Quote:
Originally Posted by Dave Colangelo
It sounds like you need to get a proper wideband and adjust your mixture.
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Without an O2 sensor, I agree. Duty cycle will be controlled by sensors and switches. There will be no input from the O2 sensor to allow tweaking with a dwell meter.
If there are no air leaks there are two main culprits for the rich running. control pressure/CO adjustment.
Your control pressure must be checked with gauges. Your CO can be tweaked manually without an analyzer but if it was set rich previously to make up for other problems that have not been repaired, you are pissing in the wind if you expect to be satisfied with the results. This means you can turn the 3mm screw and lean out the richness and the other gremlins will surface that have been drowned out by fuel.
Here is my recommendation for a task list.
1. When the engine is fairly cool and running spray carb cleaner on air connections/injector seals/intake runner gaskets and search for leaks. Listen for a change in engine RPM. Spray the airbox on the outside as well. Use the red straw with the can and there is no need to douse anything. A spritz will do. Repair air leaks.
2. Spring the buck and a quarter for CIS pressure gauges and test your control pressures. Many threads on adjusting cold control pressure and a few on tweaking warm. Get the numbers and report. I can find you the pressure graphs easily enough if you want to do this. Lots of help here regarding adjustment.
3A. Is there a test bung on your exhaust system? If so, spring for the analyzer or pay someone to set your CO. I don't know if you can just stick a sniffer in your muffler and have that be adequate.
3B. Set your CO "manually" with the help of this link. With some patience you can get it way better than it is now.
http://forums.pelicanparts.com/porsche-911-technical-forum/232089-cis-idle-speed-mixture-setting-without-analyzer.html