Hi, it seems that my '93 Del Sol Si (I bought a month ago) is not able to pass a smog check here in California. Funny thing is, the guy who did the check gave me the smog history of my Del Sol and it looks like this:

CIVIC DEL SOL|1993|03/04/2016 02:40pm| F | (Current, not included in actual list.)

CIVIC DEL SOL|1993|06/04/2015 04:06pm| P |
CIVIC DEL SOL|1993|06/04/2015 11:03am| F |
CIVIC DEL SOL|1993|08/19/2014 09:34am| F |
CIVIC DEL SOL|1993|04/16/2013 04:52pm| P |
CIVIC DEL SOL|1993|09/07/2010 01:53pm| P |
CIVIC DEL SOL|1993|03/03/2009 03:22pm| P |
etc. (passes all smogs back to 1997)

The guy who did the smog, said he didn't know what could be causing the problem etc. "Come back next week and I'll do a diagnosis for [insert price here]".

So what do you think could be causing it not to pass? Here is the actual result sheet of the smog:



Thanks

 

What engine and ECU?

 

It's a D16z6 and I think p28 ecu.

 

Find the ECU and make sure. It should be behind the passenger side kick panel.

 

confirmed p28

 

The catalytic converter may be bad.

 

Luckily for me, I live in California which is the only state with special needs in terms of cat. converters. Is there any other options than OEM if I have to replace the catalytic converter?

 

What gas are you using? When was your thermostat last replaced?

 

The car was bought about a month ago and has only been driven a couple of times during the period I've had it. The last person to fill it with fuel was the previous owner and I don't know anything about the maintenance it's had.

 

Well a cat can cause that, but so can a few other things that are less expensive than a cat. Start off by draining the tank, or driving until it's empty. Re-fill with 85 or 87, whatever "low grade" you have. Replace your thermostat with an OEM unit. Get it from the dealership.

 

Do you think it could be something wrong with the engine itself? Or what would be the worst case scenario?

 

Not wrong, per se. There's a chance that a massive amount of carbon buildup could cause the problem, but let's not worry about that bridge until we've reached it.

 

I guess according to the result sheet, the CO is way higher than average. So I looked that up and all the common causes for high CO is all related to sensors (O2, MAP, TPS, ECT). Maybe one of those are bad?

I'll also try to use the rest of the fuel and fill up with regular since there's only a quarter of a tank left.

 

High CO fits with the engine running slightly rich (high HC), which is also evident in the emissions sheet.

When both HC and NOx are high, the cat is usually bad.

 

Probably a dumb question but... If I end up having to buy a new cat., would an OEM one be compliant to California's emissions bs?

 

Talk to the smog tech and to a manager of an auto parts store like AutoZone. They should be able to guide you.

 

didnt fail that bad. retard the **** out of your ignition timing, if it still fails, alcohol in gas. lots.

 

Definitely get rid of that old gas. If you have the California model with EGR, clean out the EGR system. EGR is mostly to reduce NO though. That won't help HC or CO, which you're also failing or very close.

 

seafoam through the brake booster vacuum leading into the intake manifold with some new plugs should help allot. Im assuming your check eng isn't on right?

 

No check engine light.

 

at 15mph your NO is high i had this problem and a oil change, air filter, spark plugs, and 02 sensor fix it for me.

as for the cat i have stock and the heat shield removed with a catback system and passed. for your question about the cat check out this page: Replacement Parts Guidelines - Aftermarket, Performance and Add-On Parts Regulations under Catalytic Converters

a consider list:

• check fault codes
• make sure your timing is in check
• do a tune up (timing belt, water pump *since your in there*, dizzy cap and rotor, wires and spark plugs)
• oil change
• air filter
• clean or replace map sensor
• fuel filter

those are big things that help with California smog. the rep for me even said a fuel pump thats failing and not outputting the correct psi can also cause it to fail

 

Seafoam and new plugs, also do a oil change after 25 miles of driving on the engine hard right after the seafoam and i mean hard (4500+ rpm up a hill if possible). Make sure to keep the rpms up enough to keep the car from dieing out when you vac the seafoam into the mani, also run a entire quart of oil through the engine when you do the oil and filter, this will get allot of the carbon out as is worth the $5 waisted oil. Mobile 1 and a bottle of lucas, then hit that smog again see how you do.

 

with no codes its a carbon issue if one bottle of seafoam and oil change doesn't do it, do it again. Your cars gonna smoke like a Nuke though for the day whole lot of fun lol

 

Not sure how you can come to this conclusion. There are clearly other possibilities.

 

Close but failing on all 3 is very often a tired cat. The OBD1's do not have a sensor after the cat to throw a P0420 code.

Again if you have an EGR system on yours, take off the valve and open the plate on the top of the intake and scrape the carbon out of the passages manually. The cleaning ability of Seafoam is highly exaggerated. Interestingly you can apply it to a brand new car which is clearly clean inside and make exactly the same wall of smoke.