[theoforest]

Hello everyone,
before throwing a bunch of money at parts, i figured ill post here if someone had a similar situation or that can help me figure out whats wrong.

So the issue is at low load, the car will jerk, kinda like an hesitation, only happen at low load, (throttle position between 8% and 12%), car pulls super great at wot and moderate throttle.

I tought my issue would be a leaky injecor (wich i had) but after i changed it and coded it, it still happen.

Im mostly stock except catless dp, and external pcv. Running stage2 mhd (with dp fix and without it still jerk, but wiht the fix, afr are stable at idle)

Tested all injector for leak and there are none.
I do have a leaky valve cover gasket wich ive order but unsure how that would affect low load and not high load.

Coil and plug have been changed about a year ago and vanos solenoid are new of a few weeks. I also changed my throttle body a few days ago to eliminate the possibilities of it being bad.

When it happen, LFPF is about 80+ psi and rail pressure between 580 and 750.

Here are the logs


WOT
https://datazap.me/u/th%C3%A9o/wot-m...og=0&data=3-17

Steady speed with CC
https://datazap.me/u/th%C3%A9o/cruze...og=0&data=3-17

I cant find much info online. Apprently was a known issue before mhd release the dp fix, but that doesnt do the trick for me apparently.

Any input would be greatly appreciated, thanks.

[Jonnyweninger]

Originally Posted by theoforest

Hello everyone,
before throwing a bunch of money at parts, i figured ill post here if someone had a similar situation or that can help me figure out whats wrong.

So the issue is at low load, the car will jerk, kinda like an hesitation, only happen at low load, (throttle position between 8% and 12%), car pulls super great at wot and moderate throttle.

I tought my issue would be a leaky injecor (wich i had) but after i changed it and coded it, it still happen.

Im mostly stock except catless dp, and external pcv. Running stage2 mhd (with dp fix and without it still jerk, but wiht the fix, afr are stable at idle)

Tested all injector for leak and there are none.
I do have a leaky valve cover gasket wich ive order but unsure how that would affect low load and not high load.

Coil and plug have been changed about a year ago and vanos solenoid are new of a few weeks. I also changed my throttle body a few days ago to eliminate the possibilities of it being bad.

When it happen, LFPF is about 80+ psi and rail pressure between 580 and 750.

Here are the logs


WOT
https://datazap.me/u/th%C3%A9o/wot-m...og=0&data=3-17

Steady speed with CC
https://datazap.me/u/th%C3%A9o/cruze...og=0&data=3-17

I cant find much info online. Apprently was a known issue before mhd release the dp fix, but that doesnt do the trick for me apparently.

Any input would be greatly appreciated, thanks.

Mine does the same, can’t seem to figure it out either. I had a code pop up for the low pressure fuel pump sensor. that’s going to be my next project and i’ll see if it fixes it. And do you have a cel on?

[theoforest]

Originally Posted by Jonnyweninger

Mine does the same, can’t seem to figure it out either. I had a code pop up for the low pressure fuel pump sensor. that’s going to be my next project and i’ll see if it fixes it. And do you have a cel on?

Nope no code, engine seems very happy except for that
My post cat o2 sensor are acting up a bit, ill give that a try after the valve cover gasket

[Jonnyweninger]

Originally Posted by theoforest

Nope no code, engine seems very happy except for that
My post cat o2 sensor are acting up a bit, ill give that a try after the valve cover gasket

Strange… my car also seems very very happy to do a wot pull but around 1.5 - 2k rpm’s it seems like something is jerking

[theoforest]

Originally Posted by Jonnyweninger

Strange… my car also seems very very happy to do a wot pull but around 1.5 - 2k rpm’s it seems like something is jerking

I noticed too around this but mine it’s all the rpm band but it depend how much throttle I applied, it happen even at 4K rpm if low throttle, it’s less intense but I can still feel it.
I’m probably overdue for walnut blast but I would expect to show issues more in higher load..

[Jonnyweninger]

Originally Posted by theoforest

I noticed too around this but mine it’s all the rpm band but it depend how much throttle I applied, it happen even at 4K rpm if low throttle, it’s less intense but I can still feel it.
I’m probably overdue for walnut blast but I would expect to show issues more in higher load..

There is also that yes. Could be a bunch of gunk in there

[theoforest]

Originally Posted by Jonnyweninger

There is also that yes. Could be a bunch of gunk in there

I got a upgraded Charge pipe coming with my valve cover gasket, I’ll take a look at my intake at the same time, depends how it look I might do a walnut blast

[bigsurge]

I have the same issue and made a thread about it aswell, if you log and look at your afrs do they seem to spike from 14 to 19 ?

