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Fooling rear O2

oldschoolpontiacs

oldschoolpontiacs

New member
So my sis popped the motor in her '97 GTP, and we're in the middle of swapping in a good motor. I decided to just yank the whole exhaust out from under the car so I can inspect it for leaks, got to love FWD for having the exhaust run under everything so it's easy to pull. Anyway, I notice it's got a goofy U-bend deal for the rear O2 sensor, and behind that a glasspack looking thing that I assume acts as a resonator. I figure there's probably 4 or 5 hp sitting in there, so I want to chop it out and weld a straight piece of pipe in there instead. Obviously that kind of removes the space required to fit the O2 sensor back under the floorpan, and running that wire back there is a PITA anyways, so is there a way I can eliminate the rear O2? I've heard of guys putting resistors and such in to fool the computer into thinking it's reading what it wants to see, and since it still has the primary O2 upstream I can't see it causing any problems. Help?
 


resonator isnt a restriction. leave it alone so the car stays quiet.

the ubend should be taken out, though.

you can buy an o2 simulator. those just plug into the plug where the o2 sensor would go. a resistor wont work.
 
Thanks, I just checked their website, $60 Canadian before shipping. Yikes. I'll pass on that, it's a lot cheaper to just drill a hole and weld a bung into a $5 piece of pipe and reinstall the sensor
 
^^ Yeah...that works too ;) Just be sure to get rid of that U-Bend though...horrible piece of GM engineering...plus it'll give ya a little bit better gas mileage too IMO.
 


Cool thanks, now that I think of it I probably have some leftover exhaust pipe that I could use for that lying around, so if I just cut out the existing bung and reuse it this mod will cost me a whopping few cents in welding wire haha. Between that and having a motor with half the mileage of the one that kicked the bucket, I really hope my sis notices an improvement in power and economy
 
Just getting rid of the u-bend doesn't do a whole lot. The front manifold and the down pipe are still horrible restrictions.
 


oldschoolpontiacs said:
I've heard of guys putting resistors and such in to fool the computer into thinking it's reading what it wants to see, and since it still has the primary O2 upstream I can't see it causing any problems. Help?
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i can tell you from personal experience, that this trick does not work to well i have changed the resistor about 4 times already they just keep blowing, so now i just drive with the SES light on until i get you o2 eliminator
 


Dammit! The O2 sensor had been cross threaded (was a huge PITA to remove) but I decided to try and fix up the threads and reuse it to save some $$$. I got the pipe all built up, O2 bung reused from the old pipe welded in the right place, threaded the new O2 in for a test fit under the car and after it wouldn't come back out. Threaded in nicely...but wouldn't come out...long story short, neither the sensor nor the bung have threads anymore. A new sensor is about $90, so she's going with the ZZP emulator. F$%K!!!!
 
oldschoolpontiacs said:
Dammit! The O2 sensor had been cross threaded (was a huge PITA to remove) but I decided to try and fix up the threads and reuse it to save some $$$. I got the pipe all built up, O2 bung reused from the old pipe welded in the right place, threaded the new O2 in for a test fit under the car and after it wouldn't come back out. Threaded in nicely...but wouldn't come out...long story short, neither the sensor nor the bung have threads anymore. A new sensor is about $90, so she's going with the ZZP emulator. F$%K!!!!
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Just wondering where in the hell you buy sensors FROM?!?! ZZP sells them for about 40-50 bucks.
 
Canada...we get raped on everything. ZZP sells the emulator for $50 too, but that's $60+ in our money, and then another $30-40 by the time it hits our door. Same for the O2. Folks in the US don't realize how dry we take it up here, even when our dollars were the same we were still paying more for everything just because companies get away with doing so. It's really irritating.
 
oldschoolpontiacs said:
Canada...we get raped on everything. ZZP sells the emulator for $50 too, but that's $60+ in our money, and then another $30-40 by the time it hits our door. Same for the O2. Folks in the US don't realize how dry we take it up here, even when our dollars were the same we were still paying more for everything just because companies get away with doing so. It's really irritating.
Click to expand...

yea that really sucks for you canadians. hard to get parts
 
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