Goes full throttle as soon as it starts...

There are two coolant lines that connect to this Honda IAC to help quiet the operation of the valve. The part number for a OBDI 1992-1995 Honda Civic Idle Air Controller is 36450-P28-A01. While the OBDII version of this valve is 36450-P2J-J01, and the two units are very similar in design and execution. The EACV or Electronic Air Control Valve is a big part of maintaining your Honda Civic idle. If you've checked your IAC and your Honda still suffers from a surging idle, check your FITV. This Honda Idle Air Controller or IAC is under the throttle body and incorporates into the throttle body passages o locate your Fast Idle Thermo Valve, remove the intake snorkel and locate the FITV beneath your throttle body opening. If your SOHC engine is still having problems, check our guides above on how to check your FITV as well as your IAC. To check this operation, remove your air intake pipe and use your fingers to plug the passages in the lower left hand corner of your throttle body opening. If your idle surge does not go away, unplug your Idle Air Control valve and if that stops your idle surge, your IACV must be replaced. Follow our instructions on how to replace your Honda Civic Idle Air Control Valve. Need to raise your Honda Civic idle or having problems maintaining idle? You can adjust the base idle by unscrewing or screwing in the Idle screw on your throttle body. This screw allows air to bleed into the passages on the backside of your throttle body, as shown above. To learn how to adjust Honda Civic idle speed, you will not need to remove anything. With a standard screwdriver, simply locate your throttle body and Idle screw.

First is all always write down the codes you have present, it helps in closing down on the problem. I am assuming you have a 95 Mazda Milleinia

1. Start and run the engine and monitor the oxygen sensor signals and see if this sensor has bad readings still. Check for an open or shorted wire between the sensor and the Engine Control Module (ECM) if the signal is dropping out.

2. Listen for an exhaust leak in the area of the oxygen sensor, the leak could allow oxygen in to the exhaust and skew the sensor readings.

3. Inspect the ECM and ECM connector for signs of something that has been spilled on the ECM. Is the engine idling too high or too low then check this:-
1. Unplug the idle air control valve and turn the air bypass screw in to see if it will idle down. If it will idle down, adjust the idle speed to around 500 RPM's and then plug the idle air control valve back in.

2. If it still idles high, remove the air boot from the throttle body, block the air bypass ports with duct tape, hook the air boot back on and start it. This should make it not idle at all or just barley idle. If it does, the problem is in the idle air control valve.

3. If blocking the air ports doesn't cause it to idle down, the throttle plate must be sticking open. Clean the throttle plate really good and back the throttle stop screw off and then see if it idles down.

4. Verify the coolant level is not low and that coolant is circulating through the idle air control valve. Tech Tips: This idle air control valve is two valves in one. It is a fast idle thermo valve on one side and a duty cycle idle air control valve on the other.

I’m happy to assist further over the phone at https://www.6ya.com/expert/uttamjeet_2f3adc18600f8ede

Lots of great suggestions have been made by other contributors. I just have to go with my own experience and have you check that your electric cooling fan is kicking on. I lived in a hot climate, driving in city traffic, and the brushes in that motor wore out after just a couple of years and kept the car from performing properly at idle due to an overheating engine. Most of my mysterious engine problems went away once the engine compartment was cooling properly again.

If you can keep giving it gas and it runs above idle with no problem, then you have a blocked or bad idle control valve on the throttle body assembly. With your foot off the gas pedal, the large throttle plate inside the throttle assembly is closed, but some air is let in through the idle control valve or motor through a separate passage. This can get clogged with deposits over time and poor idle results. The valve is controlled by the engine computer. It is how the computer controls idle speed- more air if the idle control valve is opened wider, higher idle speed.

"...like its not getting any gas..." Oh yeah, it's getting gas, the injectors are still pumping gas into the cylinders, but it may not be getting any air. All the accelerator pedal does is control the air supply into the engine through the throttle body. So modern cars have an air pedal, not a gas pedal. Then the computer takes over and matches the correct amount of gas through the injectors to the known supply of air in the intake manifold. Neat system, eh? Sorry if I sound so pedantic, dale. check your idle control valve.

Could be a dirty or stuck throttle plate, faulty idle air control valve, or a large vac leak.
The computer controls the idle speed by regulating the amount of air entering the throttle body thru the control valve.

Usually a sign of a faulty idle air control valve, a sticky throttle plate, or a vac leak.
The computer uses the control valve on the throttle body to control idle speed by regulating how much air enters the throttle body and intake.

dirty or bad idle air control valve i would at worst the egr valve but most likely the idle air control valve which controls the air and idle from the throttle body try taking it out and cleaning the tip as well as in the throttle body where the control valve goes in if that dosent work replace it and the check engine light does not have to be on for it to be bad.good luck to you.


10 year ford tech here.

Sounds like you idle air control valve is starting to mess up. You can actually take this off and clean it with throttle body cleaner and it should help get your idle back to normal. As is sounds the idle air control valve controls how fast/slow your car idles. It is located on the throttle body normally held on with a couple of screws. The throttle body is where the air duct hose coming from the air filter box ends at the engine block. Here is a picture of what you are looking for:
Make sure that you clean the valve portion and not the electrical plug with the throttle body cleaner. Let it air dry or blow lightly with compressed air before putting it back on. Let me know if you have any more questions. Thanks for using FixYa!

the idle air control valve is stuck,or there is a vacuum leak.check the vacuum lines,the throttle cable is not sticking and the idle control valve which is on the side of the throttle body and the throttle position sensor.check all the plugs on these for a good connection.

Idle air control at base of throttle body. Passages could be plugged or idle hard stop needs adjusting.

Air Intake System Sensors Air intake system sensors include a heated resistor-type mass air flow (MAF) sensor and throttle position (TP) sensor; both supply data to the powertrain control module (PCM). The PCM also monitors engine speed.
Air Intake System Control Devices The idle air control (IAC) solenoid regulates idle speed by adjusting the amount of air allowed into the intake manifold. Adjustment is made by varying the duty cycle output by the powertrain control module (PCM). The PCM will increase the duty cycle for added mechanical or electrical loads. The IAC solenoid is combined with the fast idle control (FIC) solenoid which is turned on when the air conditioner is engaged to help compensate for the additional load. The IAC valve must be replaced as an assembly with the FIC solenoid.
Fast Idle Control (FIC) Solenoid The fast idle control (FIC) solenoid (Figure 1) compensates for idle speed change caused by the operation of the air conditioner compressor. The FIC solenoid is controlled by the FIC relay. The FIC relay is energized when the air conditioner clutch is energized and the relay allows the FIC solenoid to turn on and let an additional volume of air into the intake manifold.
Figure 1: Fast Idle Control (FIC) Solenoid

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Throttle Body (TB) The throttle body (TB) controls the amount of air that flows into the engine through a single butterfly valve. The single butterfly valve opening is determined by the accelerator pedal. The TB is cast with an air bypass channel and houses several emission-related components for the powertrain control module (PCM).
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Throttle Position Sensor (TP Sensor) The throttle position (TP) sensor responds to the accelerator pedal movement. The TP sensor is a potentiometer that transforms the throttle plate opening angle into output voltage and sends the voltage signal to the powertrain control module (PCM). In addition, the sensor detects the opening and closing speed of the throttle plate and sends the voltage signal to the PCM. Also, the TP sensor is used to determine the air intake when the mass air flow (MAF) sensor fails. This mode of operation is called Fail Safe.
The TP sensor integrates the idle (IDL) switch within the housing. The IDL switch detects when the throttle plate is closed and an idle condition occurs. The PCM is supplied with this input signal.

IDLE SPEED