I have a 95 civic LX. I adjusted my idle speed and caused my car to jump rpms from 500-2000. I had it set to high. Once I adjusted it lower, it idled perfectly. It could also be your 0 2 sensor
The intake air temperature sensor on a 2007 Honda Civic is found inside the intake system. The sensor is placed near the air filter box.
IT is a Intake Air Temperature sensor
The intake air temperature sensor on a 1991 Honda Civic is found on the intake. The intake air temperature reads to climate of the air that is being sucked in through to the engine.
Only the 1996 and newer Honda's have a i.a.t sensor. It is located in the air intake tube that runs to the throttle body/intake manifold.
This code is related to the CSF Sensor and it indicates NO signal from it. CSF = Crankshaft Speed Fluctuation This sensor connector is located below by the timing belt (under the intake manifold).
On intake manifold
Close to the Intake Manifold
the sensor is located on the air cleaner housing, right under the air filter.
Just below the intake manifold.
Behind the timing belt cover
In the intake manifold plenium, its a 2 wire sensor
The knock sensor for a 3.5 Honda engine is located on top of the motor under the intake. It is about a 1.5 hour job to replace it.