Dreaded California smog check

[mwredit]

Took the HPE to get it smogged this morning.  Well, to my disappointment, it failed due to high CO readings (measured 2.75, Max is 1.46, normal .17).  Everything else was low, like the NOx was below average and the HC was slightly above average.  It seems like the carb is running too rich.  The smog guy said to junk the car (I DONT think so, it's rust free!) and didnt seem too knowledgeable about carbs.  It has a 32 DATRA 12 Weber.  I rebuilt this carb a few months back with a new carb kit and float.  Perhaps the float level is too high?  If it had a power valve, I would suspect that.  I cant imagine it being more than the float setting.  It has been spatting at the mid revs once in a while, the few times I've been driving it.  This car passed smog two years ago and everything passed then.

Thoughts?

Thanks,
Mike

[dougdee123]

Hi ,

The float level is really not the issue. All that does is stop the the float chamber overfilling.

What you need is someone to adjust the mixture.

http://www.lancisti.net/forum/content.php?2-DMTR-DATR-DATRA-carb-adjustment-guide may help.

Doug

[capriblu]

As first step -  Take the car for a good old "Italian Tune-Up".  Then adjust the idle mixture via the screw (on rear base of carb body on opposite side to throttle linkage/choke).  Turn slowly in (clockwise) until revs just start to drop or roughness in tickover starts to be felt. Then slowly turn out (anti-clockwise) just enough for smooth tickover to return.   Retest CO.   If this yields the improvement needed for test then open out a little more (2/3 a turn).   

[mangocrazy]

What engine revs is the smog test performed at? If it's at idle, then I'd echo what capriblu says. If the test is performed off idle, then you may need to change one or other of the jets. A bad person would run it lean to get through the test, then put it back to 'normal' afterwards. I couldn't possibly condone an action like that, of course... 

[mwredit]

That's what I was told by Mark Allison, a local Fiat guy, to use a larger primary air jet and a smaller primary low speed jet.  Apparently, California tightens up on their requirements every 6 months, so it makes it harder and harder to pass.  Mark told me that my CO readings looked normal for my car.  Here's the readings I got yesterday-

                         HC                                       CO                                     NOx

                MAX    AVE   MEAS                MAX   AVE   MEAS                MAX    AVE   MEAS
15mph       232       40       59                  1.46     .17     2.75              1434    520     344
25mph       200       31       49                  1.26     .15     2.58              1294    452     291

This was done at around 2100-2500 rpm.

Looks like I'm looking at jets now.

[mwredit]

To make a long story short, my HPE finally passed Calif smog last week.  The secret is that I had to change out the idle air jet for the primary side to a bigger size for the test.  I used one that was drilled out.  This brought the CO% down.  However, the air injector rail that attaches to the head was 3/4 plugged, which had added to the problem.