1986 22R-E Rough Idle

Rough idle on 22R-E engine. Runs beautifully on the road but loads up upon stopping and seems to run rich at idle and stalls. "Check Engine" light comes on and goes out when at idle or coasting. Does anyone have any idea where I should start looking. Appreciate any help you can give me.
Thanks

ps..The last thing done to it was a new exhaust manifold a few months ago but it is a camper and has not been driven since. I'm thinking oxygen sensor might have been disturbed and is not functioning properly. I know little about this vehicle because it always ran like a top and I don't even know where the connection is to read the engine codes with a voltmeter. Appreciate an opinion and info, where the conector is, what terminals to read, and the O2 code. Wife going to be very upset if I don't get this thing going for weekend tailgate party.

Thanks again for any advice

I've never had to deal with an o2 sensor, so I can't help you there. But I would start looking in the fuel delivery (i.e. fuel filter, pump, injectors...)