Technical Intermittent Misfire/Jerk cruising in highway & Stalling at stoplights

Pulstura

New Member
Aug 2, 2022
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Hey guys,
I'm getting this intermittent issue with my 335i where it misfires/jerks while cruising and occasionally stalls at stop lights.
These issues seem to appear only when the cars warm. The car doesn't throw any codes and mechanics can't seem to replicate this issue.
I've managed to data log through MHD and captured 3 occasions when it jerked/misfired and it looks to have a similar pattern on the charts.
Any idea what could be causing this?

Updated MHD datalog. Weird dip in rpm from 2.5k to 1.2k in a split second
 

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MR-KRAKA

Specialist
May 23, 2020
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You might have better luck posting the actual log specifically in the user friendly embedded version. Need to be able to see all the possible factors involved.
 

ansch

Lurker
Sep 23, 2018
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E82 135i SGM
Crank angle sensor? Symptom sounds similar but I did get code specific to the crank angle sensor when mine was dying.
 

bakerdou

Private
May 13, 2021
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Mine used to tremble heavily at the traffic lights after a spirited drive.
After I swapped the coil to B58 ones and pull the gap from .020 to .024 the problem disappeared. I also did changed my pcv valve.
 

bakerdou

Private
May 13, 2021
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I've attached a new MHD datalog which I captured today.

I've pulled my Vanos solenoids, cleaned them and put them back in the other way round.
I still got misfire in the highway, you can also see the RPM drop from 2.5k to 1.2k for a split second which is really odd.
The AFR ran into extremely lean area before some detonation came around and choked it to 1200rpm. Also all cylinder tries to calm the detonation by trying to retard the timing to their maximum, you dont see -5 degree with 2500rpm cruise much, at least not that long duration. It looks totally not fine to me, possibly some issues with fueling system.
I would start with hpfp as your rail pressure dropped from 2400psi to 700(that's insanely low), and causing your afr to increase from 14 to 17 in a very fixed pattern( check your rail pressure figure).
 

Pulstura

New Member
Aug 2, 2022
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The AFR ran into extremely lean area before some detonation came around and choked it to 1200rpm. Also all cylinder tries to calm the detonation by trying to retard the timing to their maximum, you dont see -5 degree with 2500rpm cruise much, at least not that long duration. It looks totally not fine to me, possibly some issues with fueling system.
I would start with hpfp as your rail pressure dropped from 2400psi to 700(that's insanely low), and causing your afr to increase from 14 to 17 in a very fixed pattern( check your rail pressure figure).
Thanks for checking this out. The highway cruising is with 8-9% throttle.
I assumed 700psi was the normal range for the fuel rail and the spike to 2400psi was the odd reading not the inverse?
I was never doing WOT in this graph
 

bakerdou

Private
May 13, 2021
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Thanks for checking this out. The highway cruising is with 8-9% throttle.
I assumed 700psi was the normal range for the fuel rail and the spike to 2400psi was the odd reading not the inverse?
I was never doing WOT in this graph
Oh sure, I should have addressed this the other way. You should see constant 800ish rail pressure cruising. The spike indicates there are either clogged injectors or hpfp pistons, so it needed to build up enough pressure to push through, which resulted in the irregular rail pressure spikes.
 

Pulstura

New Member
Aug 2, 2022
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Oh sure, I should have addressed this the other way. You should see constant 800ish rail pressure cruising. The spike indicates there are either clogged injectors or hpfp pistons, so it needed to build up enough pressure to push through, which resulted in the irregular rail pressure spikes.
I agree with you about the car going lean. I read somewhere that the O2 sensors could give false lean reading if it gets wet from fuel.

I'm not sure when the plugs and coils were replaced as the previous owner had the car from 70,000 km to 140,000 km and I'm pretty sure they haven't been replaced during his ownership. My assumption is if the car is misfiring due to coil/plugs, it could cause the O2 sensor to read false lean readings causing all this timing to be pulled.

Still doesn't explain the spike in rail fuel pressure, perhaps the DME trying to cut power and fuel not being used up because it thinks its going to lean? Or as you explained clogged up injectors etc.

I'll report back once the coil/plugs arrive and see what I get
 

fmorelli

Lieutenant General
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Aug 11, 2017
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With issues like this, providing a full background on your car would be helpful. Mileage, maintenance (including work in last many months), upgrades. Work done prior to the issue surfacing, and so on.

Without anything else, I'm thinking there may be a ground issue.
 

carabuser

Lieutenant
Oct 2, 2019
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Looks like car jumps into emergency mode which would explain the VANOS change, fuel pressure jump and timing drop.

Try logging the fuel mode parameter
 

Pulstura

New Member
Aug 2, 2022
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I'm still running into the jerk/jolt/misfire whatever it is.

New logs been provided after the maintenance items I've listed below has been done.

Replaced all spark plugs with oem bosch and coils with new eldor coils. - No obvious signs, doesn't smell of fuel.
Replaced the old PCV valve with an aftermarket RB PCV valve.
Reset adaptations, after performing the above maintenance.
Injector Indexes - Cylinder 1 = Index 9, Remaining Cylinders = Index 7

Observations:
- Timing Drops First, followed by VANOS Intake/Exhaust drop
- RPM and the initial timing drops at the same time, RPM dips from 2500 to 1250 in a split second

Questions:
- What can causes timing to drop? This log only shows timing for cylinder 1 and 4 timing, but from previous logs all cylinders timing look to drop together. "NOTE: There's no timing correction occurring at the same time"
- RPM dips, could this be sensor related? Strange this only occurs once the car is warm and running in optimal temperature.
- Noob question - What does *crk stand for in these logs? I couldn't find any info on this...

With issues like this, providing a full background on your car would be helpful. Mileage, maintenance (including work in last many months), upgrades. Work done prior to the issue surfacing, and so on.

Without anything else, I'm thinking there may be a ground issue.
I've only owned the car for 2 months, last service looks to have been done by BMW on November last year.
The car has done 144,000 km = ~89,500 miles, and no upgrades fully stock when the issue started.
Looks like car jumps into emergency mode which would explain the VANOS change, fuel pressure jump and timing drop.

Try logging the fuel mode parameter
Fuel mode's been added into the log, no change when the jerk/jolt occurs.
 

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bakerdou

Private
May 13, 2021
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Hard to precisely locate the mechanism caused the rpm dip.
I would argue the injectors need replacement, even the hpfp if it's not been replaced. Few n54s using early day injectors can run without issues.
 

carabuser

Lieutenant
Oct 2, 2019
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Really strange that no error code comes up. It does look like the crank sensor is having a hiccup.

In your situation I'd buy a crank sensor and replace it. While in there check all the wiring for damage and verify the ground strap around the driver side mount is OK.
The budget option would be to get a used crank sensor from a breaker.

You've exhausted all sensible diagnostic steps short of getting an oscilloscope and in that last log it looks pretty certain to be a false RPM reading.
 

Pulstura

New Member
Aug 2, 2022
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3
0
Hey all! I know it's been awhile since I last commented here. I've managed to fix the jerking which the car made.

From reading the data more closely, it looked like ignition cut and fuel cut was occurring due to the quick rise in rail pressure and ignition timing dropping on all 6 cylinders. -> I read somewhere, if the crank sensor sends faulty signals the DME will cut ignition/fuel.

I replaced both cam sensors and crank sensor and it looks like it fixed the problem! Hope this helps anyone else with diagnostics :)