Re: Is this the correct way to adjust the CO when you are poor? (tolusina)
| Quote, originally posted by tolusina » |
George,
That will actually work reasonably well on CIS cars. A better method is to combine what you've described with a dwell or duty cycle meter and you can make CIS cars absolutely purr, best performance, fuel economy and emissions.
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I'd beg to differ with the use of the dewll meter. According to the Bentley it is used to verify settings and switch operation, NOT to adjust the system. (Bentley pages 6-12, 6-13, 5-30, 5-31) At no time is it suggested to set the mixture according to the reading on the dwell meter.
Trying to adjust the mixture with the O2 sensor plugged in means every adjustment you make will be "fought" and offset by the computer.
The correct procedure (as posted in the FAQ's) is below.
0. Ideally you should pull the injectors and run the fuel pump. While the pump is running adjust the air flow plate with the 3mm Allen wrench (clockwise/rich) until the injector starts to leak. Back off until it stops. This sets you to the very rich side of your adjustment scale without having the injectors leak on you. This step can be skipped if you're very sure you are on the rich side of the adjustment range. Reinstall the injectors. Put everything back to normal.
1. Warm up the engine until the fan has run twice.
2. Begin adjusting the airplate a 1/16th of a turn counterclockwise at a time. This is slowly leaning out the mixture. At some point (and it may be a while) the idle will start to drop. If not sure blip the throttle a small bit to restablish an idle point. When you believe you've seen the idle drop then adjust in the opposite direction (clockwise) to richen the mixture. The idle should now rise. Repeat the adjustment to verify that you are at the "Lean Idle Drop" (offical phrase). Set to just a bit richer than the drop point. That will have you set about as accurately as you can get without acutally using a tail pipe sniffer to verify it.
3. Remove the friggin' Allen wrench. It won't hurt anything but it'll reduce your rev range when the wrench hits the hood and won't rise anymore (Don't ask how I know this.)
4. There is no step 4.
The O2 sensor on a Lamda system will compensate for any changes you make with the airflow plate which is why it should be disconnected on a Lambda system. The O2 sensor changes the duty cycle of the frequency valve to adjust fuel pressure to the injectors and therefore the "richness" of the mixture.
A bad O2 sensor will throw off the mixture severely. Disconnecting the O2 sensor will only return your CIS to exactly what it was when Bosch first designed it. Before emissions and gas mileage was a huge concern. Many disconnect it so it doesn't mess with their settings. To adust the airflow plate rich or lean affects the entire airflow/rev range. So a" richer" setting here means richer thruout the powerband. Ditto with lean settings.
Anytime you change system pressure through a new pump install, filter change, injectors, fuel distributor etc. the mixture adjustment should be repeated. Since you'll be almost perfect to start with it won't take much adjustment.
Had to jump in because the use of the dwell meter is a VW "urban myth".
