adjusting engine rich/lean

[syljay at optonline.net]

>From: William Magliocco <magliocc at rocketmail.com>>
>Does the engine have a good O2 sensor (if it has one>at all, I am not familiar with the Euro specimens)?
>If so, you should be able to rough it in with a
>digital volt meter on the output of the O2 sensor. 
>You are looking for 0.4 to 0.5 VDC if you are at>stochiometric (14.7:1) ratio.>
>You could also disconnect the black lead of the 02
>sensor; this would put approx. 0.5 VDC on the computer
>input.  Hook the meter up to the O2 lead you just>disconnected and adjust the flow plate for the 0.5VDC level.

***** I also set up the basic idle mixture this way.I disconnect the O2 sensor wire from the harness and attach the voltmeter to the O2 sensor.
I pull the plug on the DPR also as I do not want the computer messing with the mixture. You are basically in limp-home mode at this point. But what the hell, it cant hurt to pull the DPR plug.
Then I set the mixture using the voltmeter. It takes a bit of doing as the adjustment is pretty touchy and the O2 sensor is REAL sensitive at stoichiometric.
You don't have to be dead-nuts accurate here as long as you get the reading in "the window" . . the range within which the computer can make adjustments with the DPR.
I've had a situation where the idle mix setting was just at the edge of the operating window. From a cold start, the system never went into closed loop mode . . .the mix was just too lean and the DPR could not drag it into Stoich. 
However, after a good warmup, the system went into closed loop mode. But, more often than not, the system would go into open loop during idle. At RPM's over 1500, the system would go closed loop.
The fix for the problem was to richen up the mixture just a wee bit.

After the adjustment, you can confirm the setting by measuring DPR current, which should swing around 0 ma as Huw mentioned.
Also test from a cold start. Time how long it takes for the DPR current to  start swinging. I think the time was about 3 minutes for the O2 sensor to get hot enough to start working.

Syl in NJ