A shop tells me that the o2 sensor (A/F ratio) in my Speed3 is slow to react and should be replaced. The OEM Mazda part is $500+. I can find them non-OEM replacements online starting at $40. Is there any reason that I should buy OEM and not one of the less expensive ones?
Feeling lucky?
This is the wideband sensor on the downpipe?
I took a stab and guessed that's a 2010. Rockauto has a NTK for $215. I'm betting that's OE. I would run it.
When I pulled the turbo on my 08 I removed the sensor and destroyed the threads while doing so. I guess it's common for that to happen with these. I think the trick was to crack it loose while everything was really hot. Just info
Crack it loose when COLD. They make oxygen sensor sockets with a hammer pad so you can whack it with a hammer. Stainless steel turns to taffy when it is hot and loves to gall.
I mean, sometimes you gotta do what you gotta do.
OE is probably Denso. I have never had fault with a Denso sensor. NTK is also very good...
I wouldn't say the $500 dealer part is necessary, but $40 sounds too good to be true. Denso, NTK, and Bosch are usually a safe bet...OTOH I had an experience with a Focus in the past where I couldn't get the damn CEL to stay off until I put an OEM sensor in.
So the more modern sensors have a lot in them- probably a WB sensor, which should make it north of $40. And it's likely to be a really fast light off sensor- so the heater is really robust.
A cheap sensor will be noted via the OBD system.
Speaking of which- do you have a check engine light? If not, the shop is blowing smoke and should be ignored. Even if it was slower than new, as long as the system is ok with it, leave it.
+1 for Denso/NTK/Bosch, any of those will work just as well as OEM.
Thanks for the replies so far.
Additional info: 2013 Speed, Cobb CAI and off the shelf tune. HPFP has not been upgraded yet. There is no CEL. I was just wondering if the slow to react F/A sensor could be the cause of what I'm feeling.
I brought it to a shop because of a weird hesitation that is worse now than when I bought the car 25k miles ago. It is most noticeable between 2500 and 3300rpm when I aggressively accelerate (heavy load), lift slightly, then quickly get back on the throttle. That being said, I can also feel it when driving more calmly (light load) in traffic. I'm not ruling out that this is caused by the Cobb tune, but since its getting worse, I'm not convinced it is the tune...yet. Once I upgrade the HPFP I'll look into a proper tune.
The car doesn't consume any oil (!), and the plugs have at least 25k miles on them and they look great.
myf16n said:A shop tells me that the o2 sensor (A/F ratio) in my Speed3 is slow to react and should be replaced. The OEM Mazda part is $500+. I can find them non-OEM replacements online starting at $40. Is there any reason that I should buy OEM and not one of the less expensive ones?
That listing is wrong. No way you buy an air fuel ratio sensor for $40, let alone one that functions.
OEM part number: L3CE-18-8G1
Thought I saw $40, now I see $56.
EDIT: When I declined (over the phone) to have the shop replace the 02 sensor, they didn't try to convince me to have them do the work, then when I picked up the car they took the time to point out where it was and that I could easily do it myself when I'm ready to do so.
That made me think that they actually felt the o2 sensor was worth replacing.
Pete. (l33t FS) said:Crack it loose when COLD. They make oxygen sensor sockets with a hammer pad so you can whack it with a hammer. Stainless steel turns to taffy when it is hot and loves to gall.
I mean, sometimes you gotta do what you gotta do.
OE is probably Denso. I have never had fault with a Denso sensor. NTK is also very good...
I won't disagree with this advice. But I removed mine cold and it had definitely never been out before and it galled up something horrible. Google/forums say my experience is typical. The advice I saw was to crack it hot. Never tried it but just passing along info
Anyone know what is in a Cobb calibration? I'd really think that.
Given what has been done with the engine, I don't see a need for an upgraded pump- even using the calibration to its end capability, without major changes, the high pressure pump should be fine (unless is crap from Mazda). And unless you are using leaded fuel and/or only racing it, you are not going to age the O2 sensor significantly until past 150k miles. The system is designed and tuned around an aged set up anyway.
