It's SMOG time - Questions about Gas Caps & C/O Mixture & Timing Advance

[Chris 16409]

I just failed by SMOG inspection due to a combination of a bad gas cap and a too high NOx value at the 25 MPH test. I was told the NOx are supposed to decrease with a higher C/O mixture. Has anybody adjusted this themselves? I know you are supposed to use a wideband O2 sensor, but can you do it manually? Josh Bengston said the value should be at 14.7.

On the gas cap front, I seem to remember hearing this is a problem area. I know Houston has reproductions available. If any of you have any experience with these, have they been trouble free? I don't want to buy a new one if it still won't hold pressure. Does anybody have any aftermarket suggestions on gas caps?

My buddy Ryan will chime in on the timing advance. The sort version, his engine is set at like 19 degrees because he has Stage II. That of coarse is not stock spec, so they failed him for that.

We'd appreciate your input, thanks.

Oh and remember we're in California so we have to deal with more bull crap!

[Ryan King]

Here is my print out from the smog shop... :/

scan0002.jpg

[Cory W]

I bought a new cap a year ago from Midwest. It's a better seal than the one I took off the car. Your fuel cap pressure should be no problem with one.

[Ryan King]

The Smog Shop owner was saying that I need to have my distributor adjusted to put it back into spec for timing. I tried explaining to him that my car has a bigger engine with larger cams. But he insisted the distributor has to be corrected. He wants to charge me 44 dollars to do so.

[TTait]

Ryan/Chris...

We've talked about Ryan coming down anyway... I've got a guy thats cool - that said he will not pass the car if its not running right - but there isn't going to be any BS about distributor advance or any of that. You might plan on tweaking the mix a hair and then redoing the inspection down here.

For anyone else in the LA area (SF Valley actually) I highly recommend http://www.joessmogcheck.com/

He does all of my cars, and now he does many of my friends too...

My car has the same distributor timing as yours - no problem there. I might be able to somehow help with your gas cap problem too (ahem).

Tom

[content22207]

Just detune the car to pass the test, then readvance the timing after you get home. Surely you can borrow a gas cap from someone for the test (it's a standard size). Once you have your certification, put the car back the way it was.

Bill Robertson
#5939

[TTait]

I might be able to somehow help with your gas cap problem too (ahem).

Tom

Surely you can borrow a gas cap from someone

But who? (ahem)

[Bitsyncmaster]

I just failed by SMOG inspection due to a combination of a bad gas cap and a too high NOx value at the 25 MPH test. I was told the NOx are supposed to decrease with a higher C/O mixture. Has anybody adjusted this themselves? I know you are supposed to use a wideband O2 sensor, but can you do it manually? Josh Bengston said the value should be at 14.7.

Your standard narrow band O2 sensor should be holding 14.7 if your Lambda system is working and adjusted properly. Have you adjusted the mixture with a dwell?

[Chris 16409]

Your standard narrow band O2 sensor should be holding 14.7 if your Lambda system is working and adjusted properly. Have you adjusted the mixture with a dwell?

No, I don't have a dwell meter. Here's my SMOG report as well.

[Bitsyncmaster]

I can't believe they check ignition timing. Why should they care as long as the smog readings are in?

You look good a lower RPM and it does show your lower with CO at the higher RPM so your mixture must be lean. You need to see if your FV dwell is working properly.

Also the tank pressure test is not only the cap. If your pump boot is not tight you would leak the pressure. You can get a better seal on the boot by clamping just the pump boot and not the pump cover. They can't see the pump cover is not clamped

You may also want to verify your mechanical advance is working. I think it should have full advance at 2500 RPM.