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  #13  
Old 03-24-2011, 12:45 AM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

Getting slow o2 sensor response with long tubes is a common problem on all FI'd vehicles. The problem lies in the loss of heat from the thinner walled tubing used in headers.

I know in the Mustang community we will commonly relocate the sensor to a point much closer to the head. Usually within 12-14 inches of the port exit, and just pick one tube. Yes you don't get a reading from all cylnders but on a modern engine you can be pretty sure that they are all performing very similarly. Also you can use header wrap to hold the heat in, which may help. That is unless you're using ceramic coated headers, then there's no benefit.
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Old 03-24-2011, 10:32 AM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

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Originally Posted by jeepgcoman View Post
Rose City, do you know what codes are thrown with the long tubes?
P0420/0430 are common.

P0133 and P0153 also come up.
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Old 03-24-2011, 01:57 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

Those codes are all related to O2 sensors and catalytic converter effectiveness. DTC's P0133 and P0153 are showing the front sensors to be slow in their response. DTC's P0420 and P0430, while addressing catalyst efficiency, could be caused by defective rear (behind the converter) sensors. The first thing I'd do is try to determine the age and brand of all of the sensors. If unable to determine that (and even if I could), I'd start by replacing all 4 sensors (~$120), with only NTK brand, and then reset all DTC's, both current and historical. I have read, and my personal experience has indicated that the Bosch sensors, in Chrysler products, are too slow to warm up and respond. Don't know about any other brand, but I do know that the NTK's work great. Anyway, now I am 99% sure that all sensors are working as advertised. If I still get a light, or lights, I am going to start looking at wiring, foreign contamination around the wiring or connections that may affect the sensor venting system, exhaust leaks (even very minor), or bad cats., depending on the code(s). Any exhaust leak will cause bogus signals to be sent to the PCM, possibly triggering a code. Because the sensors "breathe" through the wiring and connectors, it wouldn't take much to cause a problem. Again, new sensors and clean vehicle side connectors should negate that possiblity.

I still really can't see why just installing long tube headers should cause any problem, except maybe if poor connections were made when splicing the aft sensor extensions. If the system is leak free and there are sensors in front and rear of good converters it should work. The sensors and cats. don't know the difference. They're all just measuring and dealing with oxygen content in the exhaust gases.

What are the folks with long tubes doing about the EGR system? Do most of them have it shut off with a DS CMR tune, or are they living with the MIL? I know on the early LX's, the DS tuner had a menu item so the user could shut the EGR off. Because it was part of the emission system they ended up removing that menu item. I know CMR tunes aren't cheap, so addressing that could really cost some $$$.
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  #16  
Old 04-10-2011, 02:21 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

Are the o2 sensors location specific? IE up stream/ down stream? was looking on summit and they have 2 ntk's but one shows front and rear,the other shows left front
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  #17  
Old 04-10-2011, 08:08 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

great thread...+rep!

Did any of your research discuss the impact of CMR/aftermarket tunes and o2 sensors? I am intermittently getting P013A code (see thread below) and think they are related as the code will go away with a re-write of the tune and/or going stock. I do have some serious issues with my intake so I am in the process of getting a BT catch can, cleaning out the intake with seafoam and will be replacing pcv and oil after that. I could not believe how dirty my TB blade was, and that was only after 22k miles in Southern Cali weather

http://jeepgarage.org/showthread.php?t=18883
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Old 04-10-2011, 09:44 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

4.whoa, the fronts (1/1 and 2/1) are the same number and the rears (1/2 and 2/2) are a different number. I don't know why the difference, as they are basically supposed to work the same way.

Interesting, 08Hemi! No, I never found anything in my research that addressed aftermarket tunes. I've used both the DS and SC tunes on both my Hemi's and have never had a problem. Now, a CMR tune may be different since they may make significant changes to things not covered in the regular tunes. Add to that, the tune is only as good as the tuner.....how knowledgeable he is, and how familiar he is with the Hemi engine. Do you currently have a DS CMR tune on yours? Have you done any other mods to the engine or exhaust? Have you had the cats. checked? If you have a CMR, after checking all the normal stuff (leaks, loose wires, contamination, etc.) I think I'd take it back to the CMR tuner and have them see if they can find something they may have done that could cause it. Next, I'd probably take it to a muffler shop and have them check for leaks. Again, pay attention to the cats., as the code you're getting is for the "after the cat." sensor. (Hope either of those would cost little or no $$$) I've heard that some folks have had cracked exhaust manifolds but, I believe most are able to hear them when they're bad.

