High CO at emissions test
Computer controls engine idle thru a idle air control valve, air control valve could be dirty or bad, recomend to clean valve and clean throttle body bore with cleaner and see if idle inproves
The simple answer is you don't, short of reprogramming the ECM. Follow Ron's suggestion to improve idle. However, this will have little effect on CO emisions - a complex problem Probable causes are bad catalytic converter, bad O2 sensors, EVAP system malfunctioning, poor manifold vacuum, etc etc etc.
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SOURCE: ASM 2525 NO ppm TAILPIPE EMISSIONS failure
have you had the the engine codes pulled and reset?
and if so what are your engine codes?
i dont know of any car that will pass emissions test with the engine light on.
we cure your trouble that caused your engine light to come on and you will pass your test.
later
paul
SOURCE: Emission test failed.
daves944 is dead right . you could try thrashing the ars of it just befor it go in again most mot places will do it for you if you ask them ,, but be warned if it go bang witch it should not its not ther fault,,,, it has worked for me more then once
SOURCE: High idle speed when the engine is cold
The high idle speed at start up is normal. As the engine temperature increases, the engine idle should kick down automatically. Insofar as the emissions results, if there were a problem, the check engine light should be on. If it is, take the car to an autoparts store and have the fault codes read. Most parts stores will perform the scan for free. If the check engine light is not on, and the idle question was all you were worried about, you are good to go! Hope this helped and best wishes.
SOURCE: My 1991 4runner failed emissions test with high CO and HC levels.
Not sure, but did you replace the oxygen sensors. Is your catalytic converter still good?
SOURCE: 1991 Honda Accord LX failed emission test on smog
not enough info. Typically, CO and HC together can be the result of poor fuel control or misfire, or worn components such as O2 sensor or catalytic converter, but without more data, repair recommendations are likely to waste money and not achieve success.
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