Extreme shaking on idle (idle logs included), need input

[Seaneezy]

Hi all,

Recently was able to get my car "running" after months of sitting. I siphoned old fuel (1/2 tank) from august of last year from the tank and put about an 1/8th tank of new fuel in (CA91). Unfortunately, I guess my temporary cowl did not prevent water from getting into the 6th cylinder spark well when washing it, so I started it and shut it off after about 5 seconds because it was obviously misfiring in every cylinder due to cylinder 6 not getting any spark. After soaking and vacuuming out the puddle in the 6th cylinder and putting new plugs in (the old ones were destroyed from old fuel my mechanic was running it with). I reset the adaptations, cleared the codes and started up the car again and did not get any misfire codes, and RPM tried to stabilize at around 800rpm but the car was shaking like crazy. I've seen rough idles but my a$$ was literally jumping in the seat, I shut it off for a few minutes then started it up to get a ~10 second idle log to help diagnose the issue. I am decently clueless to reading log values as I have to spend most of my time studying for compsci school, but I noticed I did not get any LTFT/STFT values, not sure if this is normal. I have not cleaned the vanos solenoids yet and the car has brand new motor mounts. I think my mechanic over-torqued the bolts on my aluminum valve cover, so I will retorque those but I don't think it was running long enough for an oil leak to drip into the spark channel. If the logs don't indicate anything major, I can take a video of the idle for support.

Logs: https://datazap.me/u/seaneezy/shaking-idle?log=0&data=12-13-16-20

Thanks!

 

[rac]

repaired the wiring after waiting a month for the terminals to arrive (dealer had none). Started it back up for another open loop. LTFT is also at zero, and the car was working properly before me draining the old fuel from the tank. I noticed the smaller fuel hose on the pump had a ton of play that I never noticed before, could it be the LPFP? I can replace the injectors but the car was actually running with old fuel before doing anything with the injectors, so it would just be weird for them to just die out suddenly. Also de-flashed the car to stock to see if it would help, the idle seemed a lot better but still sputtered after ~15 seconds.

New logs: https://datazap.me/u/seaneezy/815-open-loop

those afr's are all fked up super lean. are you catless? if so and the exhaust doesnt smell super rich, that and the fact you have no STFT still suggests you are not getting enough fuel into several cylinders.

as an aside, i thought the oem hpfp target at idle was a lot less than that what you are running. is your idle hpfp pressure target ~2400psi?

if you want to do more diagnostics before spending money on injectors you could swap front and back banks of injectors and (recode but probably wont effect the answer for this purpose) and relog. you should obviously get an inverse of the AFR readings then (if its physically the injectors) since on bank is a lot leaner than the other.

you can also check the resistance and capacitance of each injector. they will be all very similar. i dont have my notes on me but will post back later with what they should be from my experience with good and bad injectors.

if you get the exact same AFR response after bank swapping (the ultra lean bank swaps) you probably have an electrical issue, wiring harness or dme to injectors. there are a few things to try at that point to narrow it down but that's after you confirm each injector has the same resistance and capacitance.

 

[rac]

i dont have my notes on me but will post back later with what they should be from my experience with good and bad injectors.

my good injectors both old index and latest have all been ~199-200kohm. failed injectors i've measured at numbers a lot higher than that, or infinite.
my good injectors of the same index and age had capacitance that were all similar, 2.30 - 2.40 microfarads - the failed ones in that set were 2.16 and 2.25 microfarads. in my latest index 12 injectors they are all between 2.68 - 2.84 microfarads.

resistance seems to be an easier tell tale as the good injectors have always been in a really tight range compared the bad, but you can check both with a decent multimeter and just look for outliers.

 

[Seaneezy]

my good injectors both old index and latest have all been ~199-200kohm. failed injectors i've measured at numbers a lot higher than that, or infinite.
my good injectors of the same index and age had capacitance that were all similar, 2.30 - 2.40 microfarads - the failed ones in that set were 2.16 and 2.25 microfarads. in my latest index 12 injectors they are all between 2.68 - 2.84 microfarads.

resistance seems to be an easier tell tale as the good injectors have always been in a really tight range compared the bad, but you can check both with a decent multimeter and just look for outliers.

WOW, awesome info. Thanks a lot! I'll try this tomorrow before i buy any injectors.

Regarding the HPFP, I don't really know why the rail pressure would be so high, its a stock HPFP thats probably on its way out too.

