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If you load a new map or do something simple to your stock map like switch of the lambda sensor, you may find you need to adjust the CO trim for a smoother idle or less smelly idle (too much fuel).
To do this with GuzzDiag, get your engine up to temperature (which is 60 deg celsius). Go for a short ride or let it idle with GuzziDiag connected so you can monitor the engine temp.
Once up to 60C, hit the kill switch. Click on 'View' -> 'CO Trim'
You will get the following dialog box. Click 'OK'
You will then be presented with the CO trim menu. Click 'Start'
You will get a dialog box that asks you to start your engine. Click 'Ok' and start 'er up.
With the engine running, click the plus '+' or 'minus '-' button to adjust the CO trim. You can go up to +128 or down to -128.
What value you use will depend on what type of map you have installed and what you are trying to achieve. If you have a map built specifically for the exhaust you have, you should only need to go +/- a small amount. If you smell unburnt fuel, try going to -5. Click 'Finish'. Let it idle for a few seconds. Better or worse? Go up or down as needed. With each change, make sure you click 'Finish'. If you have a rough or lumpy idle, try going positive first. Say, +3 or +5. Better or worse? Go up or down as needed. If you have to go more than 10 in either direction (as a rough guide), you may have the wrong map, or you have a mechanical issue you should address (TB balance or valves), or have forgotten to reset the TPS or autolearning parameters.
When you click 'Start' to make another adjustment, GuzziDiag will ask you start your engine again, but as it is already running, simply click 'OK' and go. Repeat as necessary until idle is smooth and at your required idle RPM. Always make sure you hit the 'Finish' button when you've made a change. Once done, hit the kill switch.
Try not to let the engine get too hot. You can't hurt anything by adjusting the CO trim, so if you feel you haven't quite got it right, let the engine cool off and start again. Of course, you can use a fan to assist with cooling.