I've got an 86 944 that has 54,000 miles. The car is having a hard time passing smog. Im located in California. I had the car tested and it was high on the HC and CO at both 15 and 25 mph. The NO was fine. When I started inspecting the car, I found that the timing belt teeth were broken off so the timing had slipped quite a bit. I ended up replacing the timing belts and setting the timing back to normal. The car has new spark plugs, a new o2 sensor, and a new cat. I took it back to get smogged and I had the exact same results (high on HC/CO and low on NO). The gas in the tank was a bit old. What do you guys suggest I try?

 

High hydorcarbons means there is fuel that is not getting burned. The car is running rich. Might want to try an adjustable fuel pressure regulator. It is low on Oxides of Nitorgen because of the fuel not getting burned. When all of the fuel is burned creates high Oxides of Nitrogen. I Put a Lindsey Racing Mass Air Flow sensor on my car and I can ajust the fuel to air ratio

 

There is a provision (944 and 911) to make small adjustments to the fuel mixture (injection pulsewidth) and the ignition timing in order to compensate for the quality of fuel available in your particular country or region.

There is an board-mounted eight-position rotary switch accessed through the little hole in the back side of the DME box. These adjustments can be made without opening the cover of the DME box, unless you have a California vehicle, which will probably have a metal plug over the hole instead of a plastic fitting. The switch has a triangular-shaped recess i— I just whittle down a golf tee to make mine.

The switch has detent positions so you can count the clicks to tell where you are set. All the DME boxes I’ve ever seen have been set on position #1, so I call that the stock position. The adjustments can be found in the following table:

switch position/fuel mixture adjustment/ignition timing adjustment

1 stock 0/0 degrees
2 +3%/0 degrees
3 +6%/0 degrees
4 -3%/0 degrees
5 0/-3 degrees
6 +3%/-3 degrees
7 +6%/-3 degrees
8 -3%/-3 degrees

Try using position 3! to give it less gas,
and take youre car HOT not cold to the emissions. this will help for the CO.

Hydrocarbons: this class is made up of unburned or partially burned fuel,.
Nitrogen oxides (NOx): These are generated when nitrogen in the air reacts with oxygen under the high temperature and pressure conditions inside the engine. .
Carbon monoxide (CO): a product of incomplete combustion, carbon monoxide

My car 86 Porsche 944 was failing all 3 test and I used the position 8 and it pass emmsions OK! Changing the timing back helped pas NOx test because of colder combustions but that is not youre problem so use position 4..


http://en.wikipedia.org/wiki/Automob...ssions_control
http://www.pca.org/tech/tech_qa_question.asp?id={6F4C6FD1-D3DD-459F-B186-53B73A8E0C60}

 

Use Position 4!

 

You might try replacing the DME temp sensor. It is probably the original. They tend to run rich with age.

There is also a CO adjustment on the AFM.