Pass CA Smog or Bust - Need Help Please

[SanDiego928]

I tried to pass the CA smog test myself this time around but failed. I previously (2.5 years ago) had the local Porsche shop do it last time. Took him 10 tries and finally passed by changing the set up of the AFM until it passed. He was nice to charge me only for the smog tests and not his time.

Last year I replaced the CAT with a new one from 928 intl.

New plugs, wires, cap and rotor last month from Roger.

Last smog test replaced the oxy. sensor.

Spent over 1,000 bucks on parts and would really appreciate help getting this to pass. I would hate to sell as a parts car. I have been working on my 928 for 6 years now. Thanks so much.

The 'smog only' AFM is a little hard to bolt on, seems like it could be from a different year. It does have a slightly different flange inside below the air filter.


Here is the info. from the fail with the original AFM.



Here is the info. from the fail with the smog only AFM from the shop.

[harborman]

I feel for you guys having to go through all that. No smog tests here in Michigan. Here is an idea. why not go to another smog station some place else next time?

[honerboys]

check your ignition timing, EGR valve and lines, vacuum leaks, not sure if there's a mixture adjustment on that year (too lean) - maybe some one else will chime in - if the settings on the afm have been changed can be a PITA to get them right without an exhaust analyzer - over all it looks to me that your running too lean - now what's the cause..? - check the above

[Plexus928]

25% ethanol mix . it will lowers your emissions by heaps. drain your tank afterwards.

[Mal81]

Been there, done that on CA smog. It was a tough battle, but I did get a pass at the end, so don't give up.

I disagree about using ethanol. Many of us use premium with Techron, but before the test (having cleaned your fuel system and EGR as others have said) run the premium out of the system and refill with Low Octaine fuel and run on it until you are confident that all the Premium is gone. I know it's counter intuitive, but you need to cool your exhaust to get those NOx numbers moving down. Also, again,it seems counter-intuitive, but your new Cat may be contributing to your poor NOx numbers.

[Danglerb]

Factory cat cleans up a world of hurt, but as I recall early cats don't do that much for high NO like more modern cats can.

My two guesses, mismatched injector flow and/or vacuum leaks. NO generally means lean, not necessarily lean in all cylinders, could be just one. The 928 fires all the injectors at the same time and for the same duration. If you don't have a set with matched flow rates some cylinders will be rich and some will be lean. Also if the injectors have never been cleaned they will have plenty of vacuum leaks from the old seals, and vacuum leaks add unmetered air pushing the mix lean.

Smog or not, pay your fees on time.

I would send off 10 injectors and get them to make the best matched set of 8 after cleaning.

[GabrielS]

Luckily my 84 928 has passed CA smog consistently, which only has 42k miles on the clock. Unfortunately my other vehicle, a 85 Mazda RX-7, hasn't faired so well in recent years. It had always passed smog until four years ago, that's when the problems began due to the peculiarities of the rotary exhaust. Replaced the entire exhaust system including the three cats plus O2 sensor. Then found out an air control valve in the exhaust system wasn't functioning correctly thereby keeping the cats from operating as they should. Turned out the diaphragms within the acv were hard as a rock due to the high heat and close proximity to the exhaust manifold keeping them from doing its thing. This was rectified by placing a heat shield under the acv and replacing the acv entirely, it now passes smog but what a PITA it was. Perhaps in the case of the 928 similar components could be affecting the smog output like some of the engine management sensors.

[Plexus928]

quote " peculiarities of the rotary exhaust"
The peculiarities of the engine is the usual problem with rotaries

Too much hysteria out there re Ethanol, but one of the positives is it's totally emission free, the more you have mixed in there with petrol , the lower the readings.
Australia has similar controls to California, had a TR8 fail( badly) 3/1 ethanol mix (with no other adjustments) pass. only noticeable by the alcohol smell, and that's not what the test is measuring.
If you are still using 30 year old fuel hoses it could rot these out, but not overnight. if you have newish hoses (ethanol resistant) just top your tank up and run it out.
We can buy 80% pump ethanol, no newer performance car should be without it, particularly turbos. you do need a dedicated tune to run 80% you will not have to re-tune with a 25% mix. It's a bit too high a percentage for daily running, your performance will be a tad sluggish but it will get you through the test.
10% is a good mix, My beast never uses anything else.

[SanDiego928]

Originally Posted by Danglerb

Factory cat cleans up a world of hurt, but as I recall early cats don't do that much for high NO like more modern cats can.

My two guesses, mismatched injector flow and/or vacuum leaks. NO generally means lean, not necessarily lean in all cylinders, could be just one. The 928 fires all the injectors at the same time and for the same duration. If you don't have a set with matched flow rates some cylinders will be rich and some will be lean. Also if the injectors have never been cleaned they will have plenty of vacuum leaks from the old seals, and vacuum leaks add unmetered air pushing the mix lean.

Smog or not, pay your fees on time.

I would send off 10 injectors and get them to make the best matched set of 8 after cleaning.

