Failed Smog
 

A bit of a rampage here. Just got my semi-annual smog today, and of course failed. What is curious is that two years ago it passed with flying colors. I know, I know, everybody says 'nothing has been done', but all I've done is changed the DME relay and change the oil.

So, here goes. What could make the the HC gone from 77 to 181 and the CO(%) goe from .56 to 2.67. The CAT and Oxygen Sensor were changed about 3 years ago, but could be bad I guess. The testing guru said that it was running rich and to get it that high he would have to be pouring gas straight into the intake.

I didn't think you could changed the fuel/air mixture on an '84 3.2, but he displayed his wisdom by suggesting that my 'performance tuner' had made it rich to run better. I guesss he assumed that everybody with a Porsche has a performance tuner.

The car runs great and only has a bit of a problem with starting hard once in a while.
Any ideas anybody?
Thanks.
John

Just three months ago I had my car smogged, but first I took it to my mechanic and he 'de-tuned" it or adjusted the CO% level so that it ran very lean (1% or so). Performance sucked, but it passed smog no problem. After it passed, I took my car back to him and he adjusted the CO% up to around 2.5% - where it should be. It cost me $65, but it was worth it.

John your air/fuel mixture can be adjusted. It is on the air flow meter. There is a small hole that you put an allen wrench
into. 3mm I believe it is a verticle opening on the front left corner on the bottom. From the factory I think it has a cover over it but it is usually removed and left out.

Your best bet is to find a mechanic that can get it set to pass and then readjust afterward unless you have access to a tester of some kind.

The shop I use here gets it passed for me as well.

That's a huge jump in HC & CO output. Was the car thoroughly warmed up? Get out on the open road and dog it before the next test. However, if you do find there are smog related repair needs, keep us informed.

Car was thoroughly warmed, as well as the temps being in the 90's today. I had driven it about 25 miles before the test. I'm going to change the oil and air filter again then see what happens.

Snipernick: might be worth the $65 extra.
Thanks all
John

Guys guys guys, he has an 84. that means it is not CIS so he can't change the mixture with a 3mm allen wrench.

You have a problem with your fuel injection. One of your sensors is sending a bad signal or no signal at all to the computer brain.
The system needs to be checked and the offending culprit fixed or replaced. The O2 sensor is my guess but that's just a hunch.

Hmm, I thought 84 being the first year of the carrera has the motronic thru 86 with slight change in dme in 87. My 86 should have the same thing as his 84 hence the 3mm.

Sammyg, you sure about that?

That's what I think it is, too.

You have been brainwashed by your ignorant mechanic. 1% before the CAT is not "very lean". 2.5% is rich. You should be able to run perfectly fine between 1 and 2% CO.
BTW, how did you measure the performance at idle?

Sammy's got the best advice for the original problem. It could also be a dirty injector, although the HC numbers would have gone up quite a bit more if so.

With older rides, it's best to pretest before trying to get a smog cert.

I consider an O2 sensor a wear item, like brake pads, except ya can't look to see if it's working.....best to consider it dead....run a bottle of techron thru the tank and re-test with the new sensor....THEN go to the smog weenie.

dvkk -

I feel compelled to defend the mechanic that adjusted the air/fuel mixture on my car. He's one of the best in the business. No advertising but a humble phone book listing and he has more business and more Porsches lined up outside his shop because he's damn good at what he does. Anyway, since I am not well versed in CIS, I'm probably leaving out key details. One detail I did not post is that my car would have passed smog the first time if it weren't for the high idle (1000-1100 RPM). I didn't want to mess with it, so I took it to somebody who knows CIS. My mechanic adjusted the idle and using a gas analyzer adjusted the air/fuel mixture so that it would pass for sure. It ran extremely lean, but passed smog of course. Then, I drove it back to my mechanic and he set the mixture back to where it should be. Runs like a rocket. jbirkett is under a time constraint to pass smog. There's no time to fart around. Take it to somebody who you trust and and has the knowledge; you'll save yourself time and money. Pass smog, then install that cat by-pass pipe you've always wanted! ;)

Answer: a bad head temp sensor.

Question: do you still have the single wire sensor?

Joe

Although your mechanic may be very good at most every aspect of the cars, I still contend that any mechanic that refers to 1% CO as "very lean", and 2.5% where it should be, doesn't know his numbers. Your smog authorities do know their numbers, that's why they set the limits to fail such rich A/F ratios.

Get a 1973 911! Smog exempted

How low are the smog numbers going to get before we rebel? They keep dropping them with the intentions of getting ALL older cars off of the road.
They care so much about the lowest income people that they will show them-they'll take their car away!
You know the difference between a statesman and a politician? The statesman does whatever is right, no matter the cost to himself. The politician does whatever is right for himself, no matter the cost to everyone else!
Drums

The smog numbers are the same as when they were first sold....no changes.

The issue is the manufacturers making replacment smog equipment..... ever try to source parts for a 76 912E.....?

Yeah, I guess the only changes that were made were every 2 years putting them on a dyno and that they are supposed to burn as new.....no changes....