Tehnation Posted December 24, 2021 Share Posted December 24, 2021 So I unplug my maf and the car suddenly runs fine, but when I plug it in it falls on its face when it hits boost. I know this means something but don't know what, little help!? Is this a tune thing or a mechanical thing? Link to comment Share on other sites More sharing options...
Pleides Posted December 24, 2021 Share Posted December 24, 2021 I hate to sound condescending, but have you replaced the MAF sensor? The car being run in open-loop with the MAF disconnected also limits boost (and I believe retards timing a bit). You may have an issue with fuel or a vacuum leak that becomes more prominent when hitting full boost. Link to comment Share on other sites More sharing options...
Tehnation Posted December 24, 2021 Author Share Posted December 24, 2021 (edited) Brand new Maf (Denso 197-6040), brand new maf connector pigtail, maf has less than 100 miles on it. Edited December 24, 2021 by Tehnation Link to comment Share on other sites More sharing options...
Tehnation Posted December 24, 2021 Author Share Posted December 24, 2021 Also the current tune is mild at best, it was made for me to break in the motor, so the tune isn't for maximum power/boost at all. I'm also running BC stage 3 cams, which is making this rebuild a bit tricky because its not a common mod. Link to comment Share on other sites More sharing options...
dwmccauley01 Posted December 24, 2021 Share Posted December 24, 2021 (edited) Fueling? I have not run without the maf but assuming it will still add correction it may be pulling or adding the maximum correction which could pull the fueling into a more ideal range maybe? I'm not exactly sure what the ecu does when no maf is connected. Edited December 24, 2021 by dwmccauley01 Link to comment Share on other sites More sharing options...
Tehnation Posted December 24, 2021 Author Share Posted December 24, 2021 lol neither do I! I know my fueling stuff is good , pump, fpr, injectors etc. All new, double and triple checked. Link to comment Share on other sites More sharing options...
whitexc Posted December 24, 2021 Share Posted December 24, 2021 ^^^He may likely be referring to ECU fueling. Either the sensor is bad or you have an air leak, causing the good sensors reading to be skewed with the ECU attempting corrections. Sent from my SM-G996U using Tapatalk Link to comment Share on other sites More sharing options...
Tehnation Posted December 24, 2021 Author Share Posted December 24, 2021 Tried 2 different mafs and same thing. I don't think its the sensor, but could be if both the ones I have are duds. Link to comment Share on other sites More sharing options...
Infosecdad Posted December 25, 2021 Share Posted December 25, 2021 Double check that the new pigtail is correctly wired and all the pins are fully inserted? Link to comment Share on other sites More sharing options...
Marvick08GT Posted December 25, 2021 Share Posted December 25, 2021 How old is your primary O2? The primary A/F sensor and the MAF are what the Ecu use for closed loop operating. It getting better when disconnected, means the MAF or Primary O2 are the issue. Since you already replaced and rewired the plug, chances are the O2 is bad. Good luck and Merry Christmas! Link to comment Share on other sites More sharing options...
Tehnation Posted December 25, 2021 Author Share Posted December 25, 2021 (edited) I changed both the front and rear O2 sensors, both are new less than a 100 miles on them. I rewired it one wire at a time, so I am certain they are all correct order. Pins are good shape as well. Edited December 25, 2021 by Tehnation Link to comment Share on other sites More sharing options...
Tehnation Posted December 25, 2021 Author Share Posted December 25, 2021 Guess I gotta go to stealership monday and buy a new oem maf.... any way to test maf with a multimeter? And the O2 sensors? If not sensors than a vacuum leak? But unplugging makes it run better not worse, so not a vacuum leak?? I duno MERRY CHRISTMAS, HAPPY HOLIDAYS!!! Link to comment Share on other sites More sharing options...
dwmccauley01 Posted December 25, 2021 Share Posted December 25, 2021 What does the maf read at idle? And is the intake stock? Sent from my motorola edge 5G UW (2021) using Tapatalk Link to comment Share on other sites More sharing options...
Tehnation Posted December 26, 2021 Author Share Posted December 26, 2021 grimmspeed intake. will have to check maf reading in the morning. Link to comment Share on other sites More sharing options...
Tehnation Posted December 26, 2021 Author Share Posted December 26, 2021 What does the maf read at idle? And is the intake stock? Sent from my motorola edge 5G UW (2021) using Tapatalk Says I am at about 10 g/s give or take .2 g/s and voltage is at like 1.5 something when I am at idle. Link to comment Share on other sites More sharing options...
Tehnation Posted December 26, 2021 Author Share Posted December 26, 2021 (edited) The a/f sensor are actually 1 or 2 of the O2 sensors? The A/F ratio from the ecu is pretty much in line with my seperate A/F ratio gauge from my wideband, the pillar gauge reads about .3 more consistently but the ecu and wideband move the same. What other sensors would bork my mojo when giving it some boost? Map? From what I have read, if the unplugged maf makes car run better its most likely not mechanical or ignition, more likely the feedback control system.... which is I think the sensor stuff. Anyone know more about this feedback system? I guess something is giving some bad data.... another damn sensor issue! My god I can't win with these sensors... This cel malfunction system is absolutely worthless lol.... Now I know why the electrical system on my benz is so complicated. Edited December 26, 2021 by Tehnation Link to comment Share on other sites More sharing options...
