Hi, so my crx is due for smog and it have the strangest symptom. I discover this when i brought it to the smog station where the guy let my car idle for 40 minute straight. I usually drive my car and shuts it off as soon as I get to the destination. However it tends to overheating if I would leave it at idle for 30-40 minutes without driving. I checked my fans and it does come on. Also replace the thermostat and rad cap. I bleed the whole system with new coolant also. Im just pretty stuck because i need to smog it and it's already pass due. He ran a test on my car and told me it's producing high No(x). What does that mean? My crx is all stock btw.

 

Have ya flushed your radiator system?

As for the Nox

Nitrogen Oxides (NOx)*
NOx is formed inside the combustion chamber when excessive heat is present.

A list of common causes of NOx related smog check failure:

1. As usual check the timing first. Advanced timing can cause extra NOx.

2. The next thing to check is the EGR system.This system is designed to reduce Nox. It consists of a EGR valve, vacuum hoses, one or more vacuum switching valves or solenoids. Its job is to reroute a small amount of exhaust gas back into the engine to help reduce combustion chamber temperature. Not all vehicles have an EGR system.

3. Next thing to check is the air / fuel ratio. If the vehicle is running to lean, NOx emissions will increase.

4. Some possibilities are a restricted fuel filter, low fuel pressure, vacuum leaks, oxygen sensor, load sensor such as a map sensor, air flow meter.

5. Check the cooling system. An extra increase in water temperature will increase NOx production.

6. A defective catalytic converter can also increase NOx. The Cat. reduces NOx that has already been produced.

7. Check to see that the air coming into the engine is not over heated. Some vehicles have a vacuum controlled air valve which switches the incoming air to hot air from the outside of your exhaust manifold.This should only happen when the engine is cold. If this system malfunctions and sends hot air all the time.Your Nox could go up. This system is called T.A.C. ( Thermostatic air cleaner )

8. There is another system similar to the one above called E.F.E. ( Early fuel evaporation ). This system routes hot air under the intake manifold. This helps keep the fuel in the vapor state. If stuck in the hot mode Nox emissions could increase and cause a Smog Check failure.

 

Did you use OEM parts for these? Did you follow the manual's instructions exactly for bleeding the system, including the roughly 40-minute wait for the fan to come on twice?

If you did all this, you need to start monitoring your coolant reservoir level and looking for other symptoms of a blown head gasket. Especially since the car has overheated before.

Fix the overheating issue first. Then work on passing the smog check.

 

Thanks for reply so far. I am trying to fix the overheating issue before I get it smog. O and to clarify things, it didnt overheat yet, temp was rising and seem like it will start to. Sorry for bad info.

Unfortunately I was told that I didnt need OEM for the cap and thermostat. I bought it from autozone. As for the EGR system, is it located on the head? right behind the distributor? Because it have a block off plate right on it, Im guessing to stop oil from leaking. Yes I did flush my coolant system, and I believe it bleed it correctly (got from H-T).
1. put car on ground level
2. open rad cap, turn heat to max.
3. turn car on with cap off.
4. watch as air bubble comes out the fill neck, and top off when necessary

How would I check for air/fuel ratio? And where is the TAC located?

 

here's a question, how does your radiator look? are all the fins okay? like not bent restricting air flow?

 

How many miles are on that water pump?

 

It remains more likely that a breach of the head gasket occurred even with this little overheating. You might be fine; just be alert to the possibility the head gasket has failed.

The car is not supposed to overheat at idle. Most likely causes: the thermostat is wrong; the rad cap is wrong; head gasket breach; leak somewhere like at the water pump; blocked radiator.

Without an OEM rad cap and OEM thermostat, further diagnosis would just be wild guesses.

This is no where near good enough. Your system may very well be full of air. Follow the shop manual's instructions here: http://media.honda.co.uk/car/owner/m...SH200/5-59.pdf

While bleeding the system, it may take 40 minutes or more for the fan to come on twice.

 

have you looked at your water pump?

 

[QUOTE=sleepingciv;36610189]Have ya flushed your radiator system?

As for the Nox

Nitrogen Oxides (NOx)*
NOx is formed inside the combustion chamber when excessive heat is present.

A list of common causes of NOx related smog check failure:

1. As usual check the timing first. Advanced timing can cause extra NOx.

so i eliminated to this, i fixed the timing and amazingly it doesnt overheat any more. but now my fan just stay on constantly. it doesnt turn on when its cold. only when its warm up to the point where fan should kick on and it just stay on.