1992 Mazda 323 engine idle

Tiny
COCKATOO18
  • MEMBER
  • 1992 MAZDA 323
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 235,000 MILES
Hello,
My Mazda Astina has an engine idling problem. This problem happened over a period of time not at once. It began when driving the car and stopping at lights etc the idle would go up from around 750rpm up to 1200 -1500rpm then it would drop back to normal[750rpm]. Now it sits permanently on around 1200 rpm at idle after warming up.
The car has been to several mechanics using diagnostic equipment and no one has been able to diagnose the problem, not even a Mazda dealership.
I've replaced the airflow meter, the idle adjuster[sits on LHS side of throttle body]and the water temperature control valve[sits underneath LHS of throttle body]. All the wiring has been checked for earthing problems.
Could it be the ecu causing the problem?
Hoping you can help
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Thursday, November 13th, 2008 AT 4:39 AM

4 Replies

Tiny
RASMATAZ
  • MEMBER
Check the idle speed control valve and throttle position sensor and throttle plate
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Thursday, November 13th, 2008 AT 4:48 AM
Tiny
COCKATOO18
  • MEMBER
Thanks razmataz,
That is a very quick reply.I've had this idle air control valve checked out[replaced]. Is it still possible it's the ecu?
If you can solve this b** idling problem I'll definately give a good donation as no one has fixed this problem yet.

Thanks cockatoo18
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Thursday, November 13th, 2008 AT 5:21 AM
Tiny
RASMATAZ
  • MEMBER
Could be the PCM not targeting the idle speed

If a vehicle idles erratically and surges (idle speed is not steady and increases and decreases), the problem may be a buildup of carbon or fuel varnish deposits in the idle speed control valve (also called the idle air control valve or IAC valve). The cure for this condition is to clean the valve with some aerosol throttle cleaner or engine top cleaner.

Here's how to clean the IAC valve:

Disconnect the air intake ductwork from the throttle body.

Start the engine, then increase and hold the idle speed to 1,000 to 1,500 rpm.

Spray the throttle cleaner or engine cleaner into the throat of the throttle body, aiming for the idle air bypass port (usually located on the side or top of the throttle body opening). Give this area a good dose of cleaner (about 10 second's worth).

Turn the engine off to allow the cleaner to soak into the IAC passageway.

Wait about three minutes.

Restart the engine, rev and hold at 1,000 to 1,500 rpm, and repeat the cleaning process again.

Turn the engine off again, and reattach the air intake ductwork to the throttle body.

Start the engine and rev and hold to 1,500 to 2,000 rpm until no white smoke is coming out of the exhaust pipe.

If this fails to make any difference, you can remove the IAC valve from the throttle body and spray cleaner directly on the tip of the valve and/or into the ports in the throttle body. Let the cleaner soak awhile, repeat as needed, then reinstall the IAC valve, start the engine and run it at 1,500 to 2,000 rpm as before until no white smoke is seen in the exahust.

If the idle speed still surges after this, the IAC valve is defective and needs to be replaced.

Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor/valve stuck in the extended (high idle speed) position/throttle position sensor. Also the throttle plate could be binding in its bore and kinked accelerator cable, coolant temperature sensor might not be operating properly misleading the computer that the engine is still cold and computer throwing fuel at it raising the idle speed.
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Thursday, November 13th, 2008 AT 5:29 AM
Tiny
COCKATOO18
  • MEMBER
I'll diassemble and give it a try. Get back to you later. The idle is steady and not erratic.
Thanks,
Cockatoo18
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Thursday, November 13th, 2008 AT 5:36 AM

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