o2 downstream problem

06-19-2012, 10:46 PM
I had a surging problem when cold at 25-35 mph. replaced both o2 sensors with bosch. Problem went away. Now have check engine light. code says downstream o2. replaced o2 downstream with another bosch, same problem. I think the stock o2 was a denso. any suggestions? Thank you.

06-20-2012, 11:55 AM
Incoming Air -> MAF sensor -> Engine -> H02 sensor for a feedback signal.

Did you clean the MAF sensor with CRC MAF sensor cleaner?

06-20-2012, 12:25 PM
Thank you!

I will clean it.


06-20-2012, 10:16 PM
I cleaned the MAF 35k ago. the car has 83k. After I put a new filter in, I will let you know if the light goes out. Does the orientation of the MAF matter?

06-21-2012, 09:25 AM
cleaning maf might remedy a lean code if the maf element was dirty or contaminated but a 02 code.........what code are you getting?what size engine?

06-22-2012, 01:27 PM
I cleaned the MAF and replaced the air filter for the engine. I haven't driven it, so I will let you know if the light goes out. I did not write down the failure code. When I go back to the mechanic I will ask him for it. I do have a leak at the throttle body. The engine size, 3.5

Thank you.


06-22-2012, 09:16 PM
you will need to replace throttle body gasket....this will cause a lean condition

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