1990 L98 83k

Okay first off, I have had the local shop replace the EGR valve and solenoid after the engine light came on. Probably has been a few months since then and now I have noticed the car randomly idle heavy and sort of feel like it is missing when I am at low rpm (cruising at 35 or so). The plugs and wires have been changed and distrubitor cap. And today I went and drove it around a bit then I went to go give it a bath. While starting it up from 200 degrees it again idled heavy and was lagging/jumping on the way home (city driving). That was the worse I have seen it yet. I let it cool down and then I started it up again and it idled fine at 900rpm or so. I have also replaced the thermastat and coolant. I have been running 89 octane fuel with 10% ethanol, or should I be putting in 91-93?

I also have set a code at cruise speed telling me that the oxygen senser is "rich"

Maybe they are related but it has been idling rough before the code came on.

 

Sounds like retarded ignition timing. Check that first, be sure and unplug the set timing connector. Brown wire with a black tracer near distributor, one wire connector. Unplug it set timing, then plug it in and clear codes.

 

Does the wire connect to the black box thats attached to the distrubitor? I believe there are 4 wires (each with a clip) that connect to it, onesays tach. I am having a bit of trouble locating the brown wire. And what do you mean by timing it, afterwards?

 

The connector breaks out of the wire loom near the distributor. Unplug it, then set your ignition timing.