One thing to do if you have a CMR tune, if you aready haven't done so is to download it to your computer, so you don't loose it. Once you go back to stock it's gone unless you've saved it. If you've spent some good $$$ to get it done, I don't think you'd want to loose it....but then again, if it's causing the problem, maybe so. If it is causing your problem, they should fix it for free, IMO.

After you've checked all the "easy", low/no cost stuff I'd probably invest in a new rear sensor. If you have ~60K on it, you may want to consider changing them all like I did. My thought is that if one is bad (at that mileage) they're probably all not that far behind....plus I had one other (both were fronts by the way) that was sluggish.

Good luck and please let us know what you find.
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  #19  
Old 04-11-2011, 12:48 AM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

Johan...he works at DS and I def have them backed-up in my email and computer! IDK if there is an actual relation, but it just seems fishy to me because this has happened 3 or 4 times now and the sensors are not bad and to the best of my knowledge I do not have a leak...I uploaded a new cmr today and the code is gone and has yet to come back...so we shall see!
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Old 04-11-2011, 06:09 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

Update: Dealer's Service Manager is suggesting that Chrysler open up the limits for O2 Sensor "slow response" DTC that I get regularly. It varies from side-to-side and sometimes shows as a catalytic converter low efficiency DTC. My HEMI and the Durango they are working with seem to have the same issue. After a while, the O2 sensor does not follow the alternating square wave pattern while the engine is running. Seems to go to sleep, then the code sets.

Confirmed that the dealer only uses MOPAR O2 sensors. All 4 O2 sensor and both catalytic converters are ~4K miles old.

The limits are embedded in the PCM software and can't be revised by the dealers. Is this a capability of any of the tuners? I would be interested in relaxing the O2 sensor response time, but nothing else initially.
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Old 04-11-2011, 06:23 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

^^ Great question...anybody know? I am sending Johan an email now...
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Old 04-11-2011, 06:44 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

That would certainly help, but why is it happening to a few and not the masses? Seems like they're not fixing the problem, just masking it because they don't know they answers. I guess pulling the MIL bulb would fix it too.....at least some of it. Kind of like the same thing, at least to me.

Just thinking out loud.....wonder what would happen if they switched some of the suspect components (PCM, Sensors, etc.) between a known good running vehicle and yours? I know they'd have to reprogram the VIN's of the PCM to get it to work on another vehicle, but they should be able to do that with their Starscan tool. Maybe that would narrow it down between parts vs. vehicle wiring harnesses, etc. i.e. Your stuff works fine on another vehicle, or the good stuff off the "good" vehicle doesn't work on yours??? Thoughts, anyone??
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Old 04-11-2011, 07:42 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

Quote:
Originally Posted by jeepgcoman View Post
..Just thinking out loud.....wonder what would happen if they switched some of the suspect components (PCM, Sensors, etc.) between a known good running vehicle and yours? I know they'd have to reprogram the VIN's of the PCM to get it to work on another vehicle, but they should be able to do that with their Starscan tool. Maybe that would narrow it down between parts vs. vehicle wiring harnesses, etc. i.e. Your stuff works fine on another vehicle, or the good stuff off the "good" vehicle doesn't work on yours??? Thoughts, anyone??
At least for the Durango, the dealer did change out the PCM and the symptoms continued. On mine, no PCM change and the symptoms persisted. Other components (exhaust manifolds, O2 sensors, and cats) changed on both engines. Not an answer, just another data point.

Because it's so intermittent, I still lean towards an erratic electronic or sensor issue. Even now, when it's working, MDS is super-sensitive to load changes and the engine power is not there. There is no correlation between bumps or signals when on the flight recorder.

By the way, I don't have a MIL anymore.....it's an "Engine Running Light", 'cause that's when it's illuminated.
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Old 04-11-2011, 09:43 PM
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Re: Oxygen Sensors and Their Role in Engine Management--A Primer

"By the way, I don't have a MIL anymore.....it's an "Engine Running Light", 'cause that's when it's illuminated. "

Good one, Walt.
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