I strongly suspect that weak cylinder is putting off enough unburned
hydrocarbons that the mean effect is you are out of the range of adjustment
for the system. What is the min spec for compression?? About 102 if memory
serves. You certainly are out of spec for total difference between
cylinders. This creates a situation where the oxy is reading an average of
3 lean cylinders and 1 rich, resulting in the oxy sending false data to the
ECU. The fact that you cannot get open loop below 0.5v verifies the
weakness is beyond the operating parameters of the system.

Now, if your mechanic was aware of the compression imbalance and didn't
recognize that as an issue of high concern, he has not the knowledge to be
servicing Bosch systems. Moreover, if he didn't do a compression test very
early in his analysis, he is incompetent to do diagnostic work. I don't
care if his wall is full of certifications, his actions are definitive in
this regard.

This is why proper procedure requires you verify mechanicals first. If
that's out of spec and you don't know it, you can futz with it till hell
freezes over and never get spec tune. Mechanics who don't follow proper
procedures are a bane to society.

The charcoal hose should be a clear (yellow with age) vinyl hose entering
the motor compartment at the right upper front and running directly to the
upper air filter cover. It fits on a round fitting, about 12mm diameter,
and originally was clamped with a permanent squeeze ear type clamp.

At 06:41 PM 08/24/2002, you wrote:

>Doktor Tim,
>
>The compression is (in cyl order) 130, 128, 132, 98-100 (most likely rings).
>Fuel pressure is good per test I watched the mechanic perform.
>  I couldn't find the Charcoal hose going to my air filter.