removing catalytic

[clayrwilliams]

I have an old 90 tracker with a couple inches of body lift and mud terrrain 235/75/15 and was thinking of cutting the cat out to improve milage a little. Will this affect my O2 senser?

[95 Tracker]

your probably going to cause problems with your cat out from info i've gathered on the forums
because this is a small 4cyl you will loose power taking it out(you need some back pressure)then the check engine light will come on killing your gas milege

i don't know what you o2 senor would do it's before the cat but theres something that will know the cats not there

[jtetidrick]

i ahve a 90 sidekick without the cat. but the cat wasnt there when i bought it.i had to have a custom y-pipe made coming off the manifold. the pipe is 2.25. i however do have a stock muffler on the truck. and out of the muffler the pipe is back to i think 1.75. but i have plenty of back pressure and get around 20-23 mpg.my o2 sensor wasnt affected as far as i know.but along with the mileage i also have 31's on it.

[jtgh]

the ECU ,was tuned for a working cat.
on some cars, 90's the EGR dont need a cat. but this one does.
O2 s not an issue.

no cat
no proper back pressure.
then the EGR MOD sticks full open. (bad ,very bad)
then the vacuum from TB goes directly to the EGR full time full bore. (ported vacuum)
this causes excessive EGR feed.
this causes, loss of power and lost of MPG.

but many are happy slugging in the mud and over rocks with motors just like above.
YMMV

20mpg, that is not good. i get that in a full size 4000 lb 8v powered Chevy.

the reason the 90 dont set codes is because they didnt have a EGR monitor back then, on many.
i believe the first EGR monitor for sidekicks happened on Calif. cars.
in 91 or 92.

the ecu on 90s is vastly diff and vastly dumber.

as 95tracker says, the ecu can go to limp home if it THINKS, it has lost control.
the reason it can do that is because.
A: it can not control AFR properly. (o2 Closed loop drop out)
B: it has no idea what is wrong( it dont have the 25 monitors of modern cars)
C: it cant send a code because of B, all it knows is, I cant do my job! (good spark, and perfect AFR)
D: the ECU has no redundancy , and trusts all sensors and actuators to do there job, if not, Limphome mode happens and power is lost and gas just wastes out the tail.


Limphome = retarded ign timing, and rich on purpose.
High CO.
HIGH HC
out tail.