280 SE failed CA smog

[Feather535]

Well the fun continues with the 280 SE I rescued a while ago.  It runs and drives surprisingly well and everything works except the climate control and cruise control...except that it failed the California smog test.  It's pretty far off, too: CO registered at 6% at the test station--gross polluter territory. 

I've been able to get it down to about 4% with the mixture screw, but it needs to be about 1% to pass. 

There is fresh fuel in the tank, the car has been driven less than 100 miles since the oil was changed, control pressure and system pressure are correct, and the idle speed and timing are within spec.  What else to check?  Could the catalysts be bad? 

[SuitGuy]

I'm not super familliar with CA emmissions, but catalytic converters wear out with age (~10 yrs).  Do you notice a sulfur-y smell from your exhaust or a decrease in engine performance? Those point towards a bad cat. Could your exhaust be leaking?

[ramiro]

Why can't you get it down more by adjusting the mixture screw , even without a cat the manual calls for 1% at idle so your car clearly runs to rich at idle so you should adjust the mixture screw more.

The only weird thing that a cat engine the manual lists that CO should be lower then 2.5 % instead of 1 % for non cat but still 6% is to rich in any case .

Even my 6.9 got 0.3 % without cat at idle.

[rumb]

Found this good article
https://mechanics.stackexchange.com/questions/42495/what-could-cause-high-hc-and-co-but-low-no-and-co2-in-a-smog-test

[Feather535]

Why can't you get it down more by adjusting the mixture screw

That's the question!  As I lean out the mixture, the idle speed drops, eventually so much that the idle air screw can't compensate anymore and the engine stalls. 

I'll just add that all the original smog equipment, including the air pump and the dual cats are there, but I have no idea if they are working now or when the car was parked 10 years ago.

[ramiro]

 Did you measure the co while you adjusted the mixture screw ?

[Feather535]

Did you measure the co while you adjusted the mixture screw ?

Yes.  Got it down to about 3%, but that's not good enough.

[Frankthemoneyman]

I feel your pain Feather535, the old gas engines are getting harder and harder to smog, California silent way of pushing old cars out. If you owned an older car in California for a longer time, you will also notice that the emission limits have been getting lower over time.
Are you just attempting to get your initial smog, to get the car into your name or are your long terms plans to smog the car every two years ?
Please feel free to IM me.

[Alec300SD]

If you haven't done so, replenishing the rubber air intake hoses, vacuum lines, fresh spark plugs, fresh air filter, and also cleaning the throttle body (so the butterfly vave operates smoothly), might help you get  below the 1% CO range required to pass the smog inspection.

[ramiro]

Did you check the ignition timing , i find it weird that you are not able to compensate the idle speed with the idle air screw normally there is plenty of room to increase idle speed.

Is the idle smmoth and running on all cylinders, easy way to diagnose is to put your hand after the exhaust if there is a even stream or if it pops ?

Or maybe the cat filled with unburnt fuel or the rest of it after all the adjustmens with the WUR, did you drive it a longer distance or just short trips after you got it running normal ?

[Feather535]

Did you check the ignition timing

Ramiro, the timing is correct and the car was running well before I started messing with it.  I'm starting the think the mixture adjustment might not be the source of the problem.  Non-functional cats, carbon buildup on the valves, etc, are possibilities. Since this car sat for 10 years, it may just need to be driven.  Problem is that I can't legally drive it on the road until it passes smog.  That sounds like Catch 22 (dated American literary reference).

[Feather535]

replenishing the rubber air intake hoses, vacuum lines, fresh spark plugs, fresh air filter, and also cleaning the throttle body

Changed the air filter, will do spark plugs.  Which rubber hoses and vacuum lines to replace?  There are a lot of them.

[Feather535]

Are you just attempting to get your initial smog

Good to hear from a fellow suffering Californian.  I'm all for clean air, but some of these rules are over the top.  I'm trying to get the first smog so I can register the car.  Where I live a smog certificate is only require on transfer of ownership, so once I'm able to start driving this car, I should be able to sort out any issues.

[Alec300SD]

Changed the air filter, will do spark plugs.  Which rubber hoses and vacuum lines to replace?  There are a lot of them.

Any of the emissions control hoses/vacuum lines that have lost pliabity from age/heat. Check for radial cracks on the inside diameter of the hose/vacuum line ends that are disconnected for inspection. Look closely for external cracks in the disconnected hose/vacuum lines near the point where the nipple connection would end. In particular, any vacuum lines to the distributor and throttle body that are easy to remove need to be replaced.

[Shervinator]

Are you just attempting to get your initial smog

Good to hear from a fellow suffering Californian.  I'm all for clean air, but some of these rules are over the top.  I'm trying to get the first smog so I can register the car.  Where I live a smog certificate is only require on transfer of ownership, so once I'm able to start driving this car, I should be able to sort out any issues.

Only in California does one need to worry about abiding by smog laws for a nearly 50-year-old car. I feel your pain, fellow sufferer.