CA Smog Emissions Fail

[bytes311]

Hey guys,

So I took my D in to get it smogged and failed the 25 MPH test. Visual inspection passed, and the 15 MPH test passed, albeit barely. I have been comparing my numbers with others posted here on Talk, and noticed that my numbers are either too low or too high in comparison. Can anyone tell me if I'm running too rich? One measurement that stood out for me was the HC. The 15 MPH and 25 MPH tests measured a constant 6.

My D passed smog last year with a brand new CAT, O2 sensor and spark plug set. Everything is currently stock and operates normally (FV buzzes and there's no indication of a vac leak). I installed Hervey's 3-core brass radiator prior to the smog check. The only thing I haven't done yet is replace the cap and rotor and spark plug wires which are still original to the car.

Thanks!

smog.jpg

[Rich]

....I have been comparing my numbers with others posted here on Talk, and noticed that my numbers are either too low or too high in comparison. Can anyone tell me if I'm running too rich? One measurement that stood out for me was the HC. The 15 MPH and 25 MPH tests measured a constant 6.

Seeing it passes on HC, fails on CO and NO.

Let me know if you need more CA smog test numbers for D's in your area. Am 50mi west of you near SF, can PM lots of them to you for our car.

The HC seems normal or low on your car, suggesting it is not running rich. Maybe the result of the new cat, which tends to mask a rich condition. The report shows the ignition timing is within spec.

Sparkplugs are not old?

Original cap/rotor/wires? You are on borrowed time - replace them all in any case, then retest, assuming nobody finds other potential fixes. You might get lucky. And you need them all anyway.

[David T]

Replace the wires, cap and rotor, I would also replace the spark plugs or at least clean and regap them. If you have anywhere near 30,000 miles you should check the valve adjustments. After all of the work, check the duty cycle on the FV and adjust if necessary. Some other things to do include a new air filter and a tank of fresh gas.

[Ryan King]

Every 2 years I jump through the same CA SMOG checklist. Here is what I do to pass.

1. Oil Change
2. Air up the tires to almost max air capacity (Rolls easier on the machine)
3. Clean my K&N Air Filter
4. Check & Adjust the Dwell
5. Run a can of Sea Foam through the fuel tank (This year I just did one though the mixture control unit.)
6. Changed Spark Plugs
7. Changed out my exhaust gaskets (I have a Stage II)
8. Also I am soaking my Catalytic Converters in Laundry soap & water over night to break down the gunk build up them. Helped me pass last time.

But the biggest one is...

MAKE SURE THE CAR IS HOT AND AT RUNNING OPERATING TEMP.
I live in Fresno, and I take the car on a 45 minute drive down south to Visalia to have it smogged. I always ask them to do it right away while the engine is hot. I also ask them to run their shop fan on my car while they test. I have heard that helps do away with any extra smogging junk in the air while they are testing.

ANOTHER rumor I heard recently was to use steel wool and clean the inside of the tail pipe where they insert the smog probe. Ill try that this year too.

Hope this helps....I am becoming a seasoned veteran of CA Smog.....

-Ryan

[Chris 16409]

I always drive 40 minutes out of town to smog the car to ensure that the engine ant cat are nice and hot. I also fill up with Premium Chevron gas. If the frequency valve is buzzing then we can guess your mixture is okay. Check with a dwell meter if possible.

Looks like Ryan beat me to it!

[Bitsyncmaster]

I always drive 40 minutes out of town to smog the car to ensure that the engine ant cat are nice and hot. I also fill up with Premium Chevron gas. If the frequency valve is buzzing then we can guess your mixture is okay. Check with a dwell meter if possible.

Looks like Ryan beat me to it!

+1

FV will always buzz but is loudest when mixture is close to correct. So check with dwell.

[kings1527]

The DeLorean is a very clean burning car and not hard to have pass emissions tests, even here in CA. High CO and NOX seems to indicate lean mixture, if memory serves. I'd start off with the easy stuff such as ensuring there are no vacuum leaks and checking with a dwell meter first. If you have a relatively new cat and O2 sensor, this shouldn't be a huge issue to dial in correctly. I'm guessing your mixture is off. Here's a decent video (with a tad of hunt) on where the needle should range.

https://www.youtube.com/watch?v=MbE-2k4Cy4E

[Ryan King]

The DeLorean is a very clean burning car and not hard to have pass emissions tests, even here in CA.

Maybe not for a stock DeLorean exhaust. Stage II or after market dual exhaust not so much.

[kings1527]

Maybe not for a stock DeLorean exhaust. Stage II or after market dual exhaust not so much.

Yes, I was referring to a stock exhaust since that sounds like what the OP has.

[DMCVegas]

Fuel mixture on this car is most definitely too lean!

