fishbone Posted February 14, 2014 Share Posted February 14, 2014 Took the car on the freeway, cruise at 75 stumble is very subtle, almost imperceptible. AF correction is staying within +- 10%, mostly around 5% or so, with some spikes. Damn, I was afraid of this kind of thing, chasing who knows what problem. I'm wanting to swap the MAF with a known good working one. Link to comment Share on other sites More sharing options...
snow05gtRI Posted February 14, 2014 Share Posted February 14, 2014 any thought about wheel speed sensors? (just seeing this thread for the first time, will go back and read the 9 pages) Link to comment Share on other sites More sharing options...
fishbone Posted February 14, 2014 Share Posted February 14, 2014 Currently the issue appears to be related to the amount of A/F Correction taking place, which indicates it has nothing to do with the wheel speed sensors. I'm still waiting to find out from those that know these things what, if any, amount of AF Correction is expected to be normal. I'm pretty sure spikes in the maximum possible corrections are not normal. Link to comment Share on other sites More sharing options...
Brian3676 Posted February 14, 2014 Share Posted February 14, 2014 I have not read this entire thread, but have you done a basic boost leak test? If so, have you maybe considered a smoke test? At a point sometimes it's cheaper to pay for a diag then throw parts at it. And yes a MAF can be clean but still bad. My MAF was bad, had 83k miles on it. Caused my af correction to jump all over and afr to always be off Link to comment Share on other sites More sharing options...
fishbone Posted February 15, 2014 Share Posted February 15, 2014 I'd rather buy a MAF and have it turn out to not be the issue than pay half the price of a MAF for a boost leak test. If I am wrong about the MAF at least I have a new MAF, the current one I have already has 7 years/110K miles on it and I distinctly remember a year ago a friend that was riding shotgun and watching ROMRaider did say that my MAF readings were bouncing around and the thought it was rather odd. Is there a way I can troubleshoot the MAF and rule it out? Link to comment Share on other sites More sharing options...
fishbone Posted February 15, 2014 Share Posted February 15, 2014 I started digging into what exactly A/F Correction #1 is based off and according to Cobb: https://static.cobbtuning.com/cobbtuningweb/site/support/accesstuner/monitor_definitions/Subaru_Monitor_List.pdf A/F Correction #1 -> Short-term (immediate) fueling correction in closed loop based on input from the front oxygen sensor. This is a percentage correction of the injector pulse width base. Positive values indicate fuel is being added as a result of the correction. Negative values indicate fuel is being removed ... but I replaced the front O2 sensor! Argh! Maybe what I am seeing in the correction range is normal and I am hunting the wrong gremlin? Link to comment Share on other sites More sharing options...
jeffy2.5xt Posted February 15, 2014 Share Posted February 15, 2014 another thought that recently popped into my head on this issue that will probably just send people into another fit of diagnosing random stuff, lol. how does the cruise control actually work on these? i havent taken the time to look myself. but if this a consistent only while using cruise at a certain rpm maybe it has something to do with a dead spot in the rheostat if that is the operating mechanism of the cruise. if it gets used at the same location too often the contact points could become worn or corroded? for lack of a better word. ive seen it happen on other rheostatic type switches for ac controls and things like that. just a thought. Link to comment Share on other sites More sharing options...
fishbone Posted February 15, 2014 Share Posted February 15, 2014 Cruise control is entirely controlled by the ECU which gets input from the other sensors involved. There is no separate external unit. I opened a thread in the Tuning section hoping that it gets exposure on the software side http://legacygt.com/forums/showthread.php/stumble-cruise-control-221051.html Link to comment Share on other sites More sharing options...
firehawk618 Posted February 15, 2014 Author Share Posted February 15, 2014 There is no sense in going down rabbit holes, that only compounds the issue and does nothing to actually lead to a resolution. We all know it could be a crapload of things responsible for it, so what we have to do is make an effort to narrow it down to the most likely resolution. I've had air leaks before, I know how the car reacts. The turbo inlet has been inspected and looks as if it's got 40K miles on it, not 100K. Is every stumbling issue caused by a flaky O2 sensor? Nobody is saying that. Right now for those of us that have chosen that avenue to tackle the issue have done so because that's where the evidence suggests needs to be done. My sensor should be here today and I hope I can tackle it tomorrow and come back with results. f1anatic, what sensor did you order? Did you use the OEM part # that's been referenced to here? How does your car drive now? Have you gotten a chance to look at A/F Correction? Is it steady? I looked at mine yesterday again and yep, it is all over the place, literally jumps from the max negative correction possible into the max positive within a fraction of a second. I am tempted to blame Marvel Mystery Oil which I have started to add to the fuel about 2 months ago. I believe it was the straw that broke the camel's back. It certainly fits with the timing if it turns out my O2 sensor is the culprit. I have already posted my results after o2 change. 10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned. SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC. Best 0-60: 4.651 by AP 1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission. Link to comment Share on other sites More sharing options...
firehawk618 Posted February 15, 2014 Author Share Posted February 15, 2014 Fishbone, did you read all the posts here? I just replaced my MAF with a new one. ZERO change. Yes it was a cheap Ebay one. I didn't mind spending 20 bucks to confirm or rule it out. Absolutely ZERO change. Old stock one is back on the car now. Someone else is talking about o2 sensor. Again, I already did this and in my situation NO CHANGE. I have the ever so subtle stumbe. Are you guys experiencing a jarring type stumble? Mines just a very light stuttering type. 10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned. SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC. Best 0-60: 4.651 by AP 1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission. Link to comment Share on other sites More sharing options...
fishbone Posted February 15, 2014 Share Posted February 15, 2014 Yep, same as you. Have you looked at AF Correction? Curious what you are seeing Link to comment Share on other sites More sharing options...
