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Old 6th August 2008, 19:32   #191
wilsodh
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What exactly is behind the codes?

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Originally Posted by mfizzlenyc View Post
How bout those AE And AF codes ????? any one know what that means "air Fuel Adaptation"???
Ok, since I didn't get any bites, I'll take a fresh stab at this.

There are three players in the mix: 1) MAFs, 2) ECU, 3) pre-cat O2.

The MAFs send a voltage signal to the ECU conveying an indicated air flow. The ECU attempts to trim the fuel to the optimal stoichiometry. It then looks for feedback from the pre-cat O2 sensors.

Let's say your MAF is going bad...it is gunky and sending a voltage signal that is under-estimating the air flow. The ECU adds less fuel than optimal based innacurate information from the MAF. The O2 sensor reports 'lean', which doesn't line up with the ECU's input. The ECU then attempts to 'adapt' by trimming more fuel to bring the O2 sensor output closer to target.

If things get too out of wack (the ECU must make adaptations outside a certain specification or percentage), it trips an 'adaptation' code. It is also possible that one may see a 'Mass air flow plausibility' code indicating that the MAF readings don't make sense to the ECU.

The ECU's adaptations are both spontaneous and stored as a new baseline. I imagine this helps compensate for the particulars of the sensors and environmental factors. To reset adaptations, the battery must be disconnected for a period of time to clear capacitator charge.

Well, that's my primitive understanding. All - please feel free to add corrections or further clarification!

I'd love to see us all try and better understand what is behind many of our codes to really understand our beasts.

Dave
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Old 7th August 2008, 04:07   #192
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Quote:
Originally Posted by wilsodh View Post
...

Well, that's my primitive understanding. All - please feel free to add corrections or further clarification! ...
Hi Dave,

You pretty much have it down although I suspect the post-cat O2 sensors may also play a role.

With that said, the problem with that code is in trying to figure out which component has gone bad: MAF, O2, or injector, since really all that code is telling you is that the information it received from the 2 sensors (and reacted to using the injector) doesn't correlate in it's mind. It is also worth noting that this could easily be affected by any aftermarket DME software as well.

The biggest problem with cars these days is, not surprisingly, in the error codes. Nonsense like this is basically the same as "something is wrong but I don't know what". In my opinion there are 2 responses to a code such as "air fuel adaptation": a) replace the MAFS, O2 sensors, the injectors and finally the DME until the problem goes away, or b) ignore it until you get a different code. Personally, I'd got for b, but then I don't have a car that's supposed to make 7 gazillion horsepower

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Old 7th August 2008, 17:34   #193
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Thanks Doug. I was hoping you might chime in. You introduced injectors into the mix, which I didn't comprehend. Fortunately, clogged injectors seem to be an rather uncommon issue for us, presumably because most of us use good gas.

So let's look at two injector scenarios: underperforming (partially clogged) or 'dead' (fully occluded or some other mechanical malady).

I'm guessing a single under-performing injector may not impact the O2 signal too much. It might take multiple under-performing units to trip an adaptation code. What do you think? Any other codes come to mind that might point to this scenario?

Now if an injector is 'dead', would we anticipate a cylinder-specific 'misfire' code? Do we know what is behind the cylinder-specific 'fuel injector' codes (03, 04, 05, 1F, 20, 21, 22, 23)?

D
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Old 8th August 2008, 04:37   #194
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Quote:
Originally Posted by wilsodh View Post
Thanks Doug. I was hoping you might chime in. You introduced injectors into the mix, which I didn't comprehend.
I'm here to help - plus I gotta get my post count over 4K so I can be an expert in something

Ok, seriously -- I introduced injectors into the mix because they are the other half of the air/fuel mixture. Malfunctioning MAF's are a clear issue, and clearly the ECU can cause an issue with fuel if it is malfunctioning, but what if the ECU is ok and is just getting bad information about the amount of fuel being dispensed (much like the amount of air entering the engine with a bad MAF). It seems to me that a malfunctioning injector (perhaps that isn't the correct part - I'll check with some friends who are a bit more knowledgeable) could have the same effect as the MAF but from the other side.

Quote:
Fortunately, clogged injectors seem to be an rather uncommon issue for us, presumably because most of us use good gas.
True, but clogged is not the same as malfunctioning

Quote:
So let's look at two injector scenarios: underperforming (partially clogged) or 'dead' (fully occluded or some other mechanical malady).

I'm guessing a single under-performing injector may not impact the O2 signal too much. It might take multiple under-performing units to trip an adaptation code. What do you think? Any other codes come to mind that might point to this scenario?
I would think one severe malfunction or fully dead injector would trigger the issue - you're talking about a 25% increase in unburned oxygen suddenly making it's way to the O2 sensor.

Quote:
Now if an injector is 'dead', would we anticipate a cylinder-specific 'misfire' code? Do we know what is behind the cylinder-specific 'fuel injector' codes (03, 04, 05, 1F, 20, 21, 22, 23)?

D
I don't know for certain, but I would be willing to bet that the misfire codes are not triggered by a sensor measuring actual spark but rather a sensor that measures whether or not the coil discharged (and is therefore recharging as it should). This is pure conjecture on my part, but is based on the fact that I've never seen any sensors inside a cylinder and the only other thing attached to the plug is the coil.

