Header-related CELs

[Frodo]

Several years ago my kids bought me a set of headers (ebay specials) for the car...not something I'd likely have bought myself, but I wasn't necessarily opposed to the idea. A few months later, my older son and I got out the tools and jack and jack stands and, over the course of an afternoon, got them installed.



I'm happy with them, but the downside that was created has been a persistent CEL ever since because, in the process of adding headers, we eliminated one of the two catalytic converters on each side. There are 2 bungs on each header (visible in the pic), but with no cat in between, the readings on the second, 'downstream' one are way off, hence the CELs. I slap the scanner on it from time to time and get codes that are all referable to the headers/O2 sensors. That being the case, other than to check occasionally, I've largely ignored the CEL. The car seems to run fine, no loss of power or mileage issues, etc.

I'm now at 86k miles on the odometer and am starting to conclude I'm about at the point I could use a clutch. It's not really slipping, but the other concern I have is getting an IMS bearing retrofit (or the IMS Solution—haven't decided yet) installed in conjunction with having the clutch done. Problem is, LN Engineering & Flat 6 Innovations are very picky about insuring vehicles getting their IMSB products are in good shape, probably so as to NOT potentially impugn their IMSB product if the car's engine self-destructs due to some other cause. (I don’t blame them on this.) Anyway, as a result, the installers I’ve been talking with are apparently uncomfortable proceeding with a car with unresolved CELs.

I know this was kind of a Mickey Mouse approach, but not having an obvious better option available to me, I attempted to circumvent the O2 sensor using a couple of spark plug defoulers. I actually started with relatively short, straight ones. When they didn’t resolve the problem, I upped the ante and got these angled, longer ones, one of which is shown in the photo below. They didn’t work either. Had one of the technicians at a local Porsche dealership look at them and he assured me they weren't long enough to eliminate the CEL.



Continuing to Mickey the problem, at first I thought in terms of getting a couple more defoulers and stacking them with the first. Having to mess with getting two more bothered me to no end and got me to thinking: What would happen if I drilled a small hole in each of the two defoulers already on the exhaust? I’d start small—1/16” maybe. Then clear the CEL with my scanner and drive for a while. If it returns, go with the next size: enlarge it to 5/64”, again clear the CEL, and drive again. Etc, etc, til the CEL decides not to come back. Long lead-in to a simple question: Anybody think that might work? Mickey wants to know

[jcslocum]

I think you need to put the fooler after the cat. The ECU is looking at the delta between the 2 and not see enough differential. What codes are you getting??

[itsnotanova]

I also used the foulers on my exhaust system after installing a 3.4 with headers and cat deletes. I would get a CEL every so often and have to erase the code to get the light to go away. It was always the left rear O2 sensor. I even changed out the rear sensors hoping that would help. I ended up taking my box to a friend who threw a ROW tune on it and I haven't had a light since. ROW tune doesn't care about the rear O2 sensors

[LEJ]

At 62000 miles I got a Check engine light telling me that the O2 sensors were "aging" Cleared the code and got it again. The code was for a specific O2 but I went ahead and bought 4 and replaced them all. No more Check Engine Light issues. You indicated that you have 86,000 miles, I suspect your 02's are also "aging"

[Frodo]

Originally Posted by jcslocum

I think you need to put the fooler after the cat. The ECU is looking at the delta between the 2 and not see enough differential.

So I should probably just hook up with some local muffler/exhaust shop, have them add a bung downstream from the 2nd cat and extend the line to that point? No huge amount of expertise required to do this I would assume..

Is there anybody out there who's used that approach to this problem?

Originally Posted by jcslocum

What codes are you getting??

P0102, P0133, P1133, P1126

The last 3 have to do with O2 sensing; the first is apparently MAF related, ie possibly unrelated to the headers? Don't think I've ever done any tinkering with the MAF on this car..

[Frodo]

Originally Posted by itsnotanova

...I ended up taking my box to a friend who threw a ROW tune on it and I haven't had a light since. ROW tune doesn't care about the rear O2 sensors

This sounds appealing, but I don't know anyone in the area with a PIWIS/PST2.

