[jyeah]

Hi All,

I have been experiencing an extremely weird oscillation while cruising and keeping my throttle steady for a while now. The feeling is as if the car is oscillating with a very slight stalling feeling followed by a slight pulling feeling. The moment I let my throttle off or press on it further, the oscillation goes away. The rpm needle also fluctuates. I tried doing some logs and it seems like my HPFP is very unstable, fluctuating up and down, while the requested stays constant. My LPFP is very stable as well.

Has anyone experienced anything like this? I have Cobb V3 installed with the newest firmware and it is pro-tuned. I also have tried clearing the codes, resetting the adaptations, and flashing back to stock. None of these helped.

A while ago, I recall that the oscillation went away for a short while when I added a bottle of techron after a fuel up, but came back after that. I don't know if this was a placebo effect and I haven't tried it again.

Here's a link to my logs.

http://1drv.ms/1qxfvJT

Any help would be much appreciated!

[jyeah]

Also, I tried using datazap to take a quick look. The thing I do notice is that there's usually a change in cylinder timing from 30->15 followed by a dip in HPFP pressure.

[badass335]

I was just going to post the same issue. I have Cobb V3 and am going through the ptf tune as well. I've had way too many revisions and still have this issue. It seems like the car is taking off, and then a parachute opens slowing me down and then the parachute rips and i take off again.

I had OFT with Procede stacked and the car ripped through the gears. I am running a FBO car with Meth. I had Procede control my aquamist meth and was running IA8OS ecu.

I then had an ecu failure (mosfet issue) so bmw replaced it with IJE0S now. Also got 6 new coils and injectors and plugs. As such, i removed Procede/OFT and got Cobb v3. Connected Aquamist directly to ECU.

I am trying to troubleshoot as not to blame tunes. I replaced the Boost Solenoids with all boost hoses and then i read somewhere that vanos solenoids could also cause this so replaced that as well. Running out of ideas.

I should also mention as OP stated, i can be driving with throttle constant and the car is surging or fluctuating though the pedal is held constant.

[cstmx_ryder]

Originally Posted by jyeah

Hi All,

I have been experiencing an extremely weird oscillation while cruising and keeping my throttle steady for a while now. The feeling is as if the car is oscillating with a very slight stalling feeling followed by a slight pulling feeling. The moment I let my throttle off or press on it further, the oscillation goes away. The rpm needle also fluctuates. I tried doing some logs and it seems like my HPFP is very unstable, fluctuating up and down, while the requested stays constant. My LPFP is very stable as well.

Has anyone experienced anything like this? I have Cobb V3 installed with the newest firmware and it is pro-tuned. I also have tried clearing the codes, resetting the adaptations, and flashing back to stock. None of these helped.

A while ago, I recall that the oscillation went away for a short while when I added a bottle of techron after a fuel up, but came back after that. I don't know if this was a placebo effect and I haven't tried it again.

Here's a link to my logs.

http://1drv.ms/1qxfvJT

Any help would be much appreciated!

If your HPFP is unstable, could it be that it's failing? I mean, what other causes could it be?

[DuDai]

For me i had this for the longest time. What solved it was adjusting WGDC to 2000RPM on the JB4 in menu 12. I know that won't be adjustable on the Cobb though so not much help. But it drove me nuts for the longest time. If i go higher than that on the Jb4 for the setting it will return on me.

[e92_enthusiast_1]

Could DV's cause this symptom. I wanna say sometimes I feel the same way like if the DVs are stuck open. Not sure how to explain it. I'm.upgrading to forges here soon.

[BMW_drei]

I had something similar a while back -- subtle surging when on the highway cruising at constant speed. It went away after cleaning the VANOS solenoids. Maybe unrelated?

[badass335]

Originally Posted by e92_enthusiast_1

Could DV's cause this symptom. I wanna say sometimes I feel the same way like if the DVs are stuck open. Not sure how to explain it. I'm.upgrading to forges here soon.

I have forge dv's. Cleaned and serviced them just to be sure.

[badass335]

Originally Posted by BMW_drei

I had something similar a while back -- subtle surging when on the highway cruising at constant speed. It went away after cleaning the VANOS solenoids. Maybe unrelated?

I put I brand new vanos solenoids.

[2Times]

I had exactly the same thing, almost felt like a giant gust of wind was slowing me down randomly. I had my turbos replaced and recoded 6AT. That was done by BMW (they did the TCU because I did the Alpina flash). It's better now.
I have an '08 e92 6AT.

[jyeah]

Originally Posted by cstmx_ryder

If your HPFP is unstable, could it be that it's failing? I mean, what other causes could it be?

That's what I thought at first, as I saw fuel pump codes, but then it went away. If you take a look at my logs you might see the cylinder timing drop first and then followed by the HPFP dip and oscillation. Maybe there's something else I'm looking at that can tell the full story.

It's really confusing. Also, I have Forge DV's as well and they were serviced not too long ago.

[harms]

Old thread, but did anyone find a solution to this issue?

I have the same problem. Dips in hpfp pressure at part throttle cruising, dme compensates with stft, afr's go rich, then stft goes the opposite way, and so on.

[Derek Keenan]

Originally Posted by harms

Old thread, but did anyone find a solution to this issue?

I have the same problem. Dips in hpfp pressure at part throttle cruising, dme compensates with stft, afr's go rich, then stft goes the opposite way, and so on.

Having the same issue, did you find out what fixed it

[iqraceworks]

I had the same issue about 4 months ago...but I was never able to run a log to see what was going on. I had a bigger LPFP that needed to go in, and I have never had that issue since. Not sure if the new LPFP fixed it......or it was just a coincidence.

I've been seeing several people on different forums having the same light surging issues while cruising around town at a constant throttle and light load. Haven't really seen a definite fix yet....

[Derek Keenan]

Originally Posted by iqraceworks

I had the same issue about 4 months ago...but I was never able to run a log to see what was going on. I had a bigger LPFP that needed to go in, and I have never had that issue since. Not sure if the new LPFP fixed it......or it was just a coincidence.

I've been seeing several people on different forums having the same light surging issues while cruising around town at a constant throttle and light load. Haven't really seen a definite fix yet....

I have a stage 3 bucketless fuel pump and it still does it

[Wolf 335]

Add me to the list as well.

[thormessiah]

Resetting adaptations on MHD worked for me. Only happened on OTS maps

[Derek Keenan]

Originally Posted by thormessiah

Resetting adaptations on MHD worked for me. Only happened on OTS maps

I've tried that many times but doesn't work for me

[Wolf 335]

This issue is not related to any tune or map.

[iqraceworks]

Originally Posted by Wolf 335

This issue is not related to any tune or map.

Don't leave everyone guessing........what's causing this issue then???

[ky0u]

Originally Posted by iqraceworks

Don't leave everyone guessing........what's causing this issue then???

Idk if he's just saying what he eliminated as the possible issue. I had similar behavior pop up a couple weeks ago. Reset adaptations as a first step but issue still occurs. Mine is accompanied by an occasional weird engine start so I'm not sure if it's truly the same issue as OP. When I cold start the car after sitting overnight, it doesn't fully crank, it just turns over almost accidentally. Similar to how active start/stop vehicles fire up when youre about to move from a stop. Absolutely zero codes though, so frustrating


Haven't had time to go out and datalog properly yet, but digging through past threads has been giving me such a wide range of possibilities. Lpfp, o2s, vanos, cats, etc.

[Derek Keenan]

Originally Posted by Wolf 335

This issue is not related to any tune or map.

I emailed a log to my tuner of it doing it and he verified it wasn't a tune issue because he has both of the banks the same and bank 2 acts worse than bank 1