I'm going from memory here on locations etc., my '91 has been out of the fleet since ~'96 so if it doesn't seem right, question it.

Start by checking the ignition wires, plugs, and distributor cap & rotor, if any are suspect then replace. Might as well get the maintenance items out of the way.

It's important to define the cold starting issue. Starting when it's very cold out and only shut down for 10-20minutes, starting in moderatly cold (garage or mid-day upper 30s) and the engine hasn't been run for an hour or more (engine at outside temp), etc.

Then when it starts, does it seem to miss for a little while before all cylinders are on-line or pretty much go right to a smooth idle.

I believe that you should hear the fuel pump run (under the car near the rear wheels) a soon as you turn to position 2. It will time-out if there is no ignition signal after a few seconds. If you don't hear it run, the problem is likely a relay and simple to fix.

The cold-start valve (or 7th injector) is supposed to inject fuel to start the engine cold, this is the CIS-E equivalent to a choke. Without it you will have a rough time starting it cold. It requires the coolant temperature sensor to tell it the engine's cold, be sure all sensors are plugged in, and follow the fuel line to the injector on the intake, be sure the electrical connector is plugged in (cold-start injector). Cold enrichment also relies on the coolant-temperature sensor.

Vacuum leaks are a good thing to chase down, I always used small shots of starting fluid to see if the engine revs when I spray to look for leaks. Explosive/flammable, don't spray anywhere it could ignite. Seems that the economy gauge wouldn't be pegged at idle, shouldn't be that much vacuum, but I don't remember where it was on my car so hopefully someone else can tell you if that's normal. If it seems to be running rich, open a vacuum line between the engine and airflow-sensor to see if it runs better, which would support your suspicion that it is running rich. If it runs worse, that indicates it was already running lean. Most cold-start problems are lean.

Leak-down is the CIS's enemy. To combat the possibility of fuel boiling in the hot injectors, there is an accumulator near the pump (looks like a filter) to maintain fuel pressure (~4bar if I remember correctly) for about 20minutes after shutting down the car. If it doesn't work, you'll sometimes end up with no gasoline in injectors after shutting down hot because of the boiling point of gasoline at atmospheric pressure, this will lead to hard starts.
This system also causes complications: if the accumulator and check valve do work properly by maintaining fuel system pressure, and you have a leaky injector(s), the fuel will seep through that leaky injector and into its cylinder. This will have the effect of starting hard, with the leaky cylinder misfiring due to the initial lack of fuel pressure and excessive fuel in the cylinder. This is additionally undesirable because the leaky one will cause some washing of oil from the cylinder wall and additional wear could result.

The injectors in the 103 are held in place by O-rings. These O-rings become hard and shrunken after enough years, and should be replaced. While shrunken, they allow un-metered air to flow past them and lead to a lean idle and part-throttle hesitation. Wiggle the injectors and see if they feel loose. They pull straight out and the O-rings are cheap. They do not seal compression like your 617s, just vacuum.

The fuel system on this car runs at a pretty meager pressure, around 1000psi less than you're used to, closer to household water pressure so they are much less sensitive to disassembly/assembly of fuel lines. Also, it does not have the timing issues of a diesel, it flows all of the time, and fuel will quickly replace air in the system for self-priming.

One thing that you'll want to check is the fuel metering plate. In your system, your fuel is metered mechanically by the airflow lifting a plate connected to an arm, which pushes a plunger/metering-pin into the fuel distributor to increase fuel flow. Fuel system pressure/counterpressure on this pin will adjust how rich/lean it runs. You can remove the air filter system and see your airflow meter (no mass-air-sensor). After the engine has been off for about 10minutes, you can lift the meter carefully (key off) and listen for the faint squealing/singing sound that it makes when fuel passes, that will tell you that there is some residual pressure, and the accumulator/check valve/injectors are holding pressure. There is a proper and more precise test, but I've found this to help me in initial diagnoses.

When lifting the metering plate, feel for any dragging or sticking. I've seen a few that wouldn't start in bitter cold, it was just the gunk/oil on the mechanical part of the air-flow sensor that resisted motion. Cranking wouldn't create enough airflow to overcome the resistance so the meter wouldn't move and send fuel. Some fun stories about starting a car by lifting the plate through the adjustment hole with its dipstick, owner amazed, ...

Cleaning the while airflow meter mechanical portion is a good idea but be careful to not bend or force anything. The plate should be centered in the opening, play in the pivot shouldn't let it touch either side. At rest, it should be in the minor-diameter part of the opening, not above or below where air can get around it.

Let me know also what the number is on the fuel computer (behind the plastic splash-shield rearward of the battery), I have a used spare in the shop and don't remember which engine it's from, you're welcome to it.

The thing to remember about CIS is that it is a Constant Injection System, the airflow varies the flow rate through the injectors mechancally via the plate just described, it is a fairly simple system. the CIS-E variant (yours) is different in that it can vary the fuel rate slightly vs the airflow. Checking the flow rates and patterns etc. on the injectors can be done easily with a stopwatch and six graduated cylinders to stick the injectors in.

Hopefully you've already found your problem, if not I hope that this will help you to get started.

__________________

Gone to the dark side

- Jeff