Just failed emissions test at the local Firestone here in Texas. All reading except NOx ok High Speed results standard reading at nox848/893 my reading Low speed test standard nox937/1157 my reading. The following was there recommended services oxygen sensor $395.50 install 27.60 engine idle air control motor 289.80 install 82.80!!! and new catalytic converter 434.00(cats about 2 year old)Total bill was for 1,329.21....

I think they trying to make a boat payment off me! Ordered new O2 sensor for 120.00 and may buy idle air control. Any thoughts?

Thanks
Scott

I had the same thing happen to me last year (you can look up my posts on that if you wish). there is a very high probability that you will need a new cat. the O2 sensor is a lower probability. make sure you have new spark plugs, dist cap and rotor, an the vacuum reading are where they should be (no vacuum leaks)

Order your own parts and install yourself.

You may very well need a cat and an O2 sensor but the IAC will have no effect on getting your vehicle through smog. You may have other problems that the IAC will address but from the sounds of things you are doing a "loaded mode" test and the vehicles idle quality should not even come into the picture. Any idea how good of a cat you had installed last time. You typically get what you pay for in catalytic converters and some times you do not even get that. I can get cats done anywhere from about 75 bucks on up and the $75.00 variety is what we in the business refer to as the "clean for a day" model. If you had a bottom of the line cat installed two years ago it would be entirely possible for it to be dead today. Elevated NOx is caused by excessive combustion chamber temperatures. Typical causes of this are lean air/fuel mix or overly advanced or severly retarded timing. Make sure that your fuel filter is clean, you have no vacuum leaks, and that the O2 sensor is working properly. Obviously the easiest way to do this is to hang new parts where you can. Make sure that your vehicle is good and hot when you deliver it to the shop to have the smog test done again and put some good gas in it, not the 87 octane that we all run.

Mark

Thank for your response. The idle seems to be steady on the car. The cat was replace by the local indy with oem it seem to run me around $350+ and still on warranty I believe. After I get the O2 sensor I'll have the indy check out the cat.

Thanks
Scott