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+--- Thread: To tap or not to tap? (/showthread.php?tid=6974)
To tap or not to tap? - WRXtranceformed - 02-08-2008
Dunno if I've posted about this here or not, but I've had a problem with a P0141 CEL for a while now, meaning the Bank 1 O2 sensor 1 is dead. I bought a new one to replace it and my friend and mechanic in VA was trying to replace it for me when he heard the thread in the bung start to strip. He stopped, screwed it back in and left it as it was because I was moving literally the next day and wasn't sure what I wanted to do. Apparently the sensors come from the factory screwed in VERY tight to the manifold and this is a pretty common occurrence.
So now I'm faced with some options. I'm trying to keep my costs as low as possible since I'm closing pretty soon on the house.
1) Free CEL fix. Basically I wire the sensor leads on the ECU harness from B1S1 to B2S1 to trick the ECU into thinking the O2 sensor is working. Works fine until the second bank's sensor (cylinders 4-6) decides to die. Desireable because it's free, not desireable because if an injector sticks open or there is some knocking in the first 3 cylinders, it will go undetected. Being as reliability is key for me, I'm not leaning toward this option despite its fantastic price.
2) Pull the manifold and the sensors, retap the bung or replace the bung if the job gets botched. My buddy I think has the tools to retap it and said he'd be willing to help me do it. This is desireable also because it's free, but there is some uncertainty as to whether or not it will work and I can't afford for my car to be down for a couple of days. What we don't have is welding tools so replacing the bung, if it came to that, would just add cost and more downtime.
3) Purchase an OEM manifold and just do the simple swap. I've found used OEM manifolds for about $100 not including shipping (~$40-$50). Many of these of course have stripped bungs, some do not so it's kind of hit or miss. I'd of course find out before I bought it.
4) Purchase an aftermarket manifold and just do the simple swap. I negotiated a killer deal ($210 shipped) on ceramic coated Toyomoto headers and Y-pipe and I think the gasket I need too. Downside: most expensive option. Upside: More power! :twisted: , only about a $60 difference once shipping is factored in (probably less once gasket is factored in) for more exhaust pieces, I can probably flip the OEM manifold to recuperate the costs.
Thoughts??? I'm *this* close to pulling the trigger on the aftermarket headers, but I thought maybe you guys had some input.
- Maengelito - 02-08-2008
if the sensor is before the cat, i'd replace it. its a good excuse to upgrade to that header if you're interested. on my old miata, i had to relocate an O2 sensor after the main cat because of it was the stupid california emissions model. i bought a nut of proper thread size for like 79 cents or something, took it to a muffler shop and paid a guy $20 to weld it on. took a total of 30 min.
not sure if your exhaust mani is cast iron or not, but maybe the threads on the old sensor are stripped and not the bung its in? maybe taking it out and running a thread chaser through it might clean it up a bit.
- WRXtranceformed - 02-08-2008
Ah yeah, if you guys have any other suggestions I haven't thought of yet, by all means let me know! So Maeng you basically just used a nut that fit the size of the sensor as a new bung? Did the guy weld it on while the exhaust was still on the car?
Here's a picture of the stock manifold and the B1S1 location:
![[Image: DSC00696.jpg]](http://i6.photobucket.com/albums/y217/aageraci/DSC00696.jpg)
So yeah it's precat.
Edit: And as a comparison, the Toyomoto headers
![[Image: DSC008661.JPG]](http://www.clublexus.com/gallery/data//500/medium/DSC008661.JPG)
- Evan - 02-08-2008
fwiw, i ran without a o2 sensor for a while. it doesnt hurt your engine. in fact i got better gas mileage that way.
its strange that a cast iron manifold got stripped by a steel sensor, but i guess if it happens a lot on that car then it is certainly possible!
if the wiring fix truely works and has been done then that is actually pretty surprising. A o2 sensor sends oscillating voltage, not something constant, which is why simply using a resistor wont work. I plan on building a o2 simulator with a breadboard and a 555 timer to fix my cel.
edit: i think i misread your wiring solution. n/m. and holy fuck your car has too many damn o2 sensors.
personally id just do the aftermarket headers anyway. easy solution and you're a ricer anyway.
