The same code combination in my 90 along with a code that indicated Bad or Missing Idle switch ground allowed me to pick up a great vehicle cheap after the previous owner had stuck over $1600 into the vehicle and it still could not pass emissions. My good luck should save you some $$$.

The one item that all the codes in the vehicle had in common is the ground for the computer.

Injectors need a good ground to pulse according to the computers signal. How does the computer know the injectors are not firing properly? The only thing that can be measured is the current drawn by the injector as it fires. Ohms Law applied. If resistance is up or down, more or less current is drawn, computer thinks injectors are bad.

If the O2 sensor is compensating for a rich or lean mixture, what is causing the mixture to go lean or rich? A poor ground increases or decreases resistance for the injector so it opens for a longer or shorter period, resulting in a rich or lean mixture. O2 sensor compensates, computer issues code for problem.

How does the computer know the idle switch is not grounding? It can only compare it to another ground, which happens to be via an internal route, which alos hapeens to be the ground for every other ground the computer needs. Since the switch on my vehicle checked as 0 ohms to ground with the switch disconnected, the only item commmon to all three was bad computer ground.

What I did was:

Removed, cleaned and reattached the two ground points for the computer on the manifold.

With battery disconnected, removed the connector to the computer and the computer from the auto and sprayed the connectors with electrical contact cleaner, air blasted dry, reinstalled and reconnected.

Removed and cleaned the grounding "loops" near the computer connection.

During that same disconnected battery time, removed and cleaned the battery negative to block connection and the ground strap bewteen the Valve cover and body at the right rear of the engine.

Have not seen an engine code or light since.