QuestionQUESTION: My 1992 Miata will die when the a/c compressor kicks in. It idles fine when the compressor is off. I tried spraying carb cleaner into the Idle Control Unit as described in another answer but that did not help.
Thanks in advance.
ANSWER: No the problem is actually electrical. The Idle Control Solenoid (ICS) has likely failed. It happens to them all at some point. The down side is they are near impossible to located in good used condition and there is no guarantee of long term success with a used one if you find one. New is quite expensive and Mazda is the only source. Good news though if you make the jump and buy a new one it will probably not fail on you again or at least for another 16 years.
The device is the computers mechanical connection to control throttle upon demand at idle. As the AC, PS or Alternator come on line and place a load upon the engine this device compensates for the idle air and stabilizes the idle speed. It also works in conjunction with the air valve, they use coolant as a temperature signal during warm up.
At idle you should notice a slight turn of the steering or turning on of the headlights or blower to cause a mild fluctuation in the RPM's. It should flutter down then recover almost instantly if the ICS is working. The AC being the biggest power hog draws as much as 10 Hp from the engine so it of course makes the biggest change in the RPM. If the idle drops and does not recover the the ICS is the fault. To confirm the device has failed shut the motor off, leave the key on. Locate the ICS harness plug and disconnect it (it's tough to access, below the the throttle body) when unplugged and re-plugged it with click if the solenoid is operating, No click, no solenoid = bad ICS. If it clicks the plunger may be stuck however, in my experience it is a lesson in futility to clean them and expect it to return to normal use in a car that has seen daily use. Only in a car that my have been set up for some time 6 months+ might actually benefit from cleaning. The root cause is internal in your case and will most likely require replacement to resolve.
service@miatashop.com
"If your good at what you do, you should be well paid"
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QUESTION: Thanks for your quick answer. Until I can get the ICS am I doing any damage by just keeping a bit of accelerator pressure to keep the engine from dying at a stop?
Thanks again.
AnswerNo not at all. Your doing the job of the ICS. No ill effects can come from a failed ICS just the inconvenience of having to idle up your self. If it becomes a problem for you you can advance the idle stop screw to increase the base idle which might aid it from killing when the AC is on but, the flip side is the base idle speed will be higher.
