Help me Pass Emissions!

[Toplevel4ever]

Ok guys. So i picked up this 1990 240sx last year that was all in pieces and im now done getting it back together and trying to get it through NJ inspection. I am failing for emissions.

IDLE-FAIL
HC ppm reading 387, standard is 220
CO% reading 3.32, standard is 1.20

HIGH IDLE-FAIL
HC ppm reading 266, standard is 220
CO% reading 0.71, standard is 1.20

It's a 1990 with a 1993 ka24de swap. A few things that im thinking could be the problem. It has aftermarket intake piping, and exhaust header. The EGR valve is not hooked up. The idle is high at about 1000-1100 rpm. Yes it has a cat on it.


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[S14DB]

How old is the Cat?
How long did you drive the car before the test?
When was the oil and spark plugs changed?
New gas?

[5280VertDET]

Fact: Green Valve Covers wont pass smog.

[Toplevel4ever]

Haha yes. The valve cover was that color when I bought the car. The cat is new. The plugs are whatever the previous owner put in there so I'll change those. The car was driven maybe 15 minutes before the test. The engine oil is probably close to a year old but with maybe 100 miles on it. And the gas is new.

[silverarrow27]

Crap, I'd never drive a car with a yr old oil. I'd go back stock exhaust manifold and intake to begin with and hook up your EGR system up.

[S14DB]

Crap, I'd never drive a car with a yr old oil. I'd go back stock exhaust manifold and intake to begin with and hook up your EGR system up.

EGR would affect nox levels.

Also, check for vac leaks.


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[Toplevel4ever]

EGR would affect nox levels.

Also, check for vac leaks.


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So then I shouldn't have to worry about the egr valve? I don't see nox listed on the paper.

[S14DB]

So then I shouldn't have to worry about the egr valve? I don't see nox listed on the paper.

You are failing HC. You are having a combustion problem. Why I suggested the checks and changes I did.

[l adam l]

I've heard methanol alcohol will help you pass.
As he said hook the egr back up. stock mani, intake, etc... cant beat stock for passing emissions

[jscherf92]

Don't rely on tricks and cheats for this, emissions are more than just a legal requirement and in this case they are pointing towards possible engine issues. Do the plugs and oil change, a seafoam treatment wouldn't hurt, a tank of fresh higher octane gas and inspect everything for possible leaks that point towards that high idle.

[SimpleSexy180]

you don't half a header not liberally but a verbal thing around smog technicians, any verbal continuum about halfing headers can't distribute even shifting through a...

[Toplevel4ever]

you don't half a header not liberally but a verbal thing around smog technicians, any verbal continuum about halfing headers can't distribute even shifting through a...

I have no idea what you just said :confused:

[jedi03]

Rofl hook up your factory emissions stuff an make sure you have fresh oil and good fuel run till hot ansea foam will be a good idea...

[Chaluska]

High HC is caused by a incomplete burning of fuel. weak ignition (old coil / spark plugs / plug wires), leaking fuel injectors or running rich (dirty MAF / vacuum leak), the catalytic converter removes unburned HC so the cat may be worn too.. remove it and see what the mesh looks like. these can be burned all the way thru over 20 years of use.

the EGR valve wont make an effect on HC. that will cause your NOX to be sky high

[Toplevel4ever]

The cat is new. I just changed the plugs and did an oil change and I can tell the difference already. Running smoother. It did not have oem style plugs in it so I corrected that. It doesn't have the pair valve hooked up either. I guess that could be an issue. I'm going to hook up the evap canister, maybe the pair valve, check the timing and adjust the idle if need be. I'm going to take it back to inspection this Saturday.

[milto0n]

Check free stuff first: Usually all those little hoses behind the engine. Total PITA to get to but you'd be surprised how often they crack/ fall off. Check for vacuum leaks. You'd be suprised how often things just aren't tightened enough. Check for exhaust leaks. You said your EGR wasn't hooked up. That difficult to undo hard pipe that runs from the intake mani to the exhaust mani recirculates combusted exhaust back to the intake and is essentially what EGR is. And yes, hook that evap canister back up to save you a little gas money (and potentially your gas tank from exploding if not deleted properly!) I'm surprised your numbers aren't higher quite honestly but I haven't done smog in a while...

[S14DB]

High HC is caused by a incomplete burning of fuel. weak ignition (old coil / spark plugs / plug wires), leaking fuel injectors or running rich (dirty MAF / vacuum leak), the catalytic converter removes unburned HC so the cat may be worn too.. remove it and see what the mesh looks like. these can be burned all the way thru over 20 years of use.

the EGR valve wont make an effect on HC. that will cause your NOX to be sky high
Exactly. Only time the EGR will mess with HC is if it is leaking. As long as it was deleted properly it shouldn't affect the HC. If there is a Vac leak or the exhaust plug is letting air in. It could affect the AFR.

[jza80king]

High HC is caused by a incomplete burning of fuel. weak ignition (old coil / spark plugs / plug wires), leaking fuel injectors or running rich (dirty MAF / vacuum leak), the catalytic converter removes unburned HC so the cat may be worn too.. remove it and see what the mesh looks like. these can be burned all the way thru over 20 years of use.

the EGR valve wont make an effect on HC. that will cause your NOX to be sky high

Agreed with this....I would also suggest changing the PCV Valve. This will/might reduce hydrocarbon numbers. I just recently bought about 15 feet of vacuum lines and carefully went thru and changed all the vacuums on my car and it helped make the car run better also. Some of my vacuum lines were def leaking so it caused issues upon emissions testing. If changing plugs made a big difference, you might consider changing plug wires if they are old also.

[godsmack]

I'm wondering why everyone is saying vacuum leaks when HC's are high?

Of course check those but he's getting too much fuel in there or not enough spark. Vacuum leak will cause a lean condition not a rich one.

What is a pair valve?

[S14DB]

I'm wondering why everyone is saying vacuum leaks when HC's are high?

Of course check those but he's getting too much fuel in there or not enough spark. Vacuum leak will cause a lean condition not a rich one.
You can get a lean misfire condition where the engine is to lean to fully burn or even ignite also.
What is a pair valve?
AIV