- WRXtranceformed - 02-08-2008
Agreed on all counts. I forgot to mention that the seller of those headers is including the o2 simulator in that price as well, and is definitely including the gasket. I'm not terribly concerned about this CEL but I have been getting worse gas mileage because I think the ECU is causing the car to run richer as a safety measure. I'd also really like to not be stranded out in Boone on the off chance that I do have something go wrong in those cylinders... with my luck, it would :lol:
- ViPER1313 - 02-08-2008
Evan Wrote:I plan on building a o2 simulator with a breadboard and a 555 timer to fix my cel.Save yourself the time and just spend $20 to have one shipped to your doorstep. I bought one from some Ebay electronics shop for the GL over a year ago - still works great, no CEL, passed OBD2 emissions test without issue.
- Evan - 02-08-2008
ViPER1313 Wrote:no shit, all the ones i saw were around $50 but i didnt look on ebay. do you remember the seller?Evan Wrote:I plan on building a o2 simulator with a breadboard and a 555 timer to fix my cel.Save yourself the time and just spend $20 to have one shipped to your doorstep. I bought one from some Ebay electronics shop for the GL over a year ago - still works great, no CEL, passed OBD2 emissions test without issue.
- Maengelito - 02-08-2008
WRXtranceformed Wrote:Ah yeah, if you guys have any other suggestions I haven't thought of yet, by all means let me know! So Maeng you basically just used a nut that fit the size of the sensor as a new bung? Did the guy weld it on while the exhaust was still on the car?
yeah, i might even have an extra nut lying around because i bought a couple incase something went wrong. i'll have to sort through my box of loose nuts and bolts. the guy welded it on the exhaust with the car on a lift and exhaust still attached. i'm sure you could go to any muffler shop and they'd do it for you. in fact, i bet they have bungs there that they could weld on as well.
- Ginger - 02-08-2008
Yeah, even proper o2 bungs only sell for a couple dollars online.
- D_Eclipse9916 - 02-08-2008
Evan Wrote:fwiw, i ran without a o2 sensor for a while. it doesnt hurt your engine. in fact i got better gas mileage that way.
its strange that a cast iron manifold got stripped by a steel sensor, but i guess if it happens a lot on that car then it is certainly possible!
if the wiring fix truely works and has been done then that is actually pretty surprising. A o2 sensor sends oscillating voltage, not something constant, which is why simply using a resistor wont work. I plan on building a o2 simulator with a breadboard and a 555 timer to fix my cel.
edit: i think i misread your wiring solution. n/m. and holy fuck your car has too many damn o2 sensors.
personally id just do the aftermarket headers anyway. easy solution and you're a ricer anyway.
You may have gotten better gas mileage compared to the o2 sesnor being dead and being put into constant open loop mode. You may get close to the same mileage without an o2 sensor, but do you really think that running without a proper o2 is going to allow the engine to compensate fuel trims in closed loop mode properly? You probably wont notice that much of a difference, but the difference is there, the ECU is no longer monitoring so lo and mid fuel trims are going to be a guesstimate on your o2 simulator.
Edit: My vote...do it proper and go ahead get the aftermarket one for more power, as long as its made properly you shouldnt have a problem with a tubular manifold that isnt holding any weight.
- WRXtranceformed - 02-08-2008
I've heard from my mechanic that it's 50/50 whether you get improved or worse fuel mileage when an O2 sensor goes bad. I happened to get the worse I guess!
- HAULN-SS - 02-08-2008
how hard could it be to retap it? Thats like a 2 minute job. Is it hard to get to while on the car or something?
- WRXtranceformed - 02-08-2008
It's a Jap motor... nothing is exactly in the easiest spot to get to.
- ViPER1313 - 02-08-2008
D_Eclipse9916 Wrote:Evan Wrote:fwiw, i ran without a o2 sensor for a while. it doesnt hurt your engine. in fact i got better gas mileage that way.
its strange that a cast iron manifold got stripped by a steel sensor, but i guess if it happens a lot on that car then it is certainly possible!
if the wiring fix truely works and has been done then that is actually pretty surprising. A o2 sensor sends oscillating voltage, not something constant, which is why simply using a resistor wont work. I plan on building a o2 simulator with a breadboard and a 555 timer to fix my cel.
edit: i think i misread your wiring solution. n/m. and holy fuck your car has too many damn o2 sensors.
personally id just do the aftermarket headers anyway. easy solution and you're a ricer anyway.
