ECU "relearning"? - Subaru WRX Forum
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post #1 of 21 Old 11-24-2009, 09:51 AM Thread Starter
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ECU "relearning"?

I swapped out headlight bulbs Saturday which involved taking out the battery. I only drove the car about 3 miles after that Saturday evening to check out the new lights and buy gas. Did not drive it at all Sunday. Yesterday I drove to work, seemed normal on the morning commute, fairly tame in the rain but one high speed pass which seemed fine. Yesterday afternoon I was running a couple errands and it seemed soft on the low end, like slower to pull from around 2 grand up to 3 but then real quick from 3 on up, even to redline a few times. I logged most of the drive home on the AP and hit 14.3 lb of boost on one spirited acceleration, not what I would consider WOT, though. Still seemed that way on the way in to the gym and work this morning. I can see the revs climb, but it seems like it's not building boost, then whoosh, away it goes. No CEL, no funny noises.

This is an 06 WRX with a VF39 and supporting mods, Clark Turner e-tune, 4eat, just turned over 30k miles. It's only been 65 miles since I took the battery out. My thinking is this: either all of a sudden something has come loose and I've developed a vacuum leak, or my tranny has all of a sudden started slipping, or my ECU is relearning after I disconnected my battery. I recall that after I went to stage 1 and then stage 2 that it just seemed to get better as I drove it, although I don't recall that quite as markedly when I did the VF39 swap. So does this sound like it's just the ECU and all will be swell in a couple more days, or do I need to call my friendly mech and start trouble shooting?
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post #2 of 21 Old 11-24-2009, 11:17 AM
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I don't think it's anything drastic. The ECU naturally adjusts to your driving style. I notice this every time I get in my buddy's STi. I can barely drive the thing for like 3 blocks until it realizes I actually use the gas petal unlike him. Then it's happy. I think you just hadn't gotten on it in a while since it was wet and when you did, it wasn't sure you really wanted to. Go out and beat on it, it'll remember that you like it that way

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post #3 of 21 Old 11-24-2009, 11:22 AM Thread Starter
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Thanks, that makes me feel better. I will go out and drive it like it's supposed to be driven, then, and see if it gets happy again.
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post #4 of 21 Old 11-30-2009, 08:32 PM Thread Starter
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Okay, it's been a week and a half and it still doesn't feel right. I called my mech tonight and described it and he said it sounded like I had lost my reflash; the thought had entered my mind but since it wasn't a real time flash I dismissed it. Just for grins I reflashed my VF39 map and then took it out and beat on it. I made several WOT runs and maxxed out at 12.9 lb, so there's definitely a problem. I called him back and he said it could be 1) a voltage/ground issue and to clean my terminals real well or 2) a dirty MAFS from my filter. It's an Accel Cool Blue and I'm pretty sure it's preoiled, but it didn't seem near as sticky as the K&Ns I've used on my bikes. I know in the Boxster world people who used K&Ns were forever having MAFS issues but I hadn't seen that on the Subie boards.

So, does anyone have experience with rapid onset boost loss because of cruddy terminals or a dirty MAFS? This sucks majorly.
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post #5 of 21 Old 12-02-2009, 12:50 PM
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You using an AP to flash it ?

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post #6 of 21 Old 12-02-2009, 12:52 PM Thread Starter
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Yeah. When I reflashed it only took about 2 seconds so I'm pretty sure the map didn't get erased when I disconnected the battery.
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post #7 of 21 Old 12-02-2009, 12:54 PM Thread Starter
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I also tightened all the hose clamps last night and checked for loose hoses, nada. I took it out after that and logged some WOT runs and maxed at 11.5 lb, so I'm guessing it's actually a vacuum leak somewhere that is getting progressively worse. How would I locate a small vacuum leak?
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post #8 of 21 Old 12-02-2009, 01:57 PM
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MAF sensor crapping out, MAF sensor dirty, uppipe gasket leak, turbo fried usually due to oil starvation, compression starting to degrade (bye bye motor). My thoughts.

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post #9 of 21 Old 12-02-2009, 02:03 PM Thread Starter
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Stop thinking thoughts like "bye bye motor". It only has 30k miles on it. I cleaned the MAFS last night after the last run I logged. I didn't log this morning on the way to the gym which is when I can make my WOT runs. Between the gym and the office in stop and go traffic I did log and think I might have seen 6 lb, but there's nowhere on the morning commute to really mash the gas. Maybe tonight on the way home.
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post #10 of 21 Old 12-02-2009, 02:09 PM
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Eh, I kind of listed that in order of likihood. Good luck.

Oh, and I'm kind of leaving out the "your tuner's an idiot" answer but it's also possible. No disrespect intended.

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post #11 of 21 Old 12-02-2009, 02:20 PM
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You sure you are doing a "reflash" as opposed to a realtime flash ?

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post #12 of 21 Old 12-02-2009, 02:21 PM Thread Starter
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Positive.
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post #13 of 21 Old 12-02-2009, 02:52 PM
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I'd bet on a vacuum leak.... Have you played with the TMIC lately or maybe the BPV?

Paul
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post #14 of 21 Old 12-02-2009, 02:56 PM Thread Starter
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No. When I replaced my headlight bulbs I removed the battery and the intake scoop, but didn't touch the IC or the BPV. As a side note, the BPV hose is partially mashed by the throttle, which is apparently pretty common with the Gimmick inlet hose. I thought that might have the potential to cause some spiking, but it's been that way since we did the turbo swap a couple of months ago.
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post #15 of 21 Old 12-09-2009, 09:05 PM Thread Starter
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Okay, problem solved. I finally got a chance to take off the IC and heat shield and found that the actuator arm had come loose from the wastegate. New circlip and all is right with the world.
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