Failed Smog in CA

[n01d3x]

So glad to have found this forum, seems like I will be visiting here a lot.
I just bought a '93 Civic Dx as a commuter. It has about 140,000 miles on it and is an automatic. Sometimes on take off it stalls and lags out a little, then goes away. This does not happen that often and didn't when I test drove it. It failed smog today, but only in the 25mph NO column.
15mph NO (PPM) Max 731 MEAS 715
25mph NO (PPM) Max 798 MEAS 1010
Everything else passed pretty well below the MAX range. It barely passed the 15mph NO test. From what I've read seems like maybe the cat?? I have not done anything, but am going to change spark plugs and wires just because. Any input is highly appreciated.

 

[RonJ]

Replace the fuel filter and set the ignition timing to spec using a timing light.

 

[colecivic]

fuel filter or cat

 

[n01d3x]

Do you think the high NO and the lagging are related?

 

[colecivic]

well remember any time ur gonna smog ur car..fill up with premium gas. mobil 1 oil. go run the car in the freeway and then go smog it..helps u pass the car

 

[n01d3x]

Thanks, I'll replace the fuel filter and change the oil and make sure to get the cat warmed up before I go. I do not have a timing light, I was thinking about getting the timing belt changed anyway since I have no idea when it was last replaced. They would make sure the ignition timing was in spec while doing that right?

 

[RonJ]

Do you think the high NO and the lagging are related?

Almost surely. That's one reason to think the cause is not a bad cat, which would generally cause the car to fail both HC and NOx.

 

[RonJ]

I do not have a timing light,

A timing light is relatively inexpensive ($15 - $30). You may also be able to find a free rental at an auto parts store.

When was the timing belt last replaced?

 

[n01d3x]

Oh, I just did a quick google search and found ones in the $100 range. Didn't think about renting one, I'll give it a shot. Thanks for the diagram. Seems easy enough. It would be great if both problems were fixed with the same solution. Thanks for the advice. I'll let ya know how it goes.

I do not know when the timing belt was replaced. Like an idiot I didn't ask when I bought the car.