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Old 10-01-2013, 12:49 PM   #1
nate_fisher
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Default running lean wot weird problem

So I am having a weird issue and I don't want to keep bothering my tuner all the time since we are friends so I thought I would post up and see what people think. Car is 2011 xt on e85 with walbro 465, id1000 and fuelab fpr (with gauge) 55 psi base. E85 is from the same gas station and tested.

It seems to go lean at wot and has happened before and at wot it creeps to 12.5 afr toward redline. The crazy thing is when we tune it is spot on every time around 11.8 but after a while it relearns and goes lean again. If I reflash my map it goes back to normal and actually runs rich until it relearns again. I am not to sure the time span as I don't go wot that often so I cant tell you exactly how long it takes to go lean again. Also when it goes lean it does not matter if I adjust the fpr it always stays the same.
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Old 10-01-2013, 12:52 PM   #2
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Have you checked for leaks already?
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Old 10-01-2013, 12:56 PM   #3
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Yeah no leaks boost and vacuum are normal.
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Old 10-01-2013, 12:58 PM   #4
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Also wouldn't a leak affect my afr even I reflashed the ecu?
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Old 10-01-2013, 01:10 PM   #5
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What does your fuel trim D range read when it goes lean?
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Old 10-01-2013, 01:39 PM   #6
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I will have to check why what should it read and what would be bad?
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Old 10-01-2013, 05:50 PM   #7
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Quote:
Originally Posted by nate_fisher View Post
I will have to check why what should it read and what would be bad?
The D range effects all of open loop. So if it was reading -7 for example, which is a perceived rich condition in that range, it would lean out open loop fueling ~.7 trying to "correct" the rich condition. That would make an 11.8 afr turn into 12.5. The reason why it is usually 11.8 after a reset is because the fuel trims are reset when the ECU is reset.

If this is what is going on, just have Ray dial in that maf scaling a little better in that range. Usually its from 40g/s up to where open loops starts, but you can make the D range whatever you would like. Some tuners set the D range high enough that you can't ever hit it in closed loop, therefore it will always read 0, and not change the open loop fueling.
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Old 10-01-2013, 05:53 PM   #8
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The D range effects all of open loop. So if it was reading -7 for example, which is a perceived rich condition in that range, it would lean out open loop fueling ~.7 trying to "correct" the rich condition. That would make an 11.8 afr turn into 12.5. The reason why it is usually 11.8 after a reset is because the fuel trims are reset when the ECU is reset.

If this is what is going on, just have Ray dial in that maf scaling a little better in that range. Usually its from 40g/s up to where open loops starts, but you can make the D range whatever you would like. Some tuners set the D range high enough that you can't ever hit it in closed loop, therefore it will always read 0, and not change the open loop fueling.
Most say +/- 5% is good for fuel trims..I like to keep the "D" range under 2% if I can, and usually a positive number, so that way it can only richen up the open loop fueling. Id rather it go from an 11.0 to a 10.7, than an 11.0 to an 11.3.
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Old 10-03-2013, 01:26 PM   #9
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Well it is still running rich after flashing the map again but I took a look and my learning D was at -.4 at wot.
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Old 10-03-2013, 03:30 PM   #10
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How long has it been since it was reset? It depends how often you drive in the D range actually. If it gets up to -5 and higher, that is probably what is causing it to lean out.
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Old 10-03-2013, 05:36 PM   #11
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It has only been a couple days but I have only put 20 miles on it if that much. How long does it take to re learn usually?
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Old 10-03-2013, 05:46 PM   #12
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I would drive at least a full tank. It really depends on how much you hit that particular airflow range. If you don't boost, it will stay at zero. The difference in the E85 content from tank to tank can make your fuel trims wacky sometimes. Or I would just wait til you see it running 12.5ish air-fuel ratio again, then check what the D range says. If its low, than the problem must be something else.
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Old 10-03-2013, 06:26 PM   #13
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probably a MAF sensor on the way out.
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Old 10-03-2013, 09:28 PM   #14
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Quote:
Originally Posted by SkateAndDestroy View Post
I would drive at least a full tank. It really depends on how much you hit that particular airflow range. If you don't boost, it will stay at zero. The difference in the E85 content from tank to tank can make your fuel trims wacky sometimes. Or I would just wait til you see it running 12.5ish air-fuel ratio again, then check what the D range says. If its low, than the problem must be something else.
As mentioned, we definitely want to see what happens with the "D" range over time. If it does end up with a large negative value, that is indeed most likely the culprit.