I guess the other issue that comes into play is the fact that Ohio does intermittent (every 2 or 3 years?) "E-Checks" (ie emission checks). So far I've gotten by. I've used the scanner to eliminate the CEL just before taking the car in and it seemed to work. Last time, however, when they hooked up the electronics and read the thing they asked if I had recently been working on the car. I answered yes (sort of true ), so they then did the 'sniffer test' (ie checked what was coming out the tail pipe) and she passed.

Anybody know--which approach to resolving the CELs will minimize hassle when it comes to the E-Checks?

[Frodo]

Originally Posted by LEJ

At 62000 miles I got a Check engine light telling me that the O2 sensors were "aging" Cleared the code and got it again. The code was for a specific O2 but I went ahead and bought 4 and replaced them all. No more Check Engine Light issues. You indicated that you have 86,000 miles, I suspect your 02's are also "aging"

With similar provocation I replaced just the 2 post-cat O2 sensors at 53k miles. That resolved my then-current CEL problems until (7k miles later) we installed the headers.

I hate to randomly replace all 4 of them when I'm pretty sure at least part of my problem is the headers. They're not exactly dirt cheap! Is there any way to actually check whether an O2 sensor is in good shape or not??

[itsnotanova]

Don't quote me on this, but I believe the last two O2 sensors only tell the car that the precats are/are not doing their job. The rear O2's don't actually tell the motor to change anything. The ROW flash will turn off those rear O2 sensors so they won't trigger an engine light.

[jcslocum]

Here is some 02 info:

\\https://sites.google.com/site/mikefocke2/oxygensensors

You have removed the main cat and it may be that the secondary cats just are not up to the job of getting the numbers right. We did just the opposite, and removed the secondary cats and the pipes had a bung for the 02 sensors. All works well and the Durametric shows all normal operation and readings.

[Frodo]

Originally Posted by itsnotanova

Don't quote me on this, but I believe the last two O2 sensors only tell the car that the precats are/are not doing their job. The rear O2's don't actually tell the motor to change anything. The ROW flash will turn off those rear O2 sensors so they won't trigger an engine light.

Yeah, from everything I've read that's right. Again, though, I don't have the means to reprogram it. And I suspect shops in the business of working on cars would't be willing to do so---I suspect (though don't know for a fact) that that would get into legality issues.

I'm in Ohio...anybody in this neck of the woods with a Durametric, etc, that would be able to help with this? Feel free to PM. (BTW, I confess that I'm unclear on my terminology: Durametric vs PIWIS vs PST2...the distinction between them I'm a bit unclear on )

[Frodo]

Originally Posted by jcslocum

Here is some 02 info:

\\https://sites.google.com/site/mikefocke2/oxygensensors

You have removed the main cat and it may be that the secondary cats just are not up to the job of getting the numbers right. We did just the opposite, and removed the secondary cats and the pipes had a bung for the 02 sensors. All works well and the Durametric shows all normal operation and readings.

This confuses me. Someone correct me if I'm wrong, but the 02 sensors are only before and after the upstream cat, right? If you eliminated the downstream cat (what you refer to as the secondary cat--the ones back by the muffler, right?), why would you change anything with the 02 sensors?

I haven't had a chance yet to read the Mike Focke link you sent (thanks for that). I will...maybe that'll make it clear.

[ttmedical]

Originally Posted by itsnotanova

I also used the foulers on my exhaust system after installing a 3.4 with headers and cat deletes. I would get a CEL every so often and have to erase the code to get the light to go away. It was always the left rear O2 sensor. I even changed out the rear sensors hoping that would help. I ended up taking my box to a friend who threw a ROW tune on it and I haven't had a light since. ROW tune doesn't care about the rear O2 sensors

Anyway you could point me in the direction of your friend? I'm at wits end with first getting P0430 codes for 2+ years and then with some finagling and extenders now intermittently getting P0160 for a year. I just hate that little check engine light for these issues and want it gone!

I'd really appreciate either your friend or anyone you may know in Houston who has the ROW flash capability. Thanks Woody!

P.S. Wife and I may be taking a roadtrip to hill country and we hope to stop by your shop. Hope to meet you there!