Emissions/Lambda

turk911 · 09-08-2003, 03:59 PM

Hi, I am having problems getting my 1983 911 SC to pass smog. This car has a good history of running good and always being able to pass the stringent emissions here in Southern California.

The car runs very well with the O2 sensor disconnected, and feel it may even pass by leaning out the the mixture and leaving the O2 sensor disconnected.

With the O2 sensor connected it is running rich, it pulses at idle, it blows out black smoke when reved, and sluggish throttle response. If I attempt to lean the mixture screw (CCW) it just gets worse which seams to be overly rich condition. How is this happening?

I've checked the lambda system throughly in the following manner:

With digital duty cycle meter connected to the test port, grounding the O2 input lead causes the indacator to drop (associated with the frequency valve to also change audible pitch). Conversly connecting a 1.5 volt battery causes a change in the opposite direction on both the meter and frequency valve pitch. This seams to indacate that the lambda computer is working correctly.

Also I have checked all power , grounds, and switch input signals to the computer and enrichment module and relay. All were OK. What is the enrichment module for? Do these go bad? I opened it up and found NO obvious damage(burnt resistors...)

I,m starting to loose sleep over this. I appreciate any suggestions.

TIA
Michael Sirolli

Tyson Schmidt · 09-08-2003, 10:44 PM

This might seem overly simplistic, but have you tried a new oxygen sensor?

Jim Smolka · 09-09-2003, 03:18 AM

With the engine cold, measure the resistance of the of the signal wire to ground. Should be very high resistance. (I think SC's had only one wire O2 sensors). With the car running and hot, disconnect the O2 sensor wire and measure the voltage comming out. Should be around 0.7 VDC.

Dan Owens · 09-09-2003, 06:20 AM

I'm with Tyson, replace the O2 sensor and then have the air mixture adjusted properly.

Superman · 09-09-2003, 06:28 AM

Or just disconnect the darned thing and have someone set your mixture really lean. Pass emissions. Richen mixture. Smile and drive.

Eugene at Pelican Parts · 09-09-2003, 07:50 AM

Exactly which emission are you exceeding? That may offer some profound clues.

Somehow my SC passed CA smog easily, and I have no smog pump, a disconnected EGR, and a leaky CIS. Go figure.

turk911 · 09-09-2003, 01:58 PM

Thanks all. I 've put in a new O2 sensor. With the sensor removed I can set the mixture with a Gunson to .5% CO and it runs very smooth. Then reconnecting the sensor causes RPM to oscillate.
turk

Dan Owens · 09-10-2003, 05:42 AM

There's really no point in putting in a new sensor and then disconnecting it to set the mixture is there? I'd try connecting it and then set the mixture so that the system does what it's suppose to do.

turk911 · 09-10-2003, 07:56 AM

DanO setting the mixture with O2 sensor disconnected is the proper proceedure IAW Porsche.

Can I retard or advance the ignition slightly just to help?

Does anyone know of a off the shelf smog pass fuel additive that wil help?

I have one more shot at this before I go the ... other ... route!

dandrews64 · 12-10-2005, 12:39 PM

Resurrecting old thread.

There is a duty cycle test port referred to here.

Where is it??

1982 911SC.

(I'm testing control pressures and want to set CO's using the dwell meter cheat).

Thanks !!

Boxer 6 · 12-10-2005, 10:12 PM

Man, you guys got it tough in California. I'm installing a set of European Racing Headers into a pair of racing muffs on my 87. Think I'll make it through inspection? I don't really care! I ain't going anymore! I'd rather have the ticket.

dandrews64 · 12-11-2005, 06:09 PM

Bump

Where is the Duty Cycle Test Port on an '82 911 SC ?