o2 sensor question

[outback 1970]

I have a 3/4 ton with a 350 vortec 1996 my question is if I decide to eliminate the cats but retain the sensors will it set a check engine light

[Boog]

In a word yes. Without the cats there will be no cat activity which is monitored by the sensors behind the cats and a code will be set.

[outback 1970]

is there a way to trick the o2 sensors into thinking there is activity

[ChevLoRay]

One set of sensors work to modify the fuel/air ratio....while the others monitor the adjustments to see if it worked. If one said to change and the change didn't appear....how do you fool the seeker sensor into thinking that it is okay?

Several years ago, Hot Rod magazine built a 2nd gen Camaro with a hot small block. Their goal was to build a hot street machine that would pass the Cal inspection when the sniffer was shoved up the tailpipe. At that time, we didn't have computers...and their move was to overdrive the air pump and force profuse amounts of fresh air into the exhaust system. It worked.

If that is the goal of the O2 sensors as they instruct the air/fuel ratio to change, maybe a pair of AIR exhaust manifolds can be used and an air pump, Y3.

Why do you want to go to all that trouble when high performance cats are available?

All this computer stuff is aggravating, but it seems to serve some end.

[zst85]

well not my choice but when i got my 97 it had true duals and no cats cheap way i found of getting rid off the cod and ses light was some mechanical o2 sensor sims that screw into the bungs where the back ones go and then u screw the o2 sensor into that. i have had mine for about 4k miles and they work good.

[1badgmc]

Supposedly O2 sims are really hard to find now.

You can have the truck's computer re-programmed to program out those rear O2s.

[iluvmy72]

Originally Posted by 1badgmc

Supposedly O2 sims are really hard to find now.

You can have the truck's computer re-programmed to program out those rear O2s.

Yeah I tried finding some....feds sued the shiitt out of the makers and if you are caught using them, you are looking at a hefty fine. Even ebay has banned them for sale on their site due to their illegal policy. But say he does reprogram the rear ones out, the person checking for cats on inspection will notice. My advice for him is to stop trying to get around laws and deal with the cost. ODBII cats are around 300 each installed and 100 bucks for a quality sensor. The cats are not going to rob that much power but will rob a person in the wallet. I just paid $1000.00 for 4 new sensors and two cats on my 96. I'm assuming he's most likely trying to avoid that.

[Hoods69BadBowTie]

Originally Posted by zst85

well not my choice but when i got my 97 it had true duals and no cats cheap way i found of getting rid off the cod and ses light was some mechanical o2 sensor sims that screw into the bungs where the back ones go and then u screw the o2 sensor into that. i have had mine for about 4k miles and they work good.

Damn I was going to suggest the same thing. I didn't know that they were hard to find now or so illegal. I have never had anything new enough to worry about that sorta problem. What do you need them for though inspections or just to make the truck run right? My '88 has true duals no cats but its old haha.

[1badgmc]

Originally Posted by Hoods69BadBowTie

What do you need them for though inspections or just to make the truck run right?

O2 sims won't pass any inspections. Those O2 sensors behind the cats are there to make sure the cats are working. If the cats are gone, those sensors will tell the truck's computer that the cats are malfunctioning and cause issues. The sims trick the computer by telling it that the cats are there and working.

[Pondscum]

space out the sensor from the pipe using a spark plug non-fouler, its really cheap and it works

[iceship]

Any one have any pic for this cheap trick....

[bpeters5814]

Mine came with true duals and no cats. It sets off the sensor after I've been driving for awhile, but as soon as I decelerate, it goes off. Makes the truck run a little rough at start-up, but other than that, it doesn't cause any problems. My only concern is that the light might go off sometime, and I'll dismiss it thinking it's just the O2 sensors, but it's something serious. I dunno. I'm thinking about putting cats on and doing it the right way.

[bighaas79]

Originally Posted by bpeters5814

Mine came with true duals and no cats. It sets off the sensor after I've been driving for awhile, but as soon as I decelerate, it goes off. Makes the truck run a little rough at start-up, but other than that, it doesn't cause any problems. My only concern is that the light might go off sometime, and I'll dismiss it thinking it's just the O2 sensors, but it's something serious. I dunno. I'm thinking about putting cats on and doing it the right way.

You have other problems on startup then, because the downstream O2 sensors have absolutely nothing to do with how the truck starts or runs. The downstreams are there for monitoring of cat. activity and effeciency, nothing more.

[bpeters5814]

Originally Posted by bighaas79

You have other problems on startup then, because the downstream O2 sensors have absolutely nothing to do with how the truck starts or runs. The downstreams are there for monitoring of cat. activity and effeciency, nothing more.

I always assumed it had something to do with the O2 sensors, because that's the only code it throws. Wonder what the deal is?

[Boog]

You said
"It sets off the sensor after I've been driving for awhile, but as soon as I decelerate, it goes off. Makes the truck run a little rough at start-up, but other than that, it doesn't cause any problems."

Confusing. SES comes on after you've been driving a while but goes out when you decelerate and makes the truck run rough at start up?

Have you pulled the stored codes from it?
You may have a couple of different problems here.
Rough running on startup can be the coolant temp sensor. Cheap fix. The other can be egr related but really need to read the stored codes in it.
Are the front two 02 sensors in place?

[Boog]

Originally Posted by iceship

Any one have any pic for this cheap trick....

No pics but it's easy to do. There are two length adapters. Get the long one and drill the center out just enough to clear the sensor when screwed into it. Install in the pipe. 20 minute job.
This is ONLY for the rear most 02 sensors. Those sensors sole purpose is to monitor how well the cat is working. A failing cat will set off a code indicating the catylist operation is below optimum threshold. By moving the sensor out of the exhaust flow a small bit it tells the computer the cats working fine. No SES. Does not affect how the engine runs.

[bpeters5814]

Originally Posted by Boog

You said
"It sets off the sensor after I've been driving for awhile, but as soon as I decelerate, it goes off. Makes the truck run a little rough at start-up, but other than that, it doesn't cause any problems."

Confusing. SES comes on after you've been driving a while but goes out when you decelerate and makes the truck run rough at start up?

Have you pulled the stored codes from it?
You may have a couple of different problems here.
Rough running on startup can be the coolant temp sensor. Cheap fix. The other can be egr related but really need to read the stored codes in it.
Are the front two 02 sensors in place?

I haven't checked the codes lately, but last time I did, it was an O2 code. The PO had welded a bung on one of the pipes where it would've been had there been a cat. Replaced that O2 sensor and fixed it for about a day, then went back to doing the same old thing. I've still been getting 13-14 mpg with 4.10s, so I have just left it alone. If I'm driving 55-60 for an extended period of time, SES light will come on, but as soon as I slow down, such as turning the corner to take the gravel road home from the highway, the light goes off. It doesn't always run rough at start-up. It's starts fine, but sometimes when I put it in reverse to back out of the garage, it tries to die. I haven't checked the front O2 sensors. Maybe tomorrow I'll get the trusty old paper clip out and read the codes again.