Tehnation Posted December 30, 2021 Author Share Posted December 30, 2021 So if you unplug the maf, does it ignore everything else or just the maf? Like if I unplug the O2 sensor will it ignore the maf? Link to comment Share on other sites More sharing options...
Max Capacity Posted December 30, 2021 Share Posted December 30, 2021 I asked google, https://www.google.com/search?q=what+happens+when+you+disconnect+the+maf+sensor&rlz=1C1OKWM_enUS906US906&oq=what+happens+when+you+unplug+the+MAF&aqs=chrome.2.69i57j0i512j0i22i30l2j0i390l3.23073j0j15&sourceid=chrome&ie=UTF-8 then asked about a 2005 subaru legacy, https://www.google.com/search?q=what+happens+when+you+disconnect+the+maf+sensor+2005+subaru+legacy&rlz=1C1OKWM_enUS906US906&sxsrf=AOaemvJSqwx36d7jP72GhZGGaipU8dXEOQ%3A1640874846560&ei=XsPNYY3WIc2bptQP-tmK0Ag&oq=what+happens+when+you+disconnect+the+maf+sensor+2005+subaru&gs_lcp=Cgdnd3Mtd2l6EAEYAjIFCCEQoAEyBQghEKABMgUIIRCgATIFCCEQoAEyBQghEKsCOgcIABBHELADOgYIABAWEB46BQgAEIYDOgUIABDNAjoICCEQFhAdEB5KBAhBGABKBAhGGABQ3ApY0Tlgg1VoAXACeACAAXmIAekJkgEDMy45mAEAoAEByAEIwAEB&sclient=gws-wiz 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Tehnation Posted December 30, 2021 Author Share Posted December 30, 2021 (edited) I mean does it only ignore the maf if the maf is unplugged, or are other sensors ignored as well. Google doesn't answer that! Unplugging the maf just lets u know that something is wrong with air, boost or vacuum leak I am assuming. Edited December 30, 2021 by Tehnation Link to comment Share on other sites More sharing options...
Max Capacity Posted December 30, 2021 Share Posted December 30, 2021 You might want to reach out to "covertrussian" or Dave at Cyro Tuning. m sprank may know too, PM them. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
killjoy323232 Posted January 5, 2022 Share Posted January 5, 2022 When I was trying to troubleshoot my MAP by leaving it unplugged, the ECU substitutes default values for load. It very well might do the same with the MAF (I'd have to double check the service manual for the exact failure mode/failsafe). I was running into something very similar when I was chasing what turned out to be a huge vacuum leak - it'd run like crap with the MAP plugged in, but run great unplugged. What happens if you leave the MAF plugged in, but unplug the MAP? Are you getting good boost/vac readings from the ECU itself? I don't know if any of that helps at all... Link to comment Share on other sites More sharing options...
Tehnation Posted January 5, 2022 Author Share Posted January 5, 2022 Ive been a little busy, but this is all new to me, especially this engine tuning stuff, so its hard to figure out if the issue is the tune or mechanical. I went back to the first tune I had where it was leaning out until I got a cel. It doesn't have any hesitation at all and drives normally. The new tune I got to try and correct that lean issue seems to be cutting out as soon as the AFR hits 11. something, like it won't go lower than 11.x and then the car just bucks and hesitates. It works fine however when I unplug the maf. One tune runs lean and the other can't hit an afr lower than 11. I haven't done a new log with new intake manifold gaskets for either tune, so I will see whats going on there. I also installed a new oem maf, and ordered a new Grimmspeed air filter, the one I have seems dried up and deteriorated. Haven't tried messing with the MAP. Where was your vacuum leak? Link to comment Share on other sites More sharing options...
Tehnation Posted January 5, 2022 Author Share Posted January 5, 2022 (edited) So, actually on either tune afr wont go lower than 11.14, but the 1st tune it doesn't turn to crap while on the newer tune all hell breaks loose. 1st tune does have some very slight hesitation at certain rpm, hardly noticeable, i'm thinking its just lagging or turbo needs to be adjusted. Anyone know what adjusting the wastegate actuator arm does? Heres a new log of the original tune with new maf, and new intake manifold gaskets. datalog19.csv Does it still look like a vacuum leak? Going to try the new tune and see if I get the same issue. Edited January 5, 2022 by Tehnation Link to comment Share on other sites More sharing options...
Tehnation Posted January 5, 2022 Author Share Posted January 5, 2022 (edited) Looks like 11-12 is a normal afr for wot with these cars. So that value is actually fine. So 1st tune is lean at 11afr and 2nd cuts out at 11afr. Edited January 5, 2022 by Tehnation Link to comment Share on other sites More sharing options...
rhino6303 Posted January 5, 2022 Share Posted January 5, 2022 So, actually on either tune afr wont go lower than 11.14, but the 1st tune it doesn't turn to crap while on the newer tune all hell breaks loose. 1st tune does have some very slight hesitation at certain rpm, hardly noticeable, i'm thinking its just lagging or turbo needs to be adjusted. Anyone know what adjusting the wastegate actuator arm does? Heres a new log of the original tune with new maf, and new intake manifold gaskets. [ATTACH]294711[/ATTACH] Does it still look like a vacuum leak? Going to try the new tune and see if I get the same issue.The stock afr doesn't read lower than 11.14 and doesn't have the precision for tuning open loop fueling for turbo vehicles (which is where a wideband sensor is used). Once you're in open loop, the stock sensor goes rich to 11.14 very quickly and is more like an on/off than usable values. Link to comment Share on other sites More sharing options...
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