Failed Emissions Inspection?

[BiXLL]

I have a 93 KA24DE in my 240sx. It runs smooth, no shaking or missing. I am getting 25 to 27 mpg city driving. I stay on top of the maint., air filter is new, oil was just changed. I went to have my State inspections done yesterday and was floored when they told me it failed emissions.

On the CO, I am allowed 1% and I showed a reading of 5.13%.
On HC (hydrocarbon) I am allowed 130 ppm and showed 320 ppm.

I have no engine lights on, spark plugs are year old platinum tipped. I am absolutly stuumped. I would think that for the readings to be that far off the car would have to be barely running?

I have put a can of Seafoam fuel system cleaner in the tank and am running it through, but I really don't expect it to change anything. Any ideas/suggestions????

[vocationalzero]

do you have all the emissions stuff hooked up? i.e. catalytic converter, egr system, vacuum canister, etc. does it smell like sulfur/rotten eggs when you drive? (tell tale sign of a bad catalytic)

[BiXLL]

yeah, everything is hooked up, I am completly stock, no mods done. I have not noticed any smell, and I don't think checking it now with the seafoam in there is going to tell me anything. Can a cat go bad just that quick with no other symptoms or indications? Like I said, I am STUMPED!!!!!!

[Wc240]

how quick are you talking about? how old is the cat? they can go bad in a week, or last the lifetime of a vehicle. where are you located anyways? if your possotive everything is good, id check the timing, if thats good, look into getting the cat tested

[BiXLL]

how quick are you talking about? how old is the cat? they can go bad in a week, or last the lifetime of a vehicle. where are you located anyways? if your possotive everything is good, id check the timing, if thats good, look into getting the cat tested

I am 25 miles northwest of Pittsburgh. How do you test the cat??? My son is telling me about an additive he used to pass an emissions called "Guarantee to Pass", anybody ever heard of this stuff? If timing was off would it not make the engine run ruff, or shakey?

[BiXLL]

Well, I ran half a can of carb cleaner through the vacuum hose to the air box thing where the idle adjustment is, changed plugs, and ran a can of Seafoam though the gas tank. My air filter is new and the oil was just changed. I just got back from the inspection station and not only did it not pass, the numbers were worse!

It is idling as smooth as silk, has no misses, runs great! No codes have been thrown, but the exhaust does have a strange smell to it. Not the rotten egg smell, but strange. I am at a loss once again, as if either the O2 sensors were bad or cat bad it show throw a check engine code????? I don't know where to go from here!

I just do not know where to go or what to change from here to get it to pass. I hate to go and change the cat or O2 sensors only to get the same results, which I have a feeling I would get because of no codes thrown for those items being bad.

Any ideas guys?

[Klits562]

with high CO and High HC its kind of tricky cause HC is caused by a lean mixture but CO are usually a rich mixture so i would guess your O2 sensor could be giving a bad signal to the ecu. The o2 sensor is constantly changing your mixture from rich to lean very rapidly. A bad o2 sensor will still send a (incorrect)signal to the ecu and because the ecu is still getting a signal it wont through a light.
Also check your ingition system i would replace the plugs wires and cap. Also test the coil(idk how to :P)

[BiXLL]

It was the o2 sensor. I changed it and car passed emissions easy. Thanks for all that responded.