Test pipe and O2 spacer with catalyst

[xstwin]

Oh you're gonna hate me for this one......Try another post-catalyst sensor. Sound's like the one you have in your car is very high tolerance (too sensitive). When they manufacture those things, not all are created equal. Otherwise, if you're really adamant on making this work with your current setup, the best solution is to put a dual channel oscilloscope on both sensors and compare the reading. While they shouldn't be the same, the delta between the two signals should be sufficient to "fool" the ecu that all is Ok. Sorry to geek out on you, but the days of the carburetor are long gone.

[jordancl]

Oh you're gonna hate me for this one......Try another post-catalyst sensor. Sound's like the one you have in your car is very high tolerance (too sensitive). When they manufacture those things, not all are created equal. Otherwise, if you're really adamant on making this work with your current setup, the best solution is to put a dual channel oscilloscope on both sensors and compare the reading. While they shouldn't be the same, the delta between the two signals should be sufficient to "fool" the ecu that all is Ok. Sorry to geek out on you, but the days of the carburetor are long gone.

O2 sensors are not cheap and I don't want to buy another one and have a similar issue. I might consider swapping the front and the rear, but I'm not sure. The other option that seems more presentable to me at the moment is to try to space the sensor out a smaller distance to avoid the 0422 and the 2096. The 90* sensor comes in two pieces, the mini cat, and then spacer. I wanted to try to screw the o2 sensor directly into the mini-cat, but it seems the threads are not the same. If only there was software to ignore P0422 AND keep the second o2 sensor ready/active :(

Most important thing to add to this thread is that I have absolutely no evidence that the Strat spacer "doesn't work". In fact, if anything it seems to work too well, but so did the 034 basic spacer.

[xstwin]

jordancl, I've got an extra 1/4" spacer (more like washer) that will thread onto the 02 sensor. Should leave about 2.5 threads left. I'm in NJ, will gladly drop it in the mail. Send pm if interested.

[jordancl]

Thanks for your feedback @jordancl. As I understand this the front O2 sensor and MAF contribute to air trim calculations while the rear O2 sensor is simply monitoring the cat? i'm new at this but based on the trim readings varying with the presence of the spacer, it almost sounds like you're putting the spacer on the front sensor. ?? does the rear O2 sensor contribute to trim calculations? if so, how would a spacer or disabling it via APR stage2 actually work right?

I'm quite curious to fully figure this out as I just received my HFC and 90* spacer and am wanting to run this w/ the rear O2 sensor active+no cel and no faults.

This is the way I understand it. The front O2 sensor reads exhaust gasses going into the cat for hydrocarbon levels. The rear sensor reads exhaust gasses coming out of the cat and reads for hydrocarbons also. If the cat is functioning, there is a decrease in hydrocarbons in the exhaust gas at the rear o2 sensor because the catalyst has converted them into CO2 and H2O.

With no spacer and a high flow cat, the rear o2 sensor is seeing more hydrocarbons than it would w/ the stock cat because the gas is passing through the cat more quickly and it is not converted as well. Of course the car doesn't know or care that you put in a higher flow cat; all it knows is that its seeing too many hydrocarbons after the cat and it throws a P0422 ** cat below efficiency threshold. The car essentially thinks your catalytical converter is broken.

Putting a spacer in steps the o2 sensor back out of the cat so its not right in the middle of everything. The idea behind a spacer is to not let the rear o2 sensor see some of the hydrocarbons in the exhaust gas so it thinks everything is OK and it doesn't flip out as above. However, as I stated originally, the rear sensor does expect to see SOME hydrocarbons because even the stock cat isn't perfect. So if you space it out too far, and it doesn't see ANY hydrocarbons it figures there must not be enough gas getting to the engine (running lean).

As far as I can tell, I'm the only one who has had a problem like this on the forums thus far, so if you have a spacer in your hands I'd just throw it on and try!

jordancl, I've got an extra 1/4" spacer (more like washer) that will thread onto the 02 sensor. Should leave about 2.5 threads left. I'm in NJ, will gladly drop it in the mail. Send pm if interested.

I will definitely try this and paypal you shipping $$ ** PM sent

[a4_bob]

With no spacer and a high flow cat, the rear o2 sensor is seeing more hydrocarbons than it would w/ the stock cat because the gas is passing through the cat more quickly and it is not converted as well. Of course the car doesn't know or care that you put in a higher flow cat; all it knows is that its seeing too many hydrocarbons after the cat and it throws a P0422 ** cat below efficiency threshold. The car essentially thinks your catalytical converter is broken.

right, the rear sensor detects in the same way as the front but with different intent; broken cat vs fuel trim. I don't understand why the rear sensor would take part in fuel trim functions. It still sounds like something's off up front, as StratJohn was suggesting some posts earlier. The spacer on the rear almost sounds coincidental. Just my noob reasoning...

Good luck getting it straightened out. I'll post my results next week after installation.

[jordancl]

right, the rear sensor detects in the same way as the front but with different intent; broken cat vs fuel trim. I don't understand why the rear sensor would take part in fuel trim functions. It still sounds like something's off up front, as StratJohn was suggesting some posts earlier. The spacer on the rear almost sounds coincidental. Just my noob reasoning...

Good luck getting it straightened out. I'll post my results next week after installation.

I checked my codes for the cat two days ago and noticed I had the lean code 7/25, and then the too rich code a few days later. I cleared the codes hoping that the ECU would find the right mix to keep the sensors happy w/ the spacer, but I got a CEL about 30 miles later. Checked that code today and it's too rich. I'm pretty sure this rules out an exhaust leak from loose bolts or faulty gaskets, but I'm not sure. To be continued I suppose...

[a4_bob]

Readiness test now shows 1 fault which showed up two days after the install - Lean from the post catalyst O2 sensor. No CELs (yet).
damn...