Rough Idle on 1986 GMC Jimmy.

I actually had to replace my EGR valve and the gasket. I clean the valve well and reused both. I don't think the gasket sealed well enough though. So I went ahead and got a new valve, gasket and changed them. It runs a lot smoother now.

Code 37 is torque converter clutch solenoid failure. Transmission wont shift in and out of overdrive.

It could be a fuel problem, but in most cases the rough running would continue at road speed.
You could certainly change the fuel filter and see what happens.
A rough idle but no problems on the road would point to a vac problem or maybe a burnt valve. A fuel or ignition problem would be at most speeds including when you put the engine under a load.
Its possible to have a faulty injector on one cylinder that is bad enough to cause a miss at idle but smooth out on the road, but that is a rare occurance.

bad motor mount..check main mount top passenger side..when in gear the motor side of the mount hits the frame side of the mount..just did mine after wondering why it ran like garbage at stop lights..

mcdevito75 here, Sounds like a faulty voltage regulator, it"s 1 unit with the alternator, change the alternator, also the alt. supplies juice to the ignition switch, distributor abd plugs, thus a rough idle due to bad alternator.

ROUGH IDLING CAN BE CAUSE BY MANY THINGS.I AM LOOKING AT LEAKING VACUUM HOSES OR INTAKE MANIFOLD GASKET LEAK.DIRTY FUEL INJECTORS AND WORN ENGINE VALVES WILL CAUSE ROUGH IDLING.ALSO LOW IDLE SPEED CAUSE ENGINE TO RUN ROUGH.

Sometimes a rough idle like that is a fuel filter. As you've already done the plugs and wires the fuel filter would be my next bet.

Basically clean up before use like opening the plugs and adjusting the spark gaps, spray some carb cleaner at the intake & if The soud of the engine smoothens even slightly, then add some it to the fuel in the fuel filter & gun the engine a few time. Flush the radiator and fill in frsh coolant/water. Check the level of water in the battery and top up with distilled water. Clean the air filter and check fan belt tightness. After these small maintenace checks it should run OK.......sodeep

IDLE POSITION CENSOR IT IS ON THE OUTSIDE ONTHE SIDE OF YOUR TBI DISCONNECT THE WIRING IF THE IDLE SMOOTHS OUT IT IS YOUR PROBLEM IF YOU LEAVE IT UNPLUGED IT WILL RUN FINE BUT YOU WILL HAVE A CHECK ENGINE LIGHT

w/o much more info it sounds like it needs a good tune up plugs wires fuel filter pcv vave throttle bore clean and injecter clean,try to do most of this your self it is costly