CIS tuning

[Nicholas Miller]

I'm not 100% you are going to run correctly with the 02 sensor removed from
the exhaust.  At WOT, you are on closed loop, not refering to the O2, but
if you are part throttling it 'even at high rpms you will be referencing
the O2 sensor, though I am not sure what percentage of throttle it would
change over.

I'm with DeWitt,  I would smoke test it first to find any air leaks.  If,
at wot you are running lean, an unmetered air leak would be a very simple
explanation.  As well, I had a really bad one a long time ago on my 5kqt at
the igloo which was not easy to see visually until you removed it and
checked on the bottom of it.

Good luck,

Nick


On Fri, Jan 22, 2016 at 6:30 PM, DeWitt Harrison <dewitt635 at gmail.com>
wrote:

> On Thu, 21 Jan 2016 15:40:36 -0800 radek at uniserve.com wrote:
> <radek at uniserve.com>
>
> > Hello all surviving CIS fans :)
> >
> > I decided to finally tackle the high idle problem in my winter ride,
> > an 88 90Q.  I borrowed a wide-band O2 gauge, showing actual
> > air-to-fuel ratio.  For now, I just removed the existing O2 sensor,
> > replaced with the gauge's sensor and fired up the car.  First, it was
> > running very rich, until it warmed up.  Once warm, the mix would be
> > around 14:1 at idle, but would get very lean at higher rpms, up to 17:1.
> >
> > Are these results meaningful at all, without O2 sensor connected?
> >
> > The gauge has an output wire that can simulate O2 output to the ECU,
> > which can be set (in low-voltage mode) to between 0 - 1 V.  According
> > to Huw's page, this is the range a regular O2 sensor operates on?
> > Just want to double check, wouldn't want to fry my ECU.
> > Thanks for any input and guidance,
> >
> > Radek.
>
> Provided all the CIS sensors, such as the stock, narrow band O2 sensor,
> temperature sensors, and the essential idle control items such as the idle
> control air valve, air flow meter adjusting screw, etc., are working, just
> follow the factory procedure (Bentley) to properly set the idle control air
> valve duty cycle. To do this easily, you will need a couple of DVMs and a
> made up test cable to put in series with the ICV. (Gross air leaks from
> cracked hoses would have to be addressed beforehand as well.) Other than
> that, there is not a whole lot to be done to adjust AFR at other operating
> conditions although some CIS tuners have messed with trick control
> pressures and other weird stuff (Hello Scott J.!) to get richer AFR at WOT.
>
> DeWitt Harrison
> 1988 5ktq
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