'86 CGT failing emissions..ideas? tips to get it to pass?wheres the EGR ...

Alan Kramer ackramer at hotmail.com
Tue Jul 31 09:48:28 EDT 2001

Looks like you need to richen up your mixture a bit, that'll reduce NOx but 
increase HC / CO (which you have room on).  You can't fool around with your 
static mixture setting because as soon as you are off the idle switch, your 
in computer control, so your static mixture setting doesn't do jack to help 
(as long as it's in the ballpark.  Is it?) .  Assuming your oxygen sensor is 
brand new (You've replaced it already, right?)  and you still have the 
problem, you have two ways to fool the computer into sending more gas to the 

1)  Experiment with putting a resistor in parallel with your oxygen sensor, 
one end going to ground, the other to the oxygen sensor lead.  This will 
trick the car into thinking it's leaner than it really is.   You'll need to 
do some experimenting as to what value to use...

2)  Trick the car into thinking it's colder than it really is.  This will 
increase the current to the CPR on the fuel dizzy.  I do this on my '83 CGT 
("upgraded" w/ CIS-E) to increase my fuel flow at WOT.  I have relayed in a 
2000 ohm resistor into the coolant temperature sender located on the bottom 
of the upper radiator hose flange at the head.  At WOT, the SPDT relay flips 
the 2000 ohm resistor in series into the coolant circut.  The car now thinks 
it's cold(er) and increases the milli-amperage to the FPR.  You can do this 
across the whole throttle range by permanently splicing in a resistor to 
that circut.   Of course use a much smaller one, I'd suggest starting at 
800-1000 ohms and going from there.  You can check the change by monitoring 
the current to the FPR and the voltage at the oxygen sensor.  Of course the 
best way to do it is with an EGA.

Good luck,

'83 CGT
'85 CGT turbo project
'86 4kcsq

> >
> > The only thing it is failing as I mentioned is Nox.  The Nox is high.  I
> > suspect the EGR at this time. All other items check out.
> >
> > The standard in GA is 1100 ppm, the car is putting out a little over 
> > ppm.  CO and HC are WAY below the max.
> >
> > Lambda is set at 45%, O2 Sensor is working normally, Cold and Hot Fuel
> > Pressures are in spec, Cat is ok, Timing reset to 6 degrees BTDC as per
> > specs.  The timing change alone brought the Nox down from 2700 to 2100.
> >
> >
> > Atlanta Emmissions run a car at 25 MPH above 2500 RPM for three minutes 
> > a treadmill.  It is not a standing emmissions test as in most states.
> > >
> >

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