 10 years in a friends back yard my car was running very rich so i hooked up a scanner and it said the my coolant temp was zero so i replaced the temp sensor cleaned my plugs(which you should do cause i know that they are fouled running that rich) and the sensor only cost me $9 and instantly the car was running 100%

the last two posts are very good, all the more reason to see if the ECU is throwing a code. fix the light first.

Get that light replace and check for the codes.
The second thing I would do is check the fuel pressure and do a leak down test on the fuel system.