no cats how lean

[19doug90]

if i delete my cats but still have the downstream 02's how lean is the computer going to put the motor because of this

would be nice if someone whos done this before could chime in.

its on a 97 yukon

[dave89iroc]

downstreams have no effect on the fuel/air mix, that is the upstreams, the downstreams are for cat monitoring only, you will get a check engine light until you get a tune though

[19doug90]

ah right on, i knew the downstreams monitored the cats but figured if it was reading the cat being seriously rich it would lean out the engine a bit. Guess not tho.

So could i just delete the downstream 02's completly and live with the check engine light? when i was going accross the country i lost an 02 and the truck went into a borderline limp home mode, gobs of fuel lost 1/3 of my gas mileage until i got it fixed. But the reader said both the upstream and 1 of the downstreams were bad.

Was this just caused by my upstream going out or if i completly disconnect the downstreams might this happen?

[PHATSPEED7x]

I deleted the cats on my 98 and never got a SES light for some reason. And I never got a custom tune.

[19doug90]

Originally Posted by PHATSPEED7x

I deleted the cats on my 98 and never got a SES light for some reason. And I never got a custom tune.

did you still keep the downstreams in place tho?

EDIT: obviously you did or youd get an ses light, k im not real worried about it then