Hi,
That's an interesting one. Usually the opposite happens. Because this can be the results of several different things, what I suggest doing is scanning the computer. By doing this, we will know what diagnostic trouble codes are stored in the computer. These codes should point us in the direction of what components are causing the issue. Here is a quick video showing how it is done:
https://youtu.be/YV3TRZwer8k
Now, I realize most people don't own a scanner. However, most parts stores will scan it for you free of charge or lend/rent you a scanner.
Here is the issue with scanning this vehicle: You are right on the border of a change in protocol. This year is when some vehicles were changing over from OBD1 to OBD2 diagnostics. Most 1995 vehicles have OBD2; however, I just checked the manufacturer's code list and it appears to provide OBD1 codes.
If you take it to a parts store, they will be able to identify the connector you have and determine which it is. If they tell you it is an OBD1 type and they can't help, here is a link that shows how to do it at home without a scanner.
https://www.2carpros.com/articles/diagnostic-trouble-codes-for-1995-and-earlier-mazda-cars-obd1
If I had to guess, I would say it is the newer style.
Next, the idle speed is controlled by an idle air control valve (IAC) or on your vehicle it's known as a bypass air control (BAC) valve. This valve could be dirty or not reacting properly all the time. So, here are the directions for testing it. The attached pics correlate with these directions. Note these are for the 2.0L engine. If you have the 2.4, let me know. You indicated it is a 7.6L. That is over 460 cubic inch. I don't even think they make engines that big any more. LOL If they do, you have one fast 626.
Note: The IAC is located on the throttle body. If you look at pic 4, I circled the part you are looking for. If you do decide to remove it for service, make sure it is clean and nothing is blocked by carbon.
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1995 Mazda 626 L4-1991cc 2.0L DOHC
Automatic Trans.
Vehicle Powertrain Management Fuel Delivery and Air Induction Idle Speed/Throttle Actuator - Electronic Testing and Inspection Component Tests and General Diagnostics Automatic Trans.
AUTOMATIC TRANS.
COMPONENT INSPECTION
BAC/Air Valve
1. Remove the BAC valve.
2. Cool the BAC valve to below 0°C (32°F).
pic 1
3. Heat the BAC valve at point A by using a blow drier, and verify that part B moves in the direction of the arrow in the figure.
4. If not as specified, replace the BAC valve.
BAC/Idle Air Control Valve
Pic 2
1. Disconnect the idle air control valve connector.
pic 3
2. Measure resistance of the valve.
Resistance: 7.7-9.3 Ohm (at 23°C 73°F )
3. If not as specified, replace the BAC valve.
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Also, here is a link that explains how to service an IAC. You may want to remove and service it.
https://www.2carpros.com/articles/idle-air-control-valve-service
Here are links you may find helpful when testing the electronics of the IAC.
https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester
https://www.2carpros.com/articles/how-to-use-a-voltmeter
https://www.2carpros.com/articles/how-to-check-wiring
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Do this and let me know what you find. Also, this should be done when the check engine light is on. If you have additional questions, let me know.
One last thought, the conditions you are experiencing (minus the light) can be a few different things. Things such as engine vacuum leaks, a failing idle air control valve, low fuel pressure, and so on and all cause these types of conditions. That is why I'm suggesting the test. Otherwise, it becomes a guessing game and will require testing several different components to narrow things down. I hope that makes sense.
Your
Let me know what you find.
Take care,
Joe
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Friday, February 28th, 2020 AT 8:31 PM
