QuestionThe problem of not idling (but will run fine when driving down the road )all
started after the fuel injectors were cleaned. Is it possible that one of the fuel
injectors went bad? Or could it have gotten stopped up with trash that was
flushed?
AnswerThe symptoms you describe could be as simple as ignition break down (ie; a bad wire(s) or a spark plug(s)) It could also be a stuck or non functioning air valve or gum/varnish build up in the throttle body. Mis-adjustment of base timing and idle could also be to blame.
Start simple. As most issues with early Miatas are simple and revolve around common preventative maintenance items.
Check for fire on 1&4 and then 2&3 use a positive grounding test plug since a CDI system like the Miata needs to find a good ground to avoid primary winding overload. A lack of fire on any pair indicates a coil or a crank angle sensor signal, lack of fire on a single lead is a primary wire issue.
If you haven't in awhile get a new set of NGK wires and spark plugs as a first step. See if that resolves your issue, 90% of the time it does. Then move to clean the throttle body, ICS (idle control solenoid) and the PCV while your at it.
The next logical step would be to check the air valve for movement over it's temperature range. If you have let the coolant go and corrosion is present in the system this could be a good indicator that the air valve (a thermostatic device) similar to a thermostat in operation could be stuck or non-operable. It is a cold start device that adjusts bypass air during warm up (a choke of sorts). This is a worst case item so try the basic preventative items first.
Fuel injectors are seldom an issue.
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