Smog Question

[blue1]

It's an 86 22re

Did tune up, plugs, wires, cap, rotor, timing (5deg), valve adj, techron, etc.

I went to get it CA smogged and had high HCs. NO was 50% of max.

Put in a new cat, didn't touch anything else

Next smog--HC was perfect, but NO went through the roof (1700)

Tech told me to check for pre-cat exhaust leak--checked out clean.

Any Ideas to what would spike the NO w/ brand new cat?

 

[justinhw]

Was the cat at optimum operating temperature? You might try driving around for a while beforehand.

 

[CA-RJ]

Agreed. My 86 had crazy high NOX and after replacing the cat things were more in line. Get that cat really hot (30 minute drive) and then go smog it. Leave the engine running the whole time. Have you checked your o2 sensors?

 

[blue1]

Was the cat at optimum operating temperature? You might try driving around for a while beforehand.

Agreed. My 86 had crazy high NOX and after replacing the cat things were more in line. Get that cat really hot (30 minute drive) and then go smog it. Leave the engine running the whole time. Have you checked your o2 sensors?

It was nice and warm during the test. From what I've read, high NO is from too high of operating temps.

 

[corax]

high HC is usually an air fuel ratio that is too rich - too much gas / not enough air to the engine, poor combustion or spark that's letting unburnt gas into the exhaust

high NOx most likely caused by a malfunctioning or plugged EGR or intake vacuum leak

can you take a picture and post the results sheet showing what all the gasses were at?

 

[blue1]

I dont have a camera handy, but here are the before & after readings



With Old Cat

15mph CO2-14.1 O2-1.0 HC-162(max 131) CO-.29(max .61) NO-661(max 1085)

25mph CO2-14.9 O2-0.0 HC-103(max 103) CO-.15(max .77) NO-605(max 1120)


With New Cat

15mph CO2-14.7 O2-.5 HC-4(max 131) CO-.03(max .61) NO-1700(max 1085)

25mph CO2-15.0 O2-0.0 HC-0(max 103) CO-.01(max .77) NO-1093(max 1120)

 

[corax]

The decrease in the HC and CO numbers show that the the first stage of the new cat is working the way it should. Two things come to mind:
- the cat wasn't completely hot since NOx are taken care of in 2nd 1/2 of the cat
- maybe something going on with your EGR - check all the vacuum lines, does the engine stumble/stall when you apply vacuum directly to the EGR valve itself?

 

[blue1]

The decrease in the HC and CO numbers show that the the first stage of the new cat is working the way it should. Two things come to mind:
- the cat wasn't completely hot since NOx are taken care of in 2nd 1/2 of the cat
- maybe something going on with your EGR - check all the vacuum lines, does the engine stumble/stall when you apply vacuum directly to the EGR valve itself?

I'm going to recheck my EGR ( I did it before the initial test). This may be a stupid question, but thats about where I'm at now, could I have put the cat in backwards? Are they directional, or does that matter?

 

[corax]

It should be directional - I know for sure that TWC (three way catalyst) converters definitely are, most everything on the road should have a TWC. There should be an arrow on the cat indicating the flow direction (arrow points towards tailpipe, or "A" for inlet and "B" for outlet)

 

[pyrate]

The cat that you installed, was it for CA vehicles? 90% of the ones you can purchase are not rated for CA smog.

I would check o2 sensors as well.