Running pig rich?

[fdekat]

Hello  Matt:

I've found that a 4K will run very rich, and give very bad milage if the ECU
ground (to the stud on the right side of the intake maifold) is broken, or
gone. This is a big "BTDT" !

-Frank de Kat-

>Hi all,

>Got the new fuel tank in my '86 4kq last Saturday and the car runs great. 
>Starts up every time without hesitation, pulls strong, doesn't cut out in
>corners, steady cruising is a breeze.

>The only problem is the car runs rich.  Really rich.  At any given time
>there's a fine black mist emanating from the tailpipe, more so when the car
>warms up.  At idle a nice haze forms behind me from the unburned fuel mist,
>and sometimes (not always) at 80% throttle to WOT I can see a cloud pouring
>out the tailpipe as I accelerate.  Also, as the car warms it will
>progressively idle lower and lower until it will die unless I jab the gas
>pedal.

>I've replaced the plugs recently and also the coolant temp sensor (the one
>at the bottom of the coolant neck leading from the head to the radiator). 
>If anything, the coolant temp sensor replacement made the problem worse, as
>before it would occasionally idle (albeit high, around ~1200 rpm) when warm.

>Any other theories?  Could it be the thermotime switch is faulty and my cold
>start injector is firing all the time?  I reasoned out the O2 sensor, since
>it still runs really rich at WOT and idle, two conditions in which the
>computer is in open loop and doesn't receive O2 sensor input.

>When I got the car it didn't have an air filter (a dubious "performance
>enhancement" by the previous owner), so I installed one right away.  Could
>it be that the air metering plate is sticking open occasionally at idle from
>gunk buildup and causing the rich condition?  Any BTDTs would be most
>helpful.

>Thanks all,

>Matt
>'86 4kq
>Chapel Hill, NC