Failed SMOG High NOX at 15mph

[cdmcali]

Hey everyone,

I went to go get my DeLorean smogged last weekend and it failed the 15 mph NO test. It measured 1269 aand the max is 1148. In the 25mph test it measured 935 with a max of 978. The tech recommended that the O2 sensor be replaced but that was already done about 2 years ago. I took it for a good drive before the test to get it nice and warm. Any thoughs on what could be causing the issue or how to get it to pass. 2 years ago I had the engine tuned up at DMC california and haven't noticed any issues with it. Thanks in advance! 56593

[David T]

Get a fresh tank of gas and run a can of Techron through the motor. If that doesn't work you may need to go back to DMCCA and get the car tuned up.

[cdmcali]

Get a fresh tank of gas and run a can of Techron through the motor. If that doesn't work you may need to go back to DMCCA and get the car tuned up.

Thanks David. Do you have a link for the Techron you recommend? Also, would running a higher octane just for the test help?

[David T]

Any large automotive supply should have Techron. Higher octane won't do anything but fresh gas (the right octane, regular) certainly will.

[Ras12]

I never believed in additives and always thought they were gimmicks. Then I had a check engine light, it was running rich, and didn't pass inspection on my 2007 Yukon Denali. The sales person at O'Reily Auto encouraged me to try SEAFOAM in my gas, crankcase and more importantly trickle a full can down into the engine via the brake booster vacuum line. I did this and remarkably it ran 100% smoother and passed inspection with flying colors. I tried it on my Delorean with the same results. One word of caution, when you add the additive and drive the car you need to get on the highway or rev it up and you will create a smoke screen of white smoke. Check out some SEAFOAM videos on YouTube and you will see what o am talking about. Good luck!

[David T]

A Delorean's fuel system is nothing like a 2007 Denali's. All you have to do is clean up the mechanical fuel injectors to get a better spray pattern. It also doesn't
have to meet as stringent a standard as the 2007 does. Seafoam can also work but I don't have a lot of experience with it, I do with Techron.

[Chris 16409]

Does your car have an original exhaust system? The original cat is very good at scrubbing the exhaust gases. If you have a stage 1 exhaust, they are known to be not as efficient with NOx. I also get close to the limit on NOx with my Stage 1. If your original OEM cat has higher milage it may be time to replace that. Also check your CO mixture to see that you are in the proper range.

[NckT]

You could go back to basics, take your air filter out and see how dirty it is, and consider replacing it if it is dirty. New engine oil, check the spark plug gaps etc.

Checking the switching of the o2 sensor would be a good, but the sensor just senses the oxygen content, not the burn quality of the fuel.

If the re-test is free, as a quick fix you could drain off old fuel and make sure there's plenty in the tank of fresh petrol. Once you've got the pass you could re-use the old fuel in 1 to 5 ratio to use it up.

Good luck

[ritztoys]

I use this fuel injection cleaner, it is specially formulated for our Bosch fuel systems. I swear my mpg is better after I have added this to my gasoline (x2 year)

56597

Yes, that's 04629 in the background almost ready for driving season!

[ritztoys]

Hey cdmcali

Not to hijack this thread of yours, I just noticed your car and mine are only a few digits apart! Very cool since mine used to reside in Hawaii, until I moved back to the mainland.

(Mine was originally sold by a Honda dealer near Long Beach)

[TTait]

High NOX can mean the combustion temp is also a bit too high.

The engine should be warmed up, but not running hot. If it was just a bit cooler you may have passed. Hotter is not better.

Your cat may be a little tired too, but I'll bet if you put on a fresh 02 sensor, check that your WOT switch isn't stuck, and test again a little cooler you will pass.