I have a 2003 Civic Hybrid. The engine light has been on for awhile, so we checked it and it looks like the oxygen sensors (front 2) may have to be replaced. Removed them and re-installed them last night just to check them out (didn't replace them yet). This morning when I started the car, the engine immediately raced, as if the accelerator pedal was pushed to the floor. I immediately shut it down. Then I tried it a couple of more times - same issue. I carefully checked the obvious mechanical linkages, i.e. accelerator cable, cruise control cable). Both move freely and snap back to their starting positions. Then tried starting it and putting it in gear to see if that would jar something loose to get it to idle down - this did not work. Could messing with the O2 sensors have caused this? Could there be an issue inside the throttle body? I'm stumped. Any assistance will be greatly appreciated. Thanks, Charlie

 

Any help, insight, advice would be greatly appreciated! I have the hose from the air filter to the throttle body off and everything inside seems normal. I am really at a loss to think of what would be causing this problem. As soon as the car is started, the engine sprints to about 4.5k/5k rpms and stays there. Even after starting, the throttle does not budge. The accelerator and the cruise control cables are not stuck and they will both open the throttle and snap back. The throttle looks to be in the correct idle position.



The area that I was working on the o2 sensor is pictured below with the throttle cable on the right going in to the firewall and the cruise control cable bending to the left.



What I am having a hard time understanding is why the engine is prompted to immediately race. I cannot see any vacuum hoses that have been dislodged. Could it be a sensor? Would disconnecting the battery maybe have any effect?

If anyone could offer some insight I would really be grateful. I need my car for work on Monday and I feel like I haven't made any progress. Thank you!