kzr750r1 Posted February 17, 2014 Share Posted February 17, 2014 Fish what AF correctin are you looking at? On the AP I see two before the monitor list goes to the learning set. Link to comment Share on other sites More sharing options...
f1anatic Posted February 17, 2014 Share Posted February 17, 2014 Alright, here's my experience. I wanted to get a log going on Saturday BUT after sitting out for a week, the battery was so discharged so I had to jump start the car. And due to the low battery voltage, the CarPC would not start. NOTE: in early January I had another problem with the car- main engine pulley disintegrated and the battery died for lack of charging. Since I do not drive the car during the week and the cold weather, it eventually died again.' Having jump-started the car, I took wife to the mall and I idled around. I am pleased to report that driving like a jackass in 2nd, 3rd and 4th gears on cruise control at speeds which kept my RPM around 3000 (higher revs for the alternator to hopefully charge my battery faster), my car had no more symptoms. I still plan on data logging but for now the CarPC doesn't work. I did pull the fuse but that did not work. Link to comment Share on other sites More sharing options...
fishbone Posted February 17, 2014 Share Posted February 17, 2014 Fish what AF correctin are you looking at? On the AP I see two before the monitor list goes to the learning set. A/F Correction 1 Here's another thought I had. Would toe/camber issues cause this sort of thing? Maybe the car is feeling resistance and is pushing against it constantly. I had to replace a set of tires just last week, the very inside edge was chewed up bad. I'm scheduled for an alignment tomorrow. I had swapped to Konis and Epic springs last year and I guess they either botched the alignment or the springs settled and I hadn't noticed Link to comment Share on other sites More sharing options...
rob-2 Posted February 17, 2014 Share Posted February 17, 2014 My Alignment is spot on so I don't think it's that. I am suspecting is the fuel pump. Link to comment Share on other sites More sharing options...
fishbone Posted February 17, 2014 Share Posted February 17, 2014 Decided to pull another LV. Looks like I have a leak. Based on the values, does it look pre or post turbo? Sucking the most air at idle. Usually my AF ranges are within 3% corrections, pulling fuel. Link to comment Share on other sites More sharing options...
rob-2 Posted February 17, 2014 Share Posted February 17, 2014 Go spray around with carb cleaner to see if you can find it. I've not been able to find a leak on my car. Link to comment Share on other sites More sharing options...
fishbone Posted February 17, 2014 Share Posted February 17, 2014 I called a local shop to see if I could schedule something and have them pressurize the intake and do a smoke test too and the guy suggested the same thing. So I already like them for the fact they didn't jump on the opportunity to charge me. Do I get the flammable or non flammable type? Link to comment Share on other sites More sharing options...
rob-2 Posted February 17, 2014 Share Posted February 17, 2014 I called a local shop to see if I could schedule something and have them pressurize the intake and do a smoke test too and the guy suggested the same thing. So I already like them for the fact they didn't jump on the opportunity to charge me. Do I get the flammable or non flammable type? Didn't know there were two options. My carb cleaner must be flammable. Link to comment Share on other sites More sharing options...
fishbone Posted February 17, 2014 Share Posted February 17, 2014 If carb cleaner test fails I will still have them pressurize the intake to rule out incompetence on my behalf, and then go from there. I have no regrets about having swapped the front O2 sensor that did not need to. It was old so at least now I have reassurance I've got a good working one. Link to comment Share on other sites More sharing options...
evil03mustang Posted February 17, 2014 Share Posted February 17, 2014 I need to leak-test my pile of shit, too. Its fuel trims are high on crack. Link to comment Share on other sites More sharing options...
rob-2 Posted February 17, 2014 Share Posted February 17, 2014 If carb cleaner test fails I will still have them pressurize the intake to rule out incompetence on my behalf, and then go from there. I have no regrets about having swapped the front O2 sensor that did not need to. It was old so at least now I have reassurance I've got a good working one. well I'm interested to know what you find. Having my motor rebuilt, retuned and inspected 3 times during that time. All leaks were found, all LV and tuning logs reviewed. Yet I cannot resolve this problem. I'm almost leaning towards it being the 'feel' of the H4 motor under load and low RPM. It has a great dead spot then an I4 would have. Link to comment Share on other sites More sharing options...
fishbone Posted February 17, 2014 Share Posted February 17, 2014 I looked at a LV from May of last year and the A/F Learning is under 5% on the negative side. One thing I did not watch while cruising was boost. I wonder if what happens is when the throttle is blipped the car starts tickling boost threshold so the leak goes away which causes the car to back off the throttle and then the unmetered air starts getting sucked in again, rinse and repeat. Link to comment Share on other sites More sharing options...
rob-2 Posted February 17, 2014 Share Posted February 17, 2014 I looked at a LV from May of last year and the A/F Learning is under 5% on the negative side. One thing I did not watch while cruising was boost. I wonder if what happens is when the throttle is blipped the car starts tickling boost threshold so the leak goes away which causes the car to back off the throttle and then the unmetered air starts getting sucked in again, rinse and repeat. Well I can duplicate this without being in a cruise. Also no metrics I could pull on romraider would show me what was going on. Link to comment Share on other sites More sharing options...
fishbone Posted February 17, 2014 Share Posted February 17, 2014 Can you post a Learning View? And by the way when I reset the ECU and took the car out for a drive to see if replacing the O2 sensor took care of the issue, I was registering -6 degrees of knock correction just dragging around town. It went completely away once the ECU started enriching to adjust for whatever is causing it to do so. So the car was definitely running leaner than it was supposed to which seems to have led to some very low load repeated knock, about 4 events. Link to comment Share on other sites More sharing options...
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