Thanks Mike, I may have to go after the injectors. Money is getting thin on this hobby though.

Thanks for all the others input too.

I found I had # 3 plug wire loose when I went out to drive her around the block the other day. It was very hard to start and I could tell it was missing when I started her cold. I did not notice that after the test when I came home. I ensured # 3 is on correctly now.

Could that have been part of the NO issue?

I maybe able to get another go at the test station.

I really need to get this under control or I may have to part with her and as we all know these early ones are not an expensive Porsche to buy, just to own.

Mark

[Danglerb]

I've bought a few motors for parts and when I checked the spark plug wires a good 20% or so had parts that seemed to work but measured bad. Overall I don't think I ended up keeping more than about half, just the ones that measured good and also looked free of damage.

When I first swapped the motor from my 84 Euro parts car to the 85 Euro I was too stupid to make a parts car I did a full pro $$$ carbon clean on the injectors. It barely passed smog, then failed on the next round, so I pulled the injectors and sent them out for cleaning to the guy that was cheap in San Benardino. Most of my issues I think were from leaky old seals, which I could have bought and changed myself, but two of the injectors were too far out of spec, one of them like 20% down (good thing I sent a couple extra injectors, but could have been the extra's that were bad, no telling.)

Short answer, new seals and clean injectors and you don't have to worry about the problem being injectors for a few years. Cars that can't pass smog can be trouble to sell in Calif beyond much lower selling price. If you have to do that register it as non op first.

[Fast Freddy 944]

Originally Posted by SanDiego928

I tried to pass the CA smog test myself this time around but failed. I previously (2.5 years ago) had the local Porsche shop do it last time. Took him 10 tries and finally passed by changing the set up of the AFM until it passed. He was nice to charge me only for the smog tests and not his time.

Last year I replaced the CAT with a new one from 928 intl.

New plugs, wires, cap and rotor last month from Roger.

Last smog test replaced the oxy. sensor.

Spent over 1,000 bucks on parts and would really appreciate help getting this to pass. I would hate to sell as a parts car. I have been working on my 928 for 6 years now. Thanks so much.

The 'smog only' AFM is a little hard to bolt on, seems like it could be from a different year. It does have a slightly different flange inside below the air filter.


Here is the info. from the fail with the original AFM.



Here is the info. from the fail with the smog only AFM from the shop.

If you love your hobby, I hate to say it, you may have to move to a different state......

[Danglerb]

Even in another state if it won't pass smog its not running well.

[curtisr]

While addressing the problem and fixing it right is always the best route I wonder what Guaranteed to Pass would do for you. They purport to deliver the following:


FEATURES

• CRC Guaranteed To Pass Emissions Test Formula is a powerful detergent with additives that will super-clean your entire fuel system, reducing emissions and improving performance
• Lowers CO, HC, and NOx emissions to guarantee a passing emissions test
• CRC Guaranteed To Pass removes harmful gums and varnish from carburetor and emission control components
• Cleans intake valves, injectors, and combustion chamber
• Recommended for use every 4000 km to improve fuel economy, acceleration, airflow, and reduce emissions
• Works with all gasoline and ethanol-blended fuels

[Danglerb]

Originally Posted by curtisr

While addressing the problem and fixing it right is always the best route I wonder what Guaranteed to Pass would do for you. They purport to deliver the following:


FEATURES

• CRC Guaranteed To Pass Emissions Test Formula is a powerful detergent with additives that will super-clean your entire fuel system, reducing emissions and improving performance
• Lowers CO, HC, and NOx emissions to guarantee a passing emissions test
• CRC Guaranteed To Pass removes harmful gums and varnish from carburetor and emission control components
• Cleans intake valves, injectors, and combustion chamber
• Recommended for use every 4000 km to improve fuel economy, acceleration, airflow, and reduce emissions
• Works with all gasoline and ethanol-blended fuels

Wrong part of the label, read the details of the guarantee, the conditions for them paying etc.

IMHO its pure snake oil with no real effects.

[tmpusfugit]

Full agreement here. Snake oil. It does have one real effect, it puts a dent in your wallet....

[MPDano]

I would change out the Cat, Mark. Does yours have a air tube on the side of the cat?

[MPDano]

Oops, just saw you have a new cat. Ditto on the injectors rebuild. I sent mine out to Witchhunter and they come back looking new and with a flow match printout.

Also, verify your smog pump is working, need air to your cat to burn those emissions. Those also have an air filter next to them.

[v2rocket_aka944]

either your cat is shot, or you are running lean.

the very low HC/CO numbers make me think it is the latter. the O2% being 3-4% on the tests posted also shows a lean mixture...it should be 0-1%.

HC/CO vs NOx tend to be inversely proportional, one goes up, one goes down.

your CO2 % of 11-12 is low - CO2% is an indicator of "combustion efficiency" and ideally should be 14-15%.

how old is the coolant temperature sensor?

[SanDiego928]

Thanks everyone. I had open heart surgery and will re-visit my 928 at a later time.

[honerboys]

wow - get better soon