As for the fuel injector codes, I'm afraid I don't have a clue, but I would expect a code for those as well.

Doug
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Old 8th August 2008, 13:46   #195
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Doug, I've got it figured out... if I have someone like you living nearby, I won't be forced into selling my car because it refuses to stop breaking no-kidding every single week. So here's the deal- you move into our huge guest room, complete with your own bathroom and all food and utilities providied... and in return all you have to do is keep my baby from falling apart! Watcha say?
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Old 10th August 2008, 02:55   #196
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Doug, I've got it figured out... if I have someone like you living nearby, I won't be forced into selling my car because it refuses to stop breaking no-kidding every single week. So here's the deal- you move into our huge guest room, complete with your own bathroom and all food and utilities providied... and in return all you have to do is keep my baby from falling apart! Watcha say?
I could, but I'm afraid I come with a bit of baggage - like a wife and 3 little girls ages 3 and under. I'm guessing you'd regret that deal about a week in

Always happy to help - if you're ever in New England you can stop by and I'll give your baby a once over!

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Old 10th August 2008, 06:45   #197
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Quote:
Originally Posted by DouglasABaker View Post
I could, but I'm afraid I come with a bit of baggage - like a wife and 3 little girls ages 3 and under. I'm guessing you'd regret that deal about a week in

Always happy to help - if you're ever in New England you can stop by and I'll give your baby a once over!

d-
Man, that's a whole chearleading squad right there... I don't know if my ears could handle that my friend. I swear I would drive to your house right now if I thought the thing would make it, but judging by the luck I'm having this year I doubt it would

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Old 11th August 2008, 03:06   #198
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Quote:
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Man, that's a whole chearleading squad right there... I don't know if my ears could handle that my friend. I swear I would drive to your house right now if I thought the thing would make it, but judging by the luck I'm having this year I doubt it would
It might get a bit loud at my house on occasion

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Old 12th August 2008, 22:05   #199
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Quote:
Originally Posted by DouglasABaker View Post
I don't know for certain, but I would be willing to bet that the misfire codes are not triggered by a sensor measuring actual spark but rather a sensor that measures whether or not the coil discharged (and is therefore recharging as it should). This is pure conjecture on my part, but is based on the fact that I've never seen any sensors inside a cylinder and the only other thing attached to the plug is the coil.

As for the fuel injector codes, I'm afraid I don't have a clue, but I would expect a code for those as well.

Doug
I've asked around, and all I get back is a 'misfire' code would be likely in the event of an injector failure. Fortunately, injector failures seem very uncommon in our cars. Leaky injectors are more common. Any luck with your buddies?

In any case, the initial topic was issues that could cause adaptation codes. In my beast (the s/c'd one), I get to watch the ECU adapt to funky signals via my A/F gauge. It is quite entertaining (I probably spend more time watching that gauge at times than is healthy). I was 99% certain I had a MAF problem watching my ECU struggle with apparently unstable input. This weekend, I swapped in new MAFs, and viola', spot-on fuel trimming and one happy uberbeast. And...another recurring adaptation code (along with a fuel control code). I have a fresh fuel pump and disconnected post-cat sensors. If I rule out MAFs, injectors, post-cat sensors (unless there is reason not to), I'm left with the ECU and the pre-cat sensors. If there is a pre-cat sensor issue, I would expect to see a related code...

Last edited by wilsodh; 13th August 2008 at 00:24.
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Old 13th August 2008, 04:31   #200
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Quote:
Originally Posted by wilsodh View Post
I've asked around, and all I get back is a 'misfire' code would be likely in the event of an injector failure. Fortunately, injector failures seem very uncommon in our cars. Leaky injectors are more common. Any luck with your buddies?
Nothing yet - but then I haven't been to Michigan yet this week to talk to them about it

Quote:
In any case, the initial topic was issues that could cause adaptation codes. In my beast (the s/c'd one), I get to watch the ECU adapt to funky signals via my A/F gauge. It is quite entertaining (I probably spend more time watching that gauge at times than is healthy). I was 99% certain I had a MAF problem watching my ECU struggle with apparently unstable input. This weekend, I swapped in new MAFs, and viola', spot-on fuel trimming and one happy uberbeast. And...another recurring adaptation code (along with a fuel control code). I have a fresh fuel pump and disconnected post-cat sensors. If I rule out MAFs, injectors, post-cat sensors (unless there is reason not to), I'm left with the ECU and the pre-cat sensors. If there is a pre-cat sensor issue, I would expect to see a related code...
I concur that I would expect a pre-cat sensor issue, but again, if you consider the case of the MAF it is entirely feasible that the code you are getting IS the pre-cat sensor fault. I know there is a specific code for them, but there is one for MAF's as well, so perhaps when the data it receives is only slightly out the DME triggers an adaptation code instead of a fault.

Consider this theory: What if the range of "ok" values for the pre-cat O2 sensor for a normally aspirated vehicle is too wide for a turbocharged one? If it were, then when the O2 sensor provided values at the outskirts of the "normal" range your DME might not be able to adapt and therefore would send an adaptation error instead of an O2 fault code?

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