ok im replacing the o2 sensor this week but i was wondering if it could be anything else i bombed my emissions test i understand it could be any number of things it is very hard to start when cold but once it gets going it runs fine

timing
o2 sensor
intake air temp sensor's how do i test this?
ecu ?

i have no engine light on in the car

 

What year and engine?

 

95 civic dx coupe d15b7 i believe

 

1) Have you checked the condition of the spark plugs, distributor cap, and rotor?

2) Regarding the low idle when cold, check the fast idle valve (see diagram).

3) What parts of the emissions test did your car specifically fail (e.g., hydrocarbons, NOx, etc.)? If only hydrocarbons are high, then check for a stuck open thermostat, an intake air or vacuum leak, an exhaust leak upstream of the O2 sensor, a bad coolant temperature sensor or O2 sensor, or a bad catalytic converter.

 

The most likely reason for failing emissions with no CEL is the engine does not warm up properly, or the coolant temperature sensor is bad and the ECU holds the engine in warm-up mode. Until the engine is at normal temperature, the fuel mixture runs rich on purpose and it will fail on HC and CO.

 

its not so much a low idle when cold its that it just takes 4-5 times of trying to start it to get it going i will check the spark plugs im no longer worried about the emmissions test cause i have a connection to pass but i am worried about why it is running rich using so much fuel and is so hard to start when its cold could it be the timing belt/fuel pump/


and i failed on every level except the gas cap

 

A faulty fast idle valve on the throttle body can cause problems with cold starts. The diagram shows how to check whether the valve is malfunctioning.

With respect to running rich, does the engine take abnormally long to warm up? Is there a crack or leak in the exhaust manifold? Once the engine starts, is the idle speed normal?

 

once it starts the idle speed is a bit off for a minute then it drops down to normal

as for warming up it doesnt take longer than it did

 

Does your CEL work at all? Someone may have disconnected it. It should come on and then go out when you turn the key to the normal "II" running position but don't start the engine.

It's supposed to idle fast when cold.

You don't want to drive much when it is running rich and wasting gas, first because you're wasting gas, and also because such operation will burn out your catalytic converter.

 

sorry guess its just the canadian in me it does idle fast when cold.

sorry what is the cel light and in the first position its supposed to come on and in the second or acc its supposed to go off?