failed california emissions

[willabeest]

any ideas? drove vehicle for 50 miles before testing. (it was warm).

1992 NSX 86,000 miles
comptech headers. otherwise engine is stock.

CO and NO passed.

HC failed at 1557 RPM 15 MPH. Max is supposed to be 114 mine was 171 PPM.

HC passed at 2443 RPM (25 MPH). (barely passed).

any ideas what usually is the problem? TIA.

 

[NSXT]

Clean/replace the air filter.

 

[willabeest]

Clean/replace the air filter.

thankyou! i will do that. anything else? i get one free test having failed one already. TIA.

 

[NSXT]

Perhaps cleaning the TB while you're at it. In my experience, when other gasses look good but with high HC, the air filter is usually very dirty.

 

[RON98]

hi HC = engine running too hot.... or too cold.......... i think its running too hot.

it was a while ago i did my smog so im rusty.

Anyways, always do a complete tune up before smog. Spark plugs, oil change and definitly change your Air filter if it is dirty.

Before you go. Add a bottle of octane booster to your gas tank and gas on 91 octane gas. Make sure to drive the car on the high way and get the engine up to speed so the cats get into operating temperature.

When you arrive at the Smog place, tell them to put the car on the test asap. If they cant do it, just leave the car idling. They should be warming up your cats for a 1 minute or 2 before the test by keeping your car at high revs.

After that, you should be good to go.

 

[BryanZublin]

The engine will be running in closed loop mode during the test, so the most important things that must work are the catalytic converters and the O2 sensors. A failing O2 sensor will cause the engine to run rich (high HC emissions). Have the O2 sensors ever been replaced in the last 86,000 miles? If never, it's probably time.

A dirty air filter will have insignificant effect during the smog test since the air flow is very low.

 

[willabeest]

The engine will be running in closed loop mode during the test, so the most important things that must work are the catalytic converters and the O2 sensors. A failing O2 sensor will cause the engine to run rich (high HC emissions). Have the O2 sensors ever been replaced in the last 86,000 miles? If never, it's probably time.

A dirty air filter will have insignificant effect during the smog test since the air flow is very low.

AFAIK the O2 sensors have never been replaced. when do they usually go in a 1992 NSX?

 

[Racerxjling]

IMO O2 sensors is the ticket due to mileage. Either way, it would be good preventive maintenance.

Jeff

 

[willabeest]

IMO O2 sensors is the ticket due to mileage. Either way, it would be good preventive maintenance.

Jeff

maybe that is the next thing to do. i saw this

http://www.4x4wire.com/toyota/4Runner/tech/O2_Sensor/

 

[gabej]

hi HC's = unburned fuel......O2's (lazy) maybe, could also be secondary ignition components, (plugs)

 

[willabeest]

hi HC's = unburned fuel......O2's (lazy) maybe, could also be secondary ignition components, (plugs)

i wanted the plugs changed but the technician said it was not necessary.

 

[W]

High hydrocarbons mean unburnt fuel as mentioned above. RON98, it is not related to combustion being too hot. High combustion temps lead to high NOx readings. That's what the EGR valve is for. Yeah, I know. Re-route really hot exhaust gas back to the combustion chamber to reduce the temps? It really does work.

What sort of fuel economy are you getting? What type of driving?

I would change the oil (contamination of the oil with gasoline), add a bottle of Guaranteed to Pass, run the tank low (as directed on box), fill up, go to the test station, rev the motor for a couple of minutes right before the test (at say 4000rpms), then immediately onto the test. The revving is to keep the cats 'awake' as they do 'fall asleep' quite quick and take a bit of time to 'wake up'.

 

[willabeest]

High hydrocarbons mean unburnt fuel as mentioned above. RON98, it is not related to combustion being too hot. High combustion temps lead to high NOx readings. That's what the EGR valve is for. Yeah, I know. Re-route really hot exhaust gas back to the combustion chamber to reduce the temps? It really does work.

What sort of fuel economy are you getting? What type of driving?

I would change the oil (contamination of the oil with gasoline), add a bottle of Guaranteed to Pass, run the tank low (as directed on box), fill up, go to the test station, rev the motor for a couple of minutes right before the test (at say 4000rpms), then immediately onto the test. The revving is to keep the cats 'awake' as they do 'fall asleep' quite quick and take a bit of time to 'wake up'.

driving is mostly to and from work, sometimes i head for the hills but usually about 20 miles a day. never checked mileage. i change the oil every 3000 miles use synthetic. it was a cold morning when i had it tested. the tester had never seen an NSX before so maybe it did cool down even though i took it in there very hot (85 MPH for 20 minutes).