[sbilbrey]

I bought an ebay header and flex pipe. I have always been concenred about the cat in the exhaust manifold being broken up and my flexpipe had a big hole in it. I removed the current exhaust manifold and found four CO2 sensors. 2 before the inline cats and 2 after. The new header only has two places to add CO2 sensors. There is no built in cat either.

My question is do I splice the current four down to two? This seems stright forward enough.

Or, do I plug in the two pre-cat sensors and leave the aft-cat sensors out? This could seem right, since there is no cat in the new setup.

Other question, what is the effect of these sensors not being plugged in? Engine Light, or something worse.

I have inserted (I hope) a couple photos.

Thanks
Sammer

 

[i68k]

well, the bolt pattern looks like a 1.8, not sure why there's only 2 bungs tho. i havent seen a header yet with the spacer welded on like that, usually you foul out the lower o2 of the pair. if you do it wrong, yes your engine light will come on and the car will run crappy

but my educated guess would be that youre missing the second piece of your header, or didnt picture it. that one piece is a lot shorter than your stock header. are there o2 bungs on the next piece after the manifold, i think your new flex section? the mounting location for the lower o2 sensors is below the flange on your new header, should be on next piece.

 

[sbilbrey]

Thank you for the reply.

The bolt pattern is good, I have had it on the motor.

Here are a couple more pics:

I included the one with the 2 bungs to show that there is the separate bung that is welded on, but that is for the heat exchange pipe.

Since there is no cat in the header or downpipe, does it really matter if those sensors are plugged in?

It seems that the top two sensors have exactly the same three wires & the bottom has the same four wires, so it seems easy to splice.

Thanks,
Sammer

 

[i68k]

oh right, forgot about the egr.

im not sure about splicing wires, even tho it seems easy, these wires are voltage specific. you should do more research or send a message to one of the mods, jp or blackb15, they seem to know more about the 1.8s.

the ecu will need to get some sort of reading from all 4 o2 sensors, so not plugging them in usually isnt a good option. for the 2.5s we just foul-out the lower o2 sensors so theyre not in the exhaust stream. if you used all 4 o2 sensors, without a cat being present, you'll get a p0420 cat failure code.

they placing of the bungs seems to be for both upper o2 sensor. not sure about the lowers, maybe the manufacture had o2 sim or rewiring in mind.

 

[sbilbrey]

I ended up plugging in the top two sensors and leaving the lower two dangling.

One of the reasons I went to the header is that my car routinely throws the p0420. That and my flex joint was rusted out and leaking big. I admit I bought a eBay header and flexpipe for less than the flexpipe alone was running.

I would like to clear all the codes, but mostly I want the car to run right. Does the p0420 affect the computer settings or is it just informative?

Also, I tried searching on o2 sim and could not find anything, can you post the link?

With just the header and flexpipe it is way louder than just the mani & flexpipe was, although that was not quite. I had to drill out the bolts to the cat, but I got them out and found some new ones. I will have the last of the exhaust together this weekend.

Thanks for your help,
Sammer

 

[Black B15]

The ghetto sim is just a spark plug anti fouler drilled out to 1/2". Some people need to use 2 of them together to work right.

I am not familiar with that manifold setup for the 1.8, I assume it is like an 03 or older. It might be an option to get another bung welded on the header. I can't say for sure because my 1.8 only had 2 sensors not 4.

 

[i68k]

I ended up plugging in the top two sensors and leaving the lower two dangling....

doing this alone without using antifoulers or o2sim will throw a p0420 code or an o2 sensor code.

...I would like to clear all the codes, but mostly I want the car to run right. Does the p0420 affect the computer settings or is it just informative?....

while your ses light is on with that particular code. you engine will run slightly to moderately rich. meaning youll have a lower mpg. once you clear the code, it will correct itself, or if you have drive-by-wire, you can do the idle relearn.

they put bungs in wrong places on the specv headers too, so your ebay stuff maybe the same problem. it couldve been manufactured for a certain year like 02-03 for example, but still fits your vehicle with o2 relocation. except the specv ebay headers have o2 bungs, just the wires are too short to reach the midpipe from the lower o2.

i would take it to a mechanic/welder/muffler shop to have them weld in bungs for you. you will need 2 antifoulers on each of the lower o2 sensors.

 

[sbilbrey]

The four bungs are because everything is done in two cyclinders before they come together into one. I like the idea of taking it to a muffler shop and having two more bungs added so I can add the remaining bungs. But, the bottom o2 sensors used to be located after the in-manifold cats. Now these don't exist. Should I get the bungs added after the only remaining cat? That seems reasonable, but I will need to extend the wires quite a bit.

Thanks,
Sammer

 

[i68k]

yes, you can put the bungs whereever you want, but you dont want to extend the wires more than you have to. so somewhere near their original location is suggested. you can use the antifoulers to space them out so you dont get a p0420. if you over-extend the wires, resistance increases as wire length and guage increases. it changes because the signal has to travel over a longer wire, so this will mess with the readings coming from your o2 sensors. you can safely extend the wires using solder without a lot of issues, but im not sure how far you can extend without have voltage/resistance issues.

 

[sbilbrey]

Does anyone know the thread pattern on the O2 bungs?

I am going to weld two more bungs to the header. The stupid bungs are expensive, I am thinking of just using a nut with the correct thread pattern.

Also, instead of going with the o2 elimination with the drilled out spark plug, I am thinking of spacing the bungs out by stacking two or three and welding. Any comments?

Thanks,
Sammer

 

[i68k]

you can use a nut with the same threads, ive seen many people weld nuts on. you could take one of your dangling sensors off, go get some anti-foulers for couple bucks. then goto the hardware store like home depot and find nuts that fit. just make sure you get stainless or galvanized nuts if possible so they dont rust too fast.