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04-28-2018, 04:55 PM | #1 |
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Unplug the eccentric shaft sensor - what does it do?
2011 128i N51 6MT w/AA headers and BPC tune
I had headers installed a few months ago by a shop. Starting with the drive home from the shop, I've had this erratic idle which drops to about 400RPM, then shoots up to 8-900 and comes back. Occasionally it will stall when idling. I installed the BPC tune and it makes no difference, flashing back to stock gives me the exact same behavior. I've cleaned the MAF sensor and both VANOS solenoids, swapped the VANOS solenoids multiple times, and replaced the eccentric shaft sensor 1 month ago - none of these things helped. I reset all adaptations using INPA and the car drove perfect for 1 test drive, then the issues came back again. I've put ~500 miles on it since resetting adaptations with no change in behavior. There are no consistent codes to help me figure out what is causing this. Now the only piece of useful info I've got - if I unplug the eccentric shaft sensor, the car idles and drives perfectly just like before I did the headers. This tells me it is not a failing injector, plug or coil. I don't think it is a dead DISA motor/valve, since flashing back to stock has no effect, and the stock tune does not activate the DISA motors as far as I know. So, what gets disabled when I unplug the ESS? The entire VANOS and Valvetronic systems? The DISA motors? Anything else? Should I just reset adaptations again? |
04-29-2018, 08:39 AM | #2 |
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Had the same issue when I put my headers and AA tune on the car, I reset the adaptations and drove the car hard and drove it for about 100 miles and got a SES, cleared that SES and have been good since and put roughly ~3000 Miles since the flash
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05-01-2018, 06:43 AM | #3 |
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I do think this is a common problem, maybe the tuners can chime in?
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05-01-2018, 08:47 AM | #4 |
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Thanks for your responses. I've driven it pretty hard since resetting adaptations, but it does not seem to have much effect. Some drives, it is really not bad. Other drives, it is stalling out at red lights. Sometimes the beginning of a drive is fine and the end is bad, sometimes it's the reverse. In all cases, it drives great above 1500rpm. The reason I'm hesitant to reset adaptations again is because I've read it takes about 800 miles after a reset for the car to figure itself out. I'm already 500 miles in, and don't want to start over. At the same time, it's not improving and I'm not hearing about other peoples' cars stalling after a reset. The purpose of this thread is to narrow down to the mechanical components that could be failing.
Again, the car runs perfectly (though down on power slightly) with the eccentric shaft sensor unplugged. So this tells me that the plugs, coils, injectors, O2 sensors, and MAF are probably fine. If one of those were failing, I would expect that the car would run like shit even with the sensor unplugged. That leaves the Valvetronic, VANOS, or DISA components, cam position sensors, or crank sensor that I should check. Anything else? |
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05-04-2018, 05:22 AM | #5 |
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Well, since you stated that the problem started directly after installing headers, maybe the o2 sensors plugs were swapped when installing the header. once a shop swapped these on my car and it started misfiring on idle like a bad coil packs, when we swapped plugs of o2 sensor it ran fine.
Also when changing the ess, was the valvetronic inatalled fine ? Also sometimes when removing/installing valvetronic bmw recommends that the valvetronic needs to find its mechanical limits again, it can be done with a software or sometimes just turning ignition on after installing fixes it |
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05-05-2018, 10:16 AM | #6 |
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I checked the O2 sensors multiple times and they are not reversed. The car also runs fine when I reset adaptations (for 1 drive only), or unplug the eccentric shaft sensor. If either of those conditions causes the car to go into an open-loop scenario regarding the O2 sensor, then you might be right.
So I reset all the adaptations in INPA the other day and the car ran perfectly again. No misfires, no hesitation, no surging, nothing - just perfect. For one drive. Today I drove the car and it's back to the same old shit. Idle dropping from about 600 to 400, then shooting back up to 800, repeat. If I rev it up to 1200rpm it will jump up and down the same way - 1200, 1000, 1400, repeat. I am just about ready to sell this car. Absolutely ruined it by adding headers and the tune, and the whole point of doing the mods was to get better driveability, not power. What is the fucking point of the adaptations anyway? BMW couldn't make a car that just drives? Can adaptations be disabled in INPA? |
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05-05-2018, 11:33 AM | #7 | |
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05-05-2018, 12:40 PM | #8 | |
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I've reset all the adaptations. The first time, I individually reset everything from top to bottom in INPA. The next time, I used the 'reset all' button in INPA. I've also reset the throttle adaptation using the throttle pedal but it does nothing. Tuned for 93 and I use 93 from Shell, have never had a problem with this particular station with any of my cars. I double-checked the precat O2 sensors by swapping the plugs, and the car ran like shit and threw 4 misfire codes. |
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05-05-2018, 01:34 PM | #9 | ||
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I use to have a shit idle and i ran a fuel system cleaner and it seemed to work for me (no headers though)
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05-06-2018, 12:43 AM | #10 |
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When he flashed to stock, he had the same issue.. so it s not tune related. I have always wondered about the map sensor, i dont know if it could be the culprit.
