93 850 Failed Smog

03-10-2004, 07:46 PM
Recently i had a valve job done on it. They resurfaced the upper head as well. After getting everything back together, It ran. The engine light was still on, but i figured it was because i never reset it. About 800-1000 miles later I checked the codes and recieved "missing or bad o2, missing or bad MAF". I reset the ecu (A2) and drove it around, then cheked for faults in A2. I found none. When I took it in for smog I failed Hydrocarbon(max=85 meas=102) at 15mph, but passed at 25mph. I've read that O2 sensors can go bad and be undetected by the ecu. It has seemed to lose power on acceleration, but i thought maybe 'cause it had 140k mi on the engine. Should i try to clean the MAF and O2 sensors? How can I be sure they're in working order? What else should I look for?

03-11-2004, 06:27 AM
If you car is turbocharged you probably fuxored the MAF and O2 sensors that happened on a T5 i had and it costs a bit too much to get it repaired. Best to just swap the sensors yourself. If that doesn't work.........

03-11-2004, 03:20 PM
does the O2 sensor on the exhaust before the cat need special wiring? My local Kragen has two types. One with wires and one without. Are the two sensors identical? And do I need to specify which one i need?

03-11-2004, 07:40 PM
Okay here it goes. The front O2 sensor does it's job by notifying the ecu that either the exhaust is too rich or too lean correct? The exhaust continues on to the cat and assuming everything goes according to plan the final product is cleaner air. If the O2 sensor however does NOT pick up the fact that the air is rich/lean then the ecu makes no adjustments and the cat works even harder and ultimitley fails. Am I on the right track? Now since I'm not getting an indication from the ecu that there is indeed a problem with the O2 sensor, would it be safe to assume that the sensor MAY be "stuck" in an open state indicating that all's well and that there is most probably a failure within the cat as well.

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