View Single Post
Old 09-09-2001, 11:16 AM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Boy did Larry hit it. I have only seen a couple CA cars and for years I ignored the lack of intergrator values and used only the EHA current method.

A few years ago I found that if you prepared the controller properly one could get the integrator value at the X11 with on-off ratio as the Federal cars do. I think the proceedure might be to energize the fault code sequence at the X11/4 connector.

When doing the EHA current test and adjustment a couple things should be noted. Current during cranking can be as high as 70ma when combined with the current used for cold running. All forms of current control should stop within less than a minute, probably about twenty seconds. After all starting and cold running enrichment is gone the nominal value of zero ma (milliamps) will proceed till the O2 sensor activity is recognized. An important system check can be to disconnect the green O2 sensor lead under the pass carpet and verify that zero ma is nominal value with engine warm.

O2 sensor control (closed loop - lambda control) has the ability to increase fuel mixture (+ma) by about 12ma. The control can subtract to -12ma if the natural mixture is too rich. The idea is to get the system in closed loop control with its base mixture such that the elctronic system has equal ability to control rich/lean; at zero.

The real value to adjusting mixture this way is that feedback control is also monitored (actually all electronic control is monitored as this IS the way all electronic control is affected). If you are stuck at either end -12ma or +12ma you will have to correct the mixture untill the value moves. If it won't move verify zero ma with O2 sensor disconnected. If the system has been rich for too long the O2 sensor will be fouled. I often disconnect the O2 sensor set the mixture to best running (moved from lean to rich) and drive it around the block to clear the sensor. Reconnect and try again.

Once the system starts to follow the mixture it should eventually gain closed loop. This means that the ma value is seen to go rich, stall, go lean, stall, go rich , stall, go lean etc. etc. This will take place very much faster with the added heat of 2000rpms. It also should center around the same relative mixture position (4ma is a lean condition, -3ma is a rich condition) whether at 2000rpm or at idle - just the speed of transition will be much greater at the faster speed). Setting the mixture to zero means setting the fuel distributor to the mixture that gives the average position of closed loop control is at zero. The ma values will swing one to two ma both sides of zero (remember average - a constant ma will mean you are not in closed loop).

BTW although zero is the preferred book value, I always set my cars to about 3-4 ma negative (rich). While this makes no difference to warm, steady state, closed loop, mixture. It does leave a rich bias to all non closed loop states such as full throttle, rapid acceleration, and cold operation.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
Reply With Quote