I need help! I have a 1991 Mazda 626

Asked by Jul 25, 2012 at 09:37 PM about the 1991 Mazda 626 DX

Question type: Maintenance & Repair

I need help! I have a 1991 Mazda 626
It has a high idle when it gets warmed up. It runs perfect until then.
You can smell gas. But it runs good on the highway. I took it for an emission
Test and it failed. They said the fuel/air mixture was to rich and it was not
burning off all of the gas.

I changed the 02 sensor. The Mass Air Meter/Sensor, the temperature sensor(by the thermostat)
And I changed the idle control sensor.
It seems to have more power when it is cold but when it heats up it is idling high(2000-2500).
It gets sluggish and loses power.

Does anyone know what this could be or should I call the junk yard to come get it?

1 Answer


Sounds like you did all the typical fixes for the problem you are having. A high idle can mean a vacuum leak. A vacuum leak can also cause the engine to burn rich. This simple test might reveal the source of a vacuum leak. With the engine idling take a can of starter fluid and spray around any suspect places of vacuum leak on the engine. If you find a spot where you get an increase in RPM you found the leak. If this doesn't reveal anything try the following vacuum diagnostic. Here is a good reference for vacuum trouble shooting.......... You should get between 17-22 in. hg. depending on your elevation above 2000 feet MSL or mean sea level. To perform this test hook vacuum gauge directly to manifold vacuum. 1. Low steady needle usually indicates leaky intake, a leaky vacuum hose, late timing, or incorrect camshaft timing. 2. If reading is 3-8 inches low and fluctuates at that low reading suspect an intake manifold gasket leak at intake port or faulty injector. 3. If the needle has regular drops of about 2-4 in hg. at a steady rate the valves are probably leaking. (Perform a compression check). 4. An irregular drop or down flick of the needle can be caused by a sticking valve or an ignition misfire. 5. A rapid vibration of about four in hg. indicates worn valve guides. 6. Slight fluctuation of one inch or so indicates ignition problems. 7. Large fluctuation perform a compression check. 8. If needle moves slowly through a wide range check for PCV issues. Hope this gives you a good place to start and helps you figure it out.

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