I think that we really need a primer here on what happens inside of the combustion chambers to better understand how to pass smog.

Too rich of a mixture will result in unburned fuel in the exhaust. Gasoline is made from HydroCarbons, hence HC. Your levels are REALLY low at 6, so you've not got enough fuel burning inside of the combustion chambers.

So when we run too lean of a condition, you end up with HOTTER combustion chamber temperatures. This will cause a chemical reaction that gets the inert Nitrogen Gas to bond with the Oxygen molecules. Nitrogen + Oxygen = Nitrous Oxide (in various, indeterminable chains of mono-nitrogen oxides represented by NO & NO₂ which is why we normally represent as NO_x with "_x" representing the mathematical equivalent of the unknown). NO_x is bad. It lowers to pH level of cloud water and creates Acid Rain. This is why we don't want it in our exhaust, and is what VW's cheating scandal is all about.

Since all of that Oxygen is also being consumed by the Nitrogen to create NO_x, it naturally reduces the amount of Oxygen present in the exhaust which in turn destroys the dilution ratio of Carbon Monoxide which causes you to fail in that category as well. It's not that you're producing *more* CO, it's just that the dilution ratio is too low. But a lack of oxygen in the exhaust also hinders performance of the Catalytic Converter to reduce NO_x and starts up a vicious cycle like you have Once you get the lean condition cleared up and the NO, the CO problem automatically clears itself up.

In this kind of case, this is one of three things:

• Vacuum Leak
• Improper Ignition Timing
• Incorrect Fuel Mixture

Go through those things, in that order (with fuel mixture avoided at all costs until it appears inevitable), and you'll have your issue resolved.


Things such as high HC showing unburned fuel is where you start to worry about bad spark plugs and wires, as well as cold engines. Although yes, hotter temperatures can damage plugs.

Speaking of which, here is my recommendation for passing a smog test:

1. Warm the car up.
You've got 3 gallons of coolant pumping through 18 feet of coolant pipes. It's going to take a while to warm the coolant up. The engine may look up to temp according to the gauge, but instead of warm water returning to the engine, it's going to be cold, which can certainly affect emissions when it's still cool out.

2. Burn off all the old gas!
Not everyone uses their car as a daily driver. I understand. But Ethanol in modern fuels doesn't let it store as well, and bad gasoline is going to give you poor results each and every time. So burn it off.

3. Other than Techron, do NOT add anything else to your fuel to "fix" your engine!
There is no such thing as a mechanic in a bottle. Techron is itself a maintenance item, and not necessarily a fix per se. If you're knocking because of carbon build up, you're not going to magically rebuild and scrub an entire engine with one tank of gas. More importantly is that you've got to remember to be very careful. Not all fuel system additives are safe for Oxygen sensors, nor are they safe for older rubber components in fuel systems such as what we have in our cars. So you can do more damage with these concoctions than you think.

Other than Techron, the only other additive you should ever be adding is fuel stabilizer for storage.

4. Give your car an "Italian Tune-Up" before smogging, and every so often as preventative maintenance.
Take the car on the highway, run it at speed, and do NOT engage overdrive! This means you only go up to 4th gear for manual transmissions, and 2nd for automatics. Keeping the engine at load for a prolonged amount of time will increase combustion chamber temps to help burn off some carbon and get the engine nice and warm to properly burn fuel for lower emissions prior to smog testing.

5. There is no such thing as "Premium Gasoline".
It is a myth. Octane ratings have to do with gasoline's resistance to burning. 87 octane has the same amount of energy as 92 octane fuel. There are no additional detergents, and certainly no additional performance boost. Higher-performance engines extract more power from gasoline by way of increased compression, but with the caveat of pre-detonation from higher compression levels. This leads to pre-detonation, or "knock". So higher octane fuels prevent pre-detonation so that the engine can precisely control the burns better.

But in regular cars? Nope. They run like crap because there is no additional heat/compression to burn all of the fuels. Thus it becomes HARDER for your engine to burn gasoline. Which if it can't burn all of the fuel before it leaves the combustion chamber, that leads to higher HC readings on your smog check! Prolonged use of high-octane fuels results in internal damage such as massive carbon deposits. That will lead to pre-detonation thanks to the carbon preventing the dissipation of all heat from the chambers, and then valves which won't close fully because of the deposits. That leads to leaking and a massive loss of power. At that point you WILL have to tear the engine apart to fix it.

Now you do have Top-Tier Fuels which include minimum requirements for detergents to keep engines clean, and restrictions of specific additives. Typically, those are the more desirable fuels you want in your vehicles, and they're the name-brand stuff. Avoid the cheap grocery store fuels and no-name ghetto gasoline.

There is no secret to passing an emissions test other than to ensure that your engine is operating within spec. That's all you need.