Failed hc ppm - 1993 Nissan NX

Hi!

First of all, HC (Hydrocarbon) are the residue of petroleum based product combustion. If your HC reading are higher than the OBD2 legal limit (220 ppm), the most common causes could be a leaking fuel injector, abnormal oil consumption, a faulty Oxygen sensor or worn out spark plug / distributor cap / spark plug wire. To be honest, I would need more accurate details such as NOx ppm, CO ppm, CO2 ppm and Oxygen ppm and if there is any repair that have been made on the car recently to give a proper diagnostic.

Warm regards

put a muffler on it

If I read your post right, you are over on Hc and that is all? Check the air filter, check the injectors. You are either not getting enough air or are getting too much fuel.

wow, no context but i can read your mind?
ok SMOG failed. right?
what speed, there are 2 in uSA, 15 and 25.mph.
so there are 3 tests, which one. all are PPM in usa.
parts per million.
but is that HC , CO, or NOX? or ?

based on your numbers is HC
hydrocarbons or in barstool, its raw gasoline leaving rear of car.
unburned fuel..

572 ppm is way too high 12-19 is normal
id say the CAT is bad.
but can be , engine is bad, and burned out the cat.
that is why all savvy mechanics, check the that the engines
holds closed loop status, (EFI closed loop) at the speed yours failed.
if not in closed loop the cat will burn up (rich)
that is first.
Once that is cured. you check HC again. if out of spec
you did burn up the can , new cat time.

that is the correct way.

Any codes? any problem tune up, catalytic convener, burning oil.

i can be, only 2 things, or both.
1: engine running way too rich.
2: dead cat.
(both happens, too)
replace the cat, might be cheaper that full engine diagnosis and repair.
in a real shop we test the cat. using up and down stream tests.
with the 5 gas analyser.
but the truth is a new CAT can hide a very filthy running motor.

run the fault codes to find the faulty sensor
sensors that control the exhaust emissions are the HO2S ( heated oxygen sensors in the exhaust manifold/s
the O2 sensor ( oxygen sensors after the cat converters ) and the EGR unit that recycles exhaust gas back through the engine to re-burn the gasses

possible but could be head gasket or valves , or worn rings and is by passing the pistons going straight out the end ...or maby settings are wrong ? try carb cleaner and inspect visually air-filter etc.

have you had the the engine codes pulled and reset?
and if so what are your engine codes?
i dont know of any car that will pass emissions test with the engine light on.
we cure your trouble that caused your engine light to come on and you will pass your test.
later
paul