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89 Ford Festiva NO emmissions prolem only at 25 mph

Emmissions test shows: very low HC, zero CO, 700 of allowed 900 NO at 15 mph, 860 of 600 allowed NO at 25 mph. New catalytic converter, carburator tested and shown to be providing correct mixture. Suggested, pinhole somewhere between exhaust manifold an converter, carburator running too lean for no apparent reason (there are no bullitins on this problem, carburator is rebuilt recently, computer and testing shows it's leannest stuff to be operating correctly), or engine needs to be tested only in morning, possibly with fan blowing on it, to be cooler (suggested by bureau or automitive repairs, seems unlikely since it does not onverheat or anything).

Posted by Anonymous on


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Posted on Jan 02, 2017

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Hello what you need to do is throw a fresh set off plugs in the motor go to your parts store ask to buy a bottle off emmission pass follow the instructions you should be okay goodluck please rate

Posted on Oct 02, 2008

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SOURCE: emission test 25/25 hc ppm read 00170 allowed

  • There are a couple things here that could be the issue. One would be your Catalytic Converter. The other would be your 02 sensors. It is possible you are running just a little bit rich. There is a sensor on the exhaust not far off the manifold (this is called the upstream sensor). There is another 02 sensor down the exhaust a bit by the Converter (this is called the downstream sensor.

  • Most of the time you will know when the 02 sensor is bad because your fuel mileage will go way down. Often times a check engine light will come on as well (but not always). A failure 02 sensor will run a vehicle rich and that left over fuel from combustion can cause pollution and a failure of an emissions test. However, if you are not loosing any fuel mileage, and you don't have a check engine light on I would be inclined to think that the converter has passed it's point of functionality and needs to be replaced.

Regards, Tony

Posted on Apr 29, 2011

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SOURCE: When the engine idles the


Posted on Jun 03, 2011

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SOURCE: passed 25 mph emission test

When was your last tune up? I mean new plugs wires and distributer cap. have you had the throttle body cleaned if not that will need to be done as well. The cleaning is not hard or expensive but it cleans all the build up off the throttle body. Catylytic converter may also be plugged. What I would do before your test is to run the car, get it good and hot and run it down the highway while holding the gas pedal to the floor several times to get the old carbon burnt out of the exhaust system, this old carbon in the system can cause high PPM readings for the hydrocarbons. Which simply means your engine is either not getting hot enough to keep the build up cleaned out, or your not burning fuel effeciantly causing a build up. If your getting no trouble codes or lights then the chances of an electrical system malfunction are minimal. There is also the possiblity that your engine needs some valve work done if the fuel is not getting burnt properly but if you get it good and hot and run all the old carbon out of the system you have a good chance at passing the test.

Posted on Sep 15, 2011

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SOURCE: I failed emission on my

Hello! could you clarify one point for me before I offer a solution...Have you dropped in a different engine? The largest V6 in 1990 was a 3.3L...Perhaps it is just a typo but the 3.8L was not an option until 1994...You have it as a 3.9L...It's important in order to answer correctly...Send a comment...I am working on the fault which appears to be a missing air pump belt...Saailer

Posted on Sep 22, 2011

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