Howell, Again

[Rob O]

Did you check for a crossed o2 sensor by actually swapping sides, either
at the ECU end or the sensor end, and running it?

Just a thought... maybe not a brilliant one but like all free advice
worth every penny you paid for it :)

Rob_O

Onebil2mny at aol.com wrote:
> 
> OK boys and girls, this is where we have gotten. We installed the new
> computer and it fired up fine. A little hesitation at first, but that went
> away. I assume this is because the new computer had to learn. Anyway, the
> first 100 miles or so went fine, and I thought we had it licked. I thought
> wrong. Here are the symptoms, and what I have checked.
> 
> You may recall that this is an LT-4 Corvette motor installed in a 1956
> Chevrolet. The computer (18188021) and harness was purchased from Howell
> Engineering. The computer is set up as a speed density system, and uses the
> following sensors.
> 
>     MAP sensor
>     MAT sensor
>     Cam sensor (I assume) from the distributor
>     (2) O2 sensors (4 wire)
>     (2) Knock sensors (common wire)
>     TPS sensor
>     Coolant Temp. sensor
> 
> The problem is that sometimes, usually during "warm up" as the vehicle goes
> into closed loop, the computer will drive one bank so rich as to blow black
> smoke from that side of the exhaust. Although it hasn't acted up on the scan
> tool recently, the last time it did, the O2 readings were high, while the
> pulse width was wide, indicating that the computer was driving that bank
> rich. It recently acted up, and set a left side lean exhaust code (44) but I
> do not know which side was running rich at that time.
> 
> I have checked for crossed O2 harnesses and they check out. I got a print out
> of the pin voltages, and did the requisite checks on the O2 sensors and
> everything checks OK, zero volts on the "low" side of the O2 sensor, etc. The
> low side does read around 1.5v on the harness side when the sensor is
> disconnected, but I see no specification for a disconnected sensor. While my
> next step is to start checking ECM grounds, I am hoping that someone else
> will have another idea. I am certain the ECM is grounded, and grounded well,
> but I am going to check just to be certain.
> 
> Thanks for any input you can send me...  This thing is starting to... erm...
> well, I'm not real happy with it, that's for certain!
> 
> Shiny Side Up!
> Bill K
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