This car has about 144,000 miles, and I have had no problems until now. I have had the Idle control valve replaced before. About 2 weeks ago, my check engine light came on.
The car was running rough, shaking, and idleing below 500 RPM. I had it checked and the codes showed that O2 sensors Upstream/downstream were to lean.
Replaced all 4, car ran ok for a few hours check engine light came back on. The car now idles up high then back down like it is about to go dead, but does not fall dead. Ran another check and it stills says it is the 02 sensors running lean.
I have not noticed any hissing for air/vacum leaks.
What could cause the test to show 02 sensors running lean after they have been replaced?
Need help...............
