This is a '92 Acclaim 4 cyl. How serious is it to fail NOX emmission? (The guy left me a phone message, so I'm guessing it's spelled NOX.) What needs to be done, and how much should it be?
In case it's relevent, the plugs are past due. Can that contribute because it's not burning clean?
It is spelled NOx, and it means "Oxides of Nitrogen". NOx forms when the combustion chamber temperature is too high. This can be caused by overly-advanced ignition timing, carbon buildup in the combustion chamber (the 2.5 litre engine in your Acclaim does have a tendency to accumulate carbon especially if it's run on cheap "rotgut" gasoline), or a faulty EGR (Exhaust Gas Recirculation) system. The 1992 Acclaim 4-cylinders came both with and without EGR from the factory -- high altitude and California cars got EGR, most of the 49-states-and-Canada cars did not. The EGR cars run better and are easier to get to pass NOx!
If timing is to spec, carbon's been cleaned out with a dose of BG 44K combustion chamber cleaner, and the EGR system (if present) is functioning properly, then the reduction portion of the catalytic converter is likely dead and the converter will need to be replaced.
You mention the plugs are past due. This suggests other periodic maintenance is also past due. The 2.5 litre engine as installed in your '92 has a couple of areas that tend to get overlooked.
Here is a tutorial on PCV system service for the 2.5-- the PCV inlet air filter tends to get ignored because the air cleaner must be disassembled to access it. It's not difficult, but it's usually not done:
And since you need spark plugs anyhow, see if you can find someone to sell you a set of Autolite 925s. These have a double-extended nose and work very well in the 2.5 in place of the standard items, which would be Autolite 65s.
Another thing that will raise combustion temperatures and increase NOx is vacuum leaks. There are plenty of vacuum lines around the throttle body and manifold that tend to crack with age and cause vacuum leaks. The PCV inlet line and all other vacuum lines on and around the throttle body need to be inspected carefully, and any cracked or cooked lines replaced.
DS
Daniel has some good advice. However, before you get all involved, check to see that your cooling system is functioning properly. If you're low on coolant, there is restriction in the system (bad thermostat/waterpump/clogged heater core/radiator), or the fan isn't coming on when it's supposed to, the engine will run hot and you'll get a significant elevation in NOx levels. Failing that, I'd look for a vacuum leak, check the timing and then all the other items that Daniel recommended.
Cheers,
C
When did the 49 state Acclaim drop the EGR? My 1989 2.5L Acclaim was a
49-state edition and had an EGR.Matt
It was sometime between 1989 and 1992.
DS
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