Bypass o2 sensors

Ztoxic_Helix said:

I got a 1998 GMC Sierra 1500 5.7 vortex, 4l60e true duals exhaust, but I can’t figure out how to do the o2 sensors, I would much rather bypass them if possible, cause it says there supposed to have 4 o2 sensors, but I can only find the ones for the 2 at the top, my motor just revs up and down at 30, but past 30 runs great till I drop back down to 30 again, and it spits and spudders when I go from dead stop to up hill, but I know there nothing wrong with Tranny, got it up to 120 last night no problem, got mad at and wanted to blow it, done bought 3 transmissions for it

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I re-read this at least three times before I realized that it's only one, long sentence... something about O2 sensors at 120 uphill, tranny's OK though.

What's the one, motivating issue that you want to resolve. Please elaborate. One issue per posting, please.

1998_K1500_Sub said:

OMG, there certainly are.

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Think it's cuz the Vortec had 4 o2s but when you have a vortex

1998_K1500_Sub said:

I re-read this at least three times before I realized that it's only one, long sentence... something about O2 sensors at 120 uphill, tranny's OK though.

What's the one, motivating issue that you want to resolve. Please elaborate. One issue per posting, please.

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Youth, ignorance, arrogance.

Oh and American schools.

Joe Dirte said:

Think it's cuz the Vortec had 4 o2s but when you have a vortex

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Good catch. The vortex engines employed an alpha-N FI system instead of the Vortec's mass air flow FI system. Alpha-N doesn't require O2 sensors.

Ztoxic_Helix said:

When it’s on private property and you own the road I’ll drive 130 and if your family on them they already in trouble

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Strange. I reread your first post and it said nothing about being on a private road. Would've been nice to know...

1998_K1500_Sub said:

Good catch. The vortex engines employed an alpha-N FI system instead of the Vortec's mass air flow FI system. Alpha-N doesn't require O2 sensors.

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Forgive my ignorance. The heck is a "vortex" engine.
I thought OP simply misspelled Vortec, because x and c are next to each other on a "qwerty" keyboard

Should be 4 O2 sensors. Two forward of cat for mixture control. Two aft of cat for cat health monitoring. Unless you have disabled it, the computer will start pulling off fuel at 120 miles per hour. You were aware of that right. And your tires are rated for over 100 mph?

0xDEADBEEF said:

They aren't your issue.

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What do you think it is, my motor just revs up and down at 30, and it just acts like the map sensor bad going up hill, but it doesn’t have no codes except what was already there

1998_K1500_Sub said:

I re-read this at least three times before I realized that it's only one, long sentence... something about O2 sensors at 120 uphill, tranny's OK though.

What's the one, motivating issue that you want to resolve. Please elaborate. One issue per posting, please.

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I just can’t figure out why it won’t drive normal or go up hill good, if I go from dead stop to up hill it acts like a map sensor is bad, but at 30 mph the motor just revs up and down for a few seconds, but only after you drop from a higher speed

You mention having "true dual exhaust" but don't describe more than that. The 98 5.7L had four O2 sensors. The upstream ones are the ones on the Y pipe just after the manifolds and are used for the efi. They cannot be removed without also changing your entire fueling system. The downstream ones are after the catalytic converters and monitor the health of the cats. When you "upgraded" to a dual exhaust I presume you did a cat delete at the same time. Cat deletes, being awesome, obviates the the purpose of the downstream sensors so they were likely removed. You should have had someone account for this in the tune if it was done right. Or someone just pulled the CES lamp which is even more awesome than a cat delete. Or you simply ignore it being illuminated which is even more awesome than pulling it. In any event, if I had to guess, you "upgraded" your exhaust system to one that is poorly designed for your rig and are losing low end torque because of it. Maybe getting unequal backpressure between the two halves of the motor too. I'm presuming your truck ran well before the "upgrade" to dual exhaust. If not pre-existing problem made worse.

First of all, you probably have other issues, besides the 02 sensors. If the 2 rear 02 sensors are not there, then they have been removed. There is only 3 ways to fix this.
1 install bungs and new rear 02 sensors,
2 have the rear 02 sensors tuned out of the ECM, or,
3 use cat simulators.
If, you don't do any of these 3 things, the ECM will not respond correctly. Some people say, oh, it's just the rear 02 sensors, they really don't do anything, but that's where they are wrong. When I deleted my cat's, I had issues with the ECM. The truck stayed in limp mode. MPG went it $hit, performance suffered, ECT, ECT. Being I still had my OE bungs in place, I made a set of cat simulators. They have been on my trucks for several years. Never a CEL. I also have shorty headers, and true dual exhaust out the back. On mine, I did all the work myself. I simply cut the exhaust pipe rite where it went into the huge OE muffler. It is dual pipes up to there. I romoved the OE muffler, and installed 2 old school 24 inch glass packs. Then I built the 2ed exhaust pipe to go around the spair tire. Built a set of SST tips, and installed those after the tail pipe mods were done. It's probably been 5 or 6 years since I did mine, may more, IDK. The point is this, 9f youale changes to anything with a sensor, you have to make changes to the ECM, or fool the ECM.