I currently have a 1985 corvette, and it has a very rough idle.

When it's cold, it DOES run better, but giving it gas / turning back and forth SEVERELY drops RPMs and sometimes kills the engine if I'm reversing and actively turning the wheel. Seems to be the energy put into the power steering pump / reverse are too much for the current issue plaguing the engine.

I have a snap-on 2500, with the proper cartridge, cables, power cable and have connected it to my diagnostic port, and it works.

There are no active CEL codes.

What should i check/verify, and in what order?
Also, how do I take readings of vacuum pressures, fuel pressures, etc to ensure each stage?

Whats the best way to ensure the opti-spark, plugs, wires, and such aren't the issue?

How can I verify the injectors are fine / not clogged.... use a standard diode / resistance reading on a multimeter and look for +-10% deviation from each?

What about a throttle body adjustment / calibration? MAF / IAC? What about 02 or timing sensors? I have looked at 02 oscillations on my car for diagnosis, and looking for open/closed loop to help diagnose (on my car it ended up being the PCV valve).

The battery reads proper voltage, and it runs fine when at high speed, albeit it can seems to misfire/have bad timing at times, but no issue is detected.

Ideas and procedures I should do and look for to diagnose?

 

This will be moved to the C4 Tech/Performance section.

 

If you have not replaced basic tune up items like plugs, cap, fuel filter, wires, o2 sensor... now might be a good time to do that. 85's have old school distributor - not optispark.
Next, there is a minimum idle reset procedure. I would go through those steps - you can search and find that on the forum.
You can also search the forum for the resistance specs on the injectors.
Moving on, get the required gauge to measure fuel pressure through shraeder valve on the rail. Tape the gauge to the windshield and drive around looking for pressure variations. Also measure pressure hold after shut down. I will bet, if you have original injectors some are leaking.. I will also bet your fuel pulsator in the tank is ruptured - not holding pressure.
Next when the car starts to have issues, unplug the maf and see if things get better. If they do, you might have a bad maf of bad burn off module (unique to 85)
My car had similar issues and it turned out to be the ecm (or so that is what I was told by the stealership back in the day) .
Lots of other ideas, and most of the forum members will tell you to get a factory service manual.

 

You can look at idle timing and IAC duty cycle perhaps… easier said than done.

Also be careful installing the IAC as it seems to be delicate with regard to movement of the valve by other means than the servo.