It must be a sensor since it is running fine after resetting adaptation (so not injectors and not a vaccum leak).. i am wondering if an alpha n tune could solve this (bpc has one) |
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05-08-2018, 10:15 AM | #12 |
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Run some Techron Fuel System Cleaner through...it works like magic on the N52!
Drop it in an empty-ish tank, fill to one quarter, drive the wheels off the car, put more Techron in and fill it up all the way. It seems to be a cure-all for a poor-running N52 that doesn't seem to have any mechanical/electrical issues...
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05-08-2018, 11:40 AM | #13 |
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This is what google says:
The eccentric shaft position sensor is used as a feedback for the Valvetronic eccentric camshaft. The eccentric shaft is actuated by the Valvetronic motor and in return controls variable intake valve lift. The eccentric shaft sensor is mounted to the cylinder head beneath the valve cover.
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05-12-2018, 08:14 PM | #14 |
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I have had the EXACT same issue and I cannot figure out what it is. I have checked for vacuum leaks, cleaned the MAF, returned it multiple times and brought it back to the stock tune.
I don't really know what else to do next. I am going to change the spark plugs next as kind of a shot in the dark (yes I know the recommend mileage is 100k). BOL, keep us updated |
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05-13-2018, 04:50 AM | #15 |
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Let's focus on MAP for a bit, as the descriptions I've read online may point there. RealOEM calls this a differential pressure sensor which is different than a MAP sensor. A differential sensor is basically a vacuum sensor and should show zero at 0RPM, as there is no differential between the intake manifold and ambient with the engine off. With the engine running, I'd expect the reading to drop when throttle is opened and rise when throttle is closed.
In INPA, Saugrohrdruck (intake manifold pressure) shows zero with the car on but not running. With the car revving between 400 and 800 on its own, Saugrohrdruck hovers at 4-6kpa and doesn't really change much. I do think this sensor may be shot, but before I throw another $90 into the car, can anyone with INPA and a good running car check the readings for Saugrohrdruck and let me know what you're finding at idle and possibly when revving slightly? |
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05-13-2018, 06:14 PM | #16 | |
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Edit: Mines bouncing between 4-5 after idling for ~15min in my garage. Last edited by desertman123; 05-14-2018 at 02:43 PM.. |
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05-15-2018, 06:21 PM | #17 | |
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I played around some more today and think it is the MAF sensor. I've cleaned it twice with no effect so I'm going to replace it. My existing MAF is by Continental. FCPEuro has a Siemens/VDO sensor for $188, or Genuine for $299. Is this one of those cases where you really want Genuine or is VDO sufficient? |
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05-17-2018, 07:53 AM | #19 | |
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05-18-2018, 08:53 AM | #21 |
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I hope to god it works!
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05-19-2018, 12:45 PM | #22 |
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No dice. The new sensor is identical to the factory one and says Continental on it. I suppose VDO manufactures for Conti? Replaced sensor, car doesn't stumble quite as dramatically as before but still revs up and down the same way as before. I replaced MAF because I got a code stating the MAF value was implausibly high and it recurred 3 times. Also was seeing "HFM Sensor airmasse" at 0.00V but the new one still shows that.
I then got a secondary air system code for bank 2 (this is N51 don't forget). The check-valve is working, I pulled it off and blew through it in both directions and it didn't let exhaust back out to the pump. Also started the car with the valve removed and both banks were letting exhaust out of the ports so they are not blocked. With engine running, the checkvalve is not letting air out with the hose removed. I can turn the pump on with INPA and it runs, and is off when the car is running and warm. Okay so ruled out a secondary air failure. This would point to an O2 sensor failing, I think. I don't know how to interpret the values I'm seeing in INPA for lambda probes. I've read they should be between 0.3 and 0.9 volts. The green range in INPA for precat is 0 to 2.7, and mine are both jumping between 1.3 and 2.5. For postcat, the green range is 0 to 0.9 and both are around 0.43 and jump around a bit. Any thoughts on whether these values look normal? |
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