Which leads me to the calibration from Cobb. And I've rarely seen the aftermarket know how to do it *right*.
If you really want to see what's going on, find a way to record it via OBD. That will tell you a lot. Engine speed, load/map, main and secondary o2, pedal, and throttle is enough to figure a path of issues.
I recently bought a set of cheap no name chinese o2 because they were the only thing I could get before a trackday. They actually made the car run worse. The CL mode was basically unusable and the long term fuel trims were up at like +45% when I checked. Fortunately the OL mode still was fine. A couple days ago I got a set of Denso o2 for my car and it drives so much better. Fuel trims back to where you would expect. It was both banks on my car too. So either I got 2 defective sensors or they are alsolute garbage. And these are narrow band sensors that you'd think wouldn't be hard to get right.
alfadriver said:Anyone know what is in a Cobb calibration? I'd really think that.
Given what has been done with the engine, I don't see a need for an upgraded pump- even using the calibration to its end capability, without major changes, the high pressure pump should be fine (unless is crap from Mazda). And unless you are using leaded fuel and/or only racing it, you are not going to age the O2 sensor significantly until past 150k miles. The system is designed and tuned around an aged set up anyway.
Which leads me to the calibration from Cobb. And I've rarely seen the aftermarket know how to do it *right*.
If you really want to see what's going on, find a way to record it via OBD. That will tell you a lot. Engine speed, load/map, main and secondary o2, pedal, and throttle is enough to figure a path of issues.
The weird hesitation has been present since I bought the car with the Cobb CAI and tune previously installed by the PO. I'm sure that the Cobb tune is less than perfect, but I don't think that explains why the hesitation is getting worse / more pronounced.
The stock HPFP is universally recognized as a weak point, and the tuners I've spoken to do not advise tuning the car without upgrading the pump first. I might get away with it since I'm only looking to improve drive-ability and not adding power, but why risk it?
In reply to myf16n :
But so far, all you have done was a CAI, which may or may not actually do anything useful. So you don't need a hpfp, yet. And a drifting O2 sensor should not cause a tip in hesitation since it's rather slow in compensating even when new. If you took data, and there is a clear a/f issue, the fact that you can detect it tells you that the issue isn't the sensor- that's really why I suggest getting data via the OBD port.
FWIW, transients under 1 second are not dealt with using the O2 sensor- that all air calculation and transient fuel calculation.
If you just want to throw parts at it, that's fine. But the tools to really figure out what the issue is are cheap, too.
In reply to alfadriver :
I definitely do not want to throw parts and $ at it. I can certainly log data with the Accessport and will take a look at that. Interpreting that data is a whole different issue.
In reply to myf16n :
Log it, post the data. If you can plot it, time vs: engine speed, map/load, pedal, o2/short term fuel. Then post the graph and try to put a mark where you think it's hesitating.
For sure, I'll look at the data, and I'm sure others will be interested.
I can't process the data right now- won't have access to a computer for another week or so.
A stupid human trick I have is that if I think an O2 is skewed, I'll just unplug it and go for a drive. May need to reset long term fuel trims.
If it drives better, the O2 is probably on its way out. If it's worse but plugging the sensor back in, allowing it to go into fuel correction, makes it better again, then the O2 is probably okay.
It's rare to have an upstream sensor drift and not set catalyst codes or sensor codes. Cats don't work if you're not at stoich after all. (Unless it's a flat six Subaru, in which case it will just gleefully slam fuel trim one way or the other until it misfires... and then set misfire codes.)
What happens more often in that case is that the DOWNSTREAM sensor drifts, and the internal algorithms are biased to believe the downstream sensor is good and the upstream is bad, because the upstream sees more heat and thus is usually the first to go. "Hey the upstream says we're stoich but downstream is stuck at .2v.... we must be really lean and the upstream sensor is faulty! Set a code for the upstream sensor!"
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