I was having trouble getting my '89 240SX through emissions testing. I'd tried the usual suspects (PCV valve, air filter, even plugs and wires) and it went from failing CO only to CO & hydrocarbons.
Despite the ECU not showing any errors, I tried to replace the O2 sensor with an old one I'd removed (that I think was ok). Now, it won't even idle. If I try to let it idle or try to keep it at a constant RPM with the throttle, it wants to die. Disconnecting the O2 sensor altogether seems to help a little. Putting the other O2 sensor back in didn't change anything.
The ECU shows a code of 12 (air flow meter circuit) now. But, I don't know if I should trust it. The O2 sensor connector seems frayed.
Could I have accidentally disconnected some hidden sensor, or should I just buy a new O2 sensor now?
Thanks