N54Tech.com - International Turbo Racing Discussion
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e85johnson e85johnson is offline
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Car: 07 335i FBO
Default Log Review, Stop-Go-Stop-Go-Stop-Go Help Needed - 07-08-2019, 05:44 PM

Hello All,

Long post, logs attached.

Long time reader of this forum, first time posting.
Normally I'm able to find the issue and fix by searching, but I haven't been able to find my exact issue. Maybe the experts here can help.

I was chasing a stutter under 3k WOT, now that's turned into a go, stop, go, stop, go during WOT or light boost, it's really bad if I do a high gear low RPM pull, the car does the go stop thing all the way in the RPM range.

Oddly enough, the car is super smooth if I stay out of boost, smooth all the way up the RPM range.

The go stop thing happened right after changing some parts chasing the stutter problem, maybe it just happened that something like the HPFP or something else just happened to go at the time of the new parts.

Anyway,
I replaced the plugs, coils, boost solenoids and both VANOS. Also cleaned both the map sensors along with replacing the o-rings for those.

When I went for a test drive with the new parts, the stutter was gone, but now the car did the go stop thing.

Me thinking maybe I got a bad part or parts, started to put the old parts back on, starting with the old coils = go stop, old plugs = go stop, old boost solenoids = go stop, old VANOS = go stop.

So now with all the old stuff back on the car, same issue of the go stop, but oddly the stutter issue was gone or turned into the go stop issue.

So I installed all the new parts back on, same issue.

Thinking it was the JB4's menu 10,11 and 12 or the JB4 it's self was going out, I took it out and installed MHD, same issues...

I've bypassed the VAC canisters to rule them out.
I've done the VAC leak test, and verified that the wastegates are fully closed at around 5.9 on the mightyVac.

I've done a smoke test and leak test.

I've tried running the gas tank down and filling up with 93 from Chevron, also ran 3 bottles of techron injector cleaner over 3 weeks of fillups, hoping it might be build up on the injectors, also ran the car for 20 mins on the highway at above 4k rpms in hopes of burning off any build up, I've read this helped with stutter issues, this didn't help.

I've let the car sit overnight and pulled plugs to check for a leaky injector, plugs all dry.

I've been really busy with work and other things going on, and losing time to track this issue down.

Car doesn't have a long crank at all, starts right up.

Around 8 months ago, I've done a ton to the car, and it was running great until now.
List of things done/replaced:
HP fuel sensor & LP fuel sensor.
Vargas stage 1 turbos.
Inlets & outlets.
All gaskets on the car I replaced, oil pan, valve cover, rear main, etc.
Walnut blast.
New clutch & single mass.
Vrsf charge pipe & 3.5 Tmap.
Oil CC.
All 4 O2 sensors.
CXracing intercooler.
Fuel stage 1 pump.
I'm sure I'm missing more that I've done.

I've owned the car since 65k miles, it's been a great daily driver, now at 135k.

I'm guessing it's either the HPFP, injectors, low-pressure pump or maybe the fuel pump control unit. I'm ready to buy all the above at once and just replace it all in one go, but I've read some horror stories of others replacing everything with no change.

One other thing to note, the ECU MOSFETs popped a few months ago, was repaired with replacing all the MOSFETs with new ones. Car was running great for months until the stutter issue started.

Anyway, long post, hopefully the pros can spot the issue in my logs, these are done using MHD, one log is high gear low RPM pull, 2 WOT pulls 2nd to 3rd and one log with a start up of car from off.

I've been running the car very very hard to get something to break or at least give me a code to work off, no codes at all...

I've reset all adaptation and drove 500 miles, didn't fix it.

In the logs, you can see the HP, LP and boost all go up and down during the go stop going issue.

Thanks for any help, beers to all that help
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e85johnson e85johnson is offline
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Car: 07 335i FBO
Default 07-08-2019, 07:46 PM

I noticed in my WOT logs, the Accel ped POS % is at 99.6, but the throttle position goes up and down?? What would could be making this happen? All these logs are with traction control fully disabled.
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e85johnson e85johnson is offline
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Car: 07 335i FBO
Default 07-13-2019, 10:43 AM

I fixed my issues!!

Turns out my stutter issue that started this crazy adventure in troubleshooting that my brand new boost solenoids are bad, or at least not playing nice with the dme. Even tho I did the normal vac test with these solenoids and they read correct levels running at idle and in the car while driving.

I ended up retesting the OLD solenoids off the car, mightVac to the vac side of the solenoid, and I found that one of them would not hold vac unless I had plugged the out on the solenoid . This would explain why it tested fine on the car, because the out is connected to the wastegates.

Put the tested good OLD solenoid on the car with 2 T's, so the one solenoid is running both wastegates.

Went for a drive, car drives like new, no stutter, no throttle closing, no surging at all, boost holds at 18+ lbs on MHD 2.5+ map .

Not really sure why the new solenoids had these issues, they both tested good but they sure didn't play nice with the dme.

Thanks to dpaul on e90post.com for help with looking at my logs, he helped to point out it had to be a boost control type of issue and it sure was.
The way the car was acting, it could of been blamed on a lot of big ticket items to buy.

O well, time to return the new boost solenoids and buy 2 more from someplace else this time.
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Terry @ BMS Terry @ BMS is offline
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Default 07-13-2019, 11:16 AM

Glad it's sorted! Will leave the thread here for posterity.


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