You may have gotten better gas mileage compared to the o2 sesnor being dead and being put into constant open loop mode. You may get close to the same mileage without an o2 sensor, but do you really think that running without a proper o2 is going to allow the engine to compensate fuel trims in closed loop mode properly? You probably wont notice that much of a difference, but the difference is there, the ECU is no longer monitoring so lo and mid fuel trims are going to be a guesstimate on your o2 simulator.
Edit: My vote...do it proper and go ahead get the aftermarket one for more power, as long as its made properly you shouldnt have a problem with a tubular manifold that isnt holding any weight.
You are correct - you can't use an eliminator for the front O2 sensors. The rear O2 sensors have nothing to do with fuel management however - they are only there to measure the emissions after the exhaust has been filtered by the cat. Thus, a car with a bad catalytic converter (like my GL) will throw a CEL if it detects that the converters are not doing their job. Adding an eliminator for the rear O2 will do nothing except fool the computer into thinking that the car is running extra special clean, keeping the CEL off and making the car pass emissions.
Guess I should have specified that I used the eliminator for the REAR O2s :wink:
- WRXtranceformed - 02-08-2008
Good posts guys. Yeah I was planning on using the eliminator for the rear ones if I was going to replace it with an aftermarket unit since they're for emissions only basically. The one that is dead is a precat sensor like I said before, so all I need to do is replace it so it can read the a/fs. And since I'm not playing with the fuel trims / ECU otherwise, it should read a-OK!
Edit: I'm leaning more and more toward just snagging those aftermarket heads. I may stop by an exhaust shop to see how hard it is / how much it will cost to weld in a new bung. I could just leave the old sensor in its bung and pop the new one in right next to it. I'm just getting a bad feeling about trying to retap it ourselves, and when I get a bad feeling it's usually for a good reason with car related stuff. :lol:
- Evan - 02-08-2008
D_Eclipse9916 Wrote:but do you really think that running without a proper o2 is going to allow the engine to compensate fuel trims in closed loop mode properly? You probably wont notice that much of a difference, but the difference is there, the ECU is no longer monitoring so lo and mid fuel trims are going to be a guesstimate on your o2 simulator.I agree to a certain extent, but I also think that you are over exaggerating the role that an o2 sensor plays, at least in an engine /ECU like mine that was originally designed for pre ODB days. Exact optimal fuel mix? Probably not (but o2 sensors arent that accurate anyway) optimal power and fuel economy? probably not. Enough to any damage or any adverse affects, no way.
In the more complicated world of forced induction ECUs the o2 sensor plays a larger role, I have no doubt.
- ViPER1313 - 02-08-2008
Evan Wrote:Trying to use an eliminator on the front O2 is risky at best and a horrible idea in any case. When no O2 sensor is hooked up, the ECU will run default trims across the board that have been programmed by the factory, keeping the engine at least partially safe. With an eliminator hooked up to a front O2, the on/off will be a constant rate that the ECU will accept as valid but is not in any way related to how rich or lean the engine is running. I would not be surprised if it made the motor run catastrophically lean at mid RPM / mid throttle operation.D_Eclipse9916 Wrote:but do you really think that running without a proper o2 is going to allow the engine to compensate fuel trims in closed loop mode properly? You probably wont notice that much of a difference, but the difference is there, the ECU is no longer monitoring so lo and mid fuel trims are going to be a guesstimate on your o2 simulator.I agree to a certain extent, but I also think that you are over exaggerating the role that an o2 sensor plays, at least in an engine /ECU like mine that was originally designed for pre ODB days. Exact optimal fuel mix? Probably not (but o2 sensors arent that accurate anyway) optimal power and fuel economy? probably not. Enough to any damage or any adverse affects, no way.
In the more complicated world of forced induction ECUs the o2 sensor plays a larger role, I have no doubt.
- Evan - 02-08-2008
I agree, I wouldnt use an eliminator in the front. Better to have no data than false data. I did have no front o2 for a while.
- Ginger - 02-08-2008
Evan Wrote:I did have no front o2 for a while.
Ditto. Worse things have happened.
- ViPER1313 - 02-08-2008
One more point - most O2 sensors have a 60-100k mile lifespan, and if the first sensor has failed you should consider replacing all 4 at once. Don't cheap out either - go with Bosch or Toyota OEM.
On the other hand if you are feeling super cheap, you probably have the option swapping the lower 2 O2 sensors into the upper 2 positions and running an eliminator for the lowers (I know the 4 sensors on a Taurus are the exact same sensor, YMMV.)