I have yet to start troubleshooting mine

[theoforest]

Originally Posted by bigsurge

I have the same issue and made a thread about it aswell, if you log and look at your afrs do they seem to spike from 14 to 19 ?

I have yet to start troubleshooting mine

Mine are going from 13 to 17 while cruising

Throttle body also oscillate

I changed a bunch of parts recently and reset my adaptation with INPA(I tried before with MHD and it didn’t fixed it) , i havent had the issue reappear yet but I’ll wait a few days / weeks to adapt properly and then I’ll know for sure.

[lowrydr310]

Originally Posted by Jonnyweninger

Mine does the same, can’t seem to figure it out either. I had a code pop up for the low pressure fuel pump sensor. that’s going to be my next project and i’ll see if it fixes it. And do you have a cel on?

My 335 was jerking under light load, took me a while to figure it out because I didn't have any logging capability. Only a low pressure fuel code. Once I did some data logging I realized my low pressure system fuel pressure never went over 50, and occasionally spiked down into single digits. It was a bad sensor, once I replaced that all the jerking went away.

I looked at the logs above and the low pressure sensor seems fine so that's probably not the OPs issue.

[Jonnyweninger]

Originally Posted by lowrydr310

My 335 was jerking under light load, took me a while to figure it out because I didn't have any logging capability. Only a low pressure fuel code. Once I did some data logging I realized my low pressure system fuel pressure never went over 50, and occasionally spiked down into single digits. It was a bad sensor, once I replaced that all the jerking went away.

I looked at the logs above and the low pressure sensor seems fine so that's probably not the OPs issue.

yes i actually do have the code for that low pressure fuel sensor. and i also have the part just haven’t had time to do it yet

[NMSUman]

Originally Posted by theoforest

Hello everyone,
before throwing a bunch of money at parts, i figured ill post here if someone had a similar situation or that can help me figure out whats wrong.

So the issue is at low load, the car will jerk, kinda like an hesitation, only happen at low load, (throttle position between 8% and 12%), car pulls super great at wot and moderate throttle.

I tought my issue would be a leaky injecor (wich i had) but after i changed it and coded it, it still happen.

Im mostly stock except catless dp, and external pcv. Running stage2 mhd (with dp fix and without it still jerk, but wiht the fix, afr are stable at idle)

Tested all injector for leak and there are none.
I do have a leaky valve cover gasket wich ive order but unsure how that would affect low load and not high load.

Coil and plug have been changed about a year ago and vanos solenoid are new of a few weeks. I also changed my throttle body a few days ago to eliminate the possibilities of it being bad.

When it happen, LFPF is about 80+ psi and rail pressure between 580 and 750.

Here are the logs


WOT
https://datazap.me/u/th%C3%A9o/wot-m...og=0&data=3-17

Steady speed with CC
https://datazap.me/u/th%C3%A9o/cruze...og=0&data=3-17

I cant find much info online. Apprently was a known issue before mhd release the dp fix, but that doesnt do the trick for me apparently.

Any input would be greatly appreciated, thanks.

My only contribution is if it is doing it at about ~1550 RPM, you could be having a VANOS solenoid begin to fail. I just went through this in the new year with my 07.

The symptom you describe is similar to what I had as a result of a faulty replacement part, but my only (low probability) thought is that if the VANOS solenoid was stuck in a position, you may have the same surging sound.

I say this because when I did the swap, it 'felt' like a Transmission error was occurring after the swap when in reality the faulty part was preventing the VANOS system to operate as in intended on the exhaust Camshaft.

You can see two videos in my thread to see if you have a similar issue.

If you do go down the path, I would suggest steering clear of the URO brand solenoids, just based on my experience.

https://www.e90post.com/forums/showthread.php?t=2069234

[theoforest]

Originally Posted by NMSUman

My only contribution is if it is doing it at about ~1550 RPM, you could be having a VANOS solenoid begin to fail. I just went through this in the new year with my 07.

The symptom you describe is similar to what I had as a result of a faulty replacement part, but my only (low probability) thought is that if the VANOS solenoid was stuck in a position, you may have the same surging sound.

I say this because when I did the swap, it 'felt' like a Transmission error was occurring after the swap when in reality the faulty part was preventing the VANOS system to operate as in intended on the exhaust Camshaft.

You can see two videos in my thread to see if you have a similar issue.

If you do go down the path, I would suggest steering clear of the URO brand solenoids, just based on my experience.

https://www.e90post.com/forums/showthread.php?t=2069234

I haven’t updated the post yet cause I feel like it’s been not long enough

But I changed Vanos(not sure the brand but could be uro..) and it didn’t change anything

But I did reset all adaptations using inpa and it hasn’t done it again yet both in first gear and cruising, I had reset adaption with mhd before so it’s a bit weird. It’s been about a week now, I’ll see if it come back and update the OP if not