89 spirit 2.5 TI emission failed - Georgia

[pyrofenix]

I just got back from an emission test for my 1989 Dodge Spirit 2.5 TI which failed it's Georgia emission test.

Here are the test results (i'd REALLY appreciate any thoughts on what to look at/replace/fix).

25/25 Test: HC-ppm: Pass CO-%: Pass NOx ppm: Fail (reading: 1325 allowed: 1208)

The NOx ppm test passed on the 50/15 Test. Thoughts?

[pyrofenix]

Of note the car is running 3" exhaust w/ cat that has very few miles on it. The head was replaced within the last 6 months as well.

[NAJ]

NOx is created by heat. O2 and Nitrogen will not combine if the temp is below 2500 deg F
or under pressure(Nitrous Oxide)
Be sure that your basics are correct,cooling system and base ignition timing etc.
Also in N.J where the emissions standards are very tough a lot of aftermarket Cats are not efficent enough to clean the exhaust to N.J.'s emissions standards.If that is the case you will have to put a factory cat back on or do as my Son did on his 94 Duster
3.0L.He has aftermarket exhaust and CAT and he was working at a muffler shop at the time and he failed for NOx and he went back to the shop, put another CAT inline so he had 2 and went back,passed the emissions test and then removed the 2nd CAT.

[pyrofenix]

Thanks for the info. I don't believe the issue is around the CAT as it had passed when it was initially installed.

The head replacement came as a result of cooling system failure (replaced the radiator) and it seems to run in normal operating temps but i'll take a look at that and timing - possibility that timing is off slightly after new head was installed.

Thanks again!

[NAJ]

Since the head was off be sure that the Cam timing is correct.
Be sure that the plugs are free of deposits that may be causing them to get to hot.

[LynX853]

put alcohol in the take and let her eat!

[tryingbe]

Let me guess, Catco cat?

Do you have any exhaust leak in front of the catalytic converter?

[glhs0426]

NAJ is correct NOx = heat, a lot of it.

HC was a pass so the cat is working properly.

CO was a pass so you have no exhaust leak.

Check your base ignition timing for being too far advanced.

Was your cylinder head milled? If so, it could have changed the cam timing, but it would have to be a good amount. .040" or more to affect NOx.

[crazymadbastard]

I passed in connecticut with a catco. Sniffer dyno and visual
Running gas dryer does work, my guess is the alchohol will make things burn cooler and cleaner.

[pyrofenix]

Yeah, a catco 3" cat. No exhaust leak & no head milling was done. I'll check into the cam timing and then consider gas dryer/alcohol. I'm also going to grab some new plugs just in case (it can't hurt).

Thanks a lot for all the suggestions!