o2 downstream problem

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.

Incoming Air -> MAF sensor -> Engine -> H02 sensor for a feedback signal.

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

Thank you!

I will clean it.

Tim

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?

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?

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.

Tim

you will need to replace throttle body gasket....this will cause a lean condition