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probably a MAF sensor on the way out.
Not probable on a 2011 vehicle unless the car already has 60K+ miles or has been operated in a very dirty climate. But it's a possibility

Cheers

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Old 10-04-2013, 06:19 AM   #15
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Not probable on a 2011 vehicle unless the car already has 60K+ miles or has been operated in a very dirty climate. But it's a possibility
ahhh missed that part! agreed not probable. swapping with a friend would be a quick test.

fpr or fuel pump are also possibles
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Old 10-04-2013, 12:41 PM   #16
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The fpr is new and it did it before that was installed. The pump is also almost new and while it was lean I swapped in a different pump and nothing changed. I also tried to raise the pressure but it would still go to 12.5 afr.

On another note I had a pretty big leak on my fuel pump housing gasket as it was installed wrong and was leaking out fuel when I filled up with gas. I put the gasket on correctly and it no longer leaks even though I broke one of the studs but there are still 6 left. Could that have anything to do with it, I don't really know if a evap leak in the tank would cause this issue or not? Since were on the subject does anyone have any suggestions on how to put a new stud on the tank since they are welded on and not changeable?
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Old 10-04-2013, 01:48 PM   #17
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It wouldn't be the pump or fpr because once the ECU is reset, the air fuels go back to normal. The pump/fpr don't care if they ecu is reset.
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Old 10-04-2013, 02:18 PM   #18
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i don't think it's time to rule out all mechanical issues though.

the only thing fuel related an ecu reset does it clear LTFTs.

can you force LTFTs to zero on the 32b ecus as you can on the 16s? basically still run closed loop but no learning.
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Old 10-04-2013, 05:53 PM   #19
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Quote:
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i don't think it's time to rule out all mechanical issues though.

the only thing fuel related an ecu reset does it clear LTFTs.

can you force LTFTs to zero on the 32b ecus as you can on the 16s? basically still run closed loop but no learning.
Yup, you can zero out the D learning range still.
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Old 10-05-2013, 07:07 PM   #20
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Well you were rite it started running lean again finally and sure enough my d learning was -12.3. So what does this mean exactly?
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Old 10-05-2013, 07:14 PM   #21
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Well you were rite it started running lean again finally and sure enough my d learning was -12.3. So what does this mean exactly?
Granted you have no leaks anywhere, Ray just has to do some maf scaling. Are the A,B,and C fuel trims fine? You want that D range as close to zero as possible so it doesn't effect your target air fuel range going into open loop fueling. If anything, you would want it to tend to be a positive value, that way your air fuel ratio would only end up getting richer which is safer.
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Old 10-05-2013, 07:19 PM   #22
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They were all in the negative range not as bad as the d but pretty bad. I don't believe I have any leaks but I will check it my vac stays jut fine and my boost levels are we're they always have been.
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Old 10-05-2013, 07:28 PM   #23
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He probably just needs to clean up the maf scaling a little then, no biggie. This is one of those times where having a wideband really pays off.
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Old 10-05-2013, 07:37 PM   #24
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Could it be that my maf is maxed out?
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Old 10-05-2013, 07:40 PM   #25
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Also what is your reading on your vac on your auto? If I'm in gear it's around 18hg if I am in park it's around 20hg and when I am driving around and let off it sinks to around 22 hg. I am pretty sure it's always been like that but just wanted to check.
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