 

[ajm8127]

Replacing injectors seems to have solved my misfires during cold starts. I just decided to replace them all and not try my luck with used ones from ebay because I wanted to get this thing fixed and inspected.

datazap.me | ajm8127 | Cold Start

datazap.me

Below are the readings from my old injectors

Cylinder	Index	Capacitance	Resistance
1	10	2.45 uF	infinite
2	10	2.46 uF	infinite
3	09	3.36 uF	200 kohms
4	09	2.43 uF	megaohm range, slowly rising
5	09	2.47 uF	megaohm range, slowly rising
6	09	3.26 uF	260 kohms

I measured with the black meter lead on the injector terminal with the key inside the connector housing. I think this is the terminal with the white wire. It is the terminal on the intake side of the injector (top when viewed with injector installed in the engine).

It is interesting that the two injectors that measured about 3.3 uF have resistances of around 200 kohms. I replaced all injectors two days ago and I did not get readings from the new index 12 ones.

 

[rac]

That's an interesting batch... same experience here with the Mohm and rising or infinite resistance injectors also having the lowest capacitance of the set. In my case it was the injectors with Mohm and rising or infinite resistance that failed to fire or fired weakly. I was testing each injector individually usings output testing available on syvecs.

If anyone starts playing around with them after reading this thread, never disconnect injectors with the car running.

 

[Seaneezy]

Cyl 5 and 6 injectors ran to infinite resistance, so I decided just to bite the bullet and replace all 6 injectors. Coded them properly through INPA and also replaced the #6 coil with one from my old set as it was running infinite resistance compared to the 5 other ones. Started it up to a MUCH better idle, started @ 1100 rpm ish, climbed to 1500 before I shut it off to be 100% sure that everything was fine. STFT is finally logging, but can anyone just double check the fuel trim levels to see if she is running fine? I am probably going to run her for a couple minutes to let adaptations run through, but I need more gas as it's registering <10 miles of range
Theres probably a way to implement the graph directly into the post but I am just going to attach the link here:

Log-08-29-2020-23-13-04

Uploaded by API.

bmw.spoolstreet.com

 

[Seaneezy]

Heres a much better log from this morning. Let it ride to the 600rpm warm point where it started shaking (a lot more mild than before) where the STFT values started going < 0. What does this indicate? MAF falls to ~6 as well. https://bmw.spoolstreet.com/graphs/log-08-30-2020-18-18-01.2719 . Any input is appreciated.

 

[ajm8127]

It seems reasonable to me. Here is my log from after I changed injectors. I didn't log trims or MAF.

datazap.me | ajm8127 | Cold Start

datazap.me

Maybe you just need to drive it a bit and get some more new fuel in the tank. See how it idles once the fluids are up to temp.

 

[Seaneezy]

It seems reasonable to me. Here is my log from after I changed injectors. I didn't log trims or MAF.

datazap.me | ajm8127 | Cold Start

datazap.me

Maybe you just need to drive it a bit and get some more new fuel in the tank. See how it idles once the fluids are up to temp.

somehow, I just noticed there is an actual AFR value logged, that makes diagnosis way easier. Looks good from my end then, I think I am just paranoid about trim levels, gonna put the rest of the car together so I can legally drive it for a little bit (cops already complain about my registered, insured car sitting in my driveway all year)

 

[Seaneezy]

Final closing update: rough lean idle was indeed caused by bad bank 2 injectors diagnosed through resistance values posted above. Car runs better now, however now dealing with codes 2CAB, 2CA7 from what I'm assuming is a bad pre-cat bank 2 O2 sensor that I remember dropping while under the car, causing my bank 2 to run a little leaner than usual but that is not related to the issue stated in this thread. Thanks everyone for amazing support!

 

[martymil]

Most idle, misfire issues are caused by bad injectors, I had a new one fail within the first 500km.

These injectors fail all the time or partially make the car run bad and which is a bastard to find.

 

[Seaneezy]

Most idle, misfire issues are caused by bad injectors, I had a new one fail within the first 500km.

These injectors fail all the time or partially make the car run bad and which is a bastard to find.

wish I learned this when I first bought this car, I was always assuming my misfires had to deal with plugs cracking extremely early without really thinking of what was making the plugs crack early in the first place. Since I bought the car with index 12's already installed, I thought that after the 12th revision of these injectors that the problem would essentially be solved.

Hell, my mechanically-inclined mind believed the cause of my misfires was from excessive PCV in the (cracked) valve cover, so I bought the M18 VC with a nice radium dual-catch can and tapped PCV ports to "completely eradicate" the issue, when it has already caused me more issues than I bought it to fix. The more problems I find with this car, the more I believe in the law of Occam's razor, and I am slowly working to bring the car to mostly OEM tuning philosophies.