Failed inspection on emissions... what's the problem?

[Danrc30]

My readings for HC (hydrocarbons) and CO (Carbon Monoxide) were too high at inspection today. What could be the cause of this?

[180fan]

what were the numbers and what year and car?

[Danrc30]

HC is supposed to be 136, mine was 302

CO is supposed to be .76, mine was 7.36

car-> 1993 vert

[rogoman]

Have you done the usual maintenance:- replaced spark plugs- replaced air filter- checked the ignition timing

[Danrc30]

I tuned the car up 2 years ago when it went though inspection last... plugs, wires, cap, rotor, air filter, and O2 sensor. It may have 20k on it since the last tuneup... it shouldn't need to be replaced already... I'm lost here...

I just fixed an exhause leak at the rear flange of the cat. I took the cat off and it looked clean, so that should be fine too.......

[Q45tech]

Depends on the quality of the O2 you used for replacement........if it is switching properly [cross count test] then look at the cat condition [test functioning with before after temperature.

[Danrc30]

How do I test the O2 sensor and cat?

[Danrc30]

Anyone???

[Q45tech]

Use a Consult scan tool to view the voltage shifts and graph and analyse the switching time [or just replace the O2].

Use an IR temperature gun to measure the fore and aft temperature of the cat.

Use you 5 gas analyser to make changes and view emission results.

Most don't have these expensive tools at home why you pay a expert shop that specializes in Nissan to conduct these tests for you.

A digital storage oscilloscope can be used to directly monitor the O2 but most don't have one of these either.

[Danrc30]

Ok, I'm noticing a problem here that may be related... when I hit the clutch and come to a stop, the rpm's go so low, it almost stalls. Then the rpm's stay low and it pulsates a little bit.

Does this help?

[NISTECH]

Your car is running pig rich. With those numbers you are dumping gas into the cyls. Because your HC are so low and your CO are so high its obvious your engine is trying like hell to burn all the gas its getting.

Couple questions was this an ASM(acceleration simulation mode[on a dyno] or TSI (two speed idle[rev the engine alittle in park] test.?

Also can you post all the mesured numbers from the test? Not just the failing gases.

With an engine that rich you should be looking to see if the engine coolant temp connection is clean, measure the resistance on the sensor cold and hot. Also you want to look at airflow readings, are they high at idle? you may want to go as far as hooking up a fuel gauge and do a fuel leak down test to see if an injector is leaking.

Your low idle may be an inditication you got to much fuel in there as it comes down to idle and that fuel is possibly about extinguishing the spark. Fuel wont burn as a liquid in there, it needs to atomise.

[Danrc30]

Well, I figured out the problem. The solution came from a friend of mine, and not this forum. Which suprises me because of all of the accurate help I've recieved in the past from this group...

The culprit was a bad PCV valve. The valve was plugged so it was forcing oil into the cylinders. This is why I was burning oil, why the car was running poorly, and why there were oil spots all over the rear of the car...

What a pain in the a$$ this was to change... took me several hours and lots of cursing before it was fully installed...

Now I'm doing the regular tune-up to freshen it up, and all should be good...