[Dave92N54]

I'm curious, have any of you had this fail or go bad? I had an issue with surging on low throttle, and it pretty much disappeared however on Saturday I did quite a bit of enthusiastic driving (nothing crazy) and didn't drive the car yesterday.

Here we are today, I start the car this morning and the idle seemed a little lumpy (tach was steady, but the ol' butt could tell).

Started it again about an hour ago, and it was lumpy again, went for a drive and the car drove fine, however towards the end I started to get some serious low throttle surging. I took a log of it happening as well as a WOT and idle log if anyone wishes to look, however nothing seems all that out of the ordinary other than in the log I took of it happening you can see the AFR and STFTs start oscillating (obviously when surging), this is why I suspect an exhaust leak at the gasket.

I doubt it's a boost leak of any kind, seems to make boost fine. WOT log shows initial spool right to target, and then i'm off by about 1psi for a few seconds until it rides target again until redline.

[mweisdorfer]

Originally Posted by Dave92N54

I'm curious, have any of you had this fail or go bad? I had an issue with surging on low throttle, and it pretty much disappeared however on Saturday I did quite a bit of enthusiastic driving (nothing crazy) and didn't drive the car yesterday. Here we are today, I start the car this morning and the idle seemed a little lumpy (tach was steady, but the ol' butt could tell). Started it again about an hour ago, and it was lumpy again, went for a drive and the car drove fine, however towards the end I started to get some serious low throttle surging. I took a log of it happening as well as a WOT and idle log if anyone wishes to look, however nothing seems all that out of the ordinary other than in the log I took of it happening you can see the AFR and STFTs start oscillating (obviously when surging), this is why I suspect an exhaust leak at the gasket. I doubt it's a boost leak of any kind, seems to make boost fine. WOT log shows initial spool right to target, and then i'm off by about 1psi for a few seconds until it rides target again until redline.

Codes?

[Dave92N54]

Originally Posted by mweisdorfer

Codes?

None. In fact, this may sound crazy but my car has never thrown a CEL. I have the typical downpipe shadow codes, and I made sure to check codes immediately after the surging, still nothing.

There is also quite an extensive maintenance list, i've done almost anything you can think of. If it matters, primary and secondary 02s literally have less than 1k on them. I'm sure i'll get all the typical "check over your work" responses but I can assure you the install went fine, and I gave the car a good womping after install to be sure. No 02 codes (other than the shadow codes) and no issues until today.

It seems to happen when manifold vacuum is pretty high, around -10.6-11psi. I've considered PCV but the low side valve is fairly new, i'd like to move to a catch can though so, an excuse to upgrade wouldn't be too bad

[Dave92N54]

Well, flashed the car back to stock, reset all adaptations, flashed stage 1+ V9 again and started it up, let it idle about 3 minutes and took it for a drive until it was warmed up.

Surging continued to happen while driving at low RPM until warmed up, and continued when warmed up. I then took another WOT log, and this time I never even touched boost target. I was down about 2psi for most of the pull, so i'll investigate a boost leak tomorrow. What I find odd is that despite being down on boost, WGDC did not go up in an attempt to meet target.

This also reminds me that on startup after the reset and reflash, there was significantly less WG rattle than before, not sure why but it was absolutely less.

[Dave92N54]

Here is a log of it happening:

https://datazap.me/u/e92dave/low-thr...&data=3-22

The thing that is so odd to me is this has zero correlation to RPM, it does not affect it at all, yet you can feel it quite a bit. It just seems that one bank leans out, trims bring it back, the other bank leans out, trims bring it back and then this just keeps happening. It doesn't seem to be directly correlated to vacuum since it doesn't always do it when under high vacuum, but when it does do it, it's under high vacuum. I'm pretty stumped here, especially if I don't come up with some kind of a boost leak in the morning. I've read just about every thread across every forum I can find on this topic and nothing seems to be what i'm experiencing.

I've wondered if it may be my evap valve (the one plugged into the throttle body), mine seems to tick much louder than most, i've even had a few coworkers ask if my car is alright because of how loud it can be. Never throws a CEL though...

[Bimmer_Bro]

Originally Posted by Dave92N54

Well, flashed the car back to stock, reset all adaptations, flashed stage 1+ V9 again and started it up, let it idle about 3 minutes and took it for a drive until it was warmed up.

Surging continued to happen while driving at low RPM until warmed up, and continued when warmed up. I then took another WOT log, and this time I never even touched boost target. I was down about 2psi for most of the pull, so i'll investigate a boost leak tomorrow. What I find odd is that despite being down on boost, WGDC did not go up in an attempt to meet target.

This also reminds me that on startup after the reset and reflash, there was significantly less WG rattle than before, not sure why but it was absolutely less.

Have you done boost solenoids?
Also check those stupid vacuum canisters for leaks.
A bad boost solenoids can cause weird and inconsistent boost issues.

[Dave92N54]

Originally Posted by Bimmer_Bro

Have you done boost solenoids?
Also check those stupid vacuum canisters for leaks.

I have not tested the solenoids themselves, and canisters are good. I recently dealt with an issue where I was losing vacuum immediately after shutoff, turned out to be a leaky vacuum pipe that connects to the vacuum pump, so there were checked when looking for that issue. I'd wish it were something as simple as the solenoids but both appear to be working fine. I could probably find time this weekend to pull them and test though.

[Bimmer_Bro]

Originally Posted by Dave92N54

I have not tested the solenoids themselves, and canisters are good. I recently dealt with an issue where I was losing vacuum immediately after shutoff, turned out to be a leaky vacuum pipe that connects to the vacuum pump, so there were checked when looking for that issue. I'd wish it were something as simple as the solenoids but both appear to be working fine. I could probably find time this weekend to pull them and test though.

I'm not sure if there is an actual way to test if they are good or bad. They aren't too expensive. Most owners just replace if they suspect they could be the problem. They can cause some really goofy inconsistent issues.

[Dave92N54]

Originally Posted by Bimmer_Bro

I'm not sure if there is an actual way to test if they are good or bad. They aren't too expensive. Most owners just replace if they suspect they could be the problem. They can cause some really goofy inconsistent issues.

I get paid this friday, I have the money now but i've been saving for a full M Sport conversion I guess I'll order a set. I did just run out there and pull the line off a canister, I heard the vacuum. Interestingly though, it sounded almost like it was bleeding off from under the engine cover. I heard and felt the suction at the canister but if I took my finger off the canister, it really sounded like it was bleeding off under there. I have some leftover line laying around so I could throw some new lines to the bottom of the canisters for giggles in the morning. I'll keep this updated if it does or does not help.

[Bimmer_Bro]

Originally Posted by Dave92N54

I get paid this friday, I have the money now but i've been saving for a full M Sport conversion I guess I'll order a set. I did just run out there and pull the line off a canister, I heard the vacuum. Interestingly though, it sounded almost like it was bleeding off from under the engine cover. I heard and felt the suction at the canister but if I took my finger off the canister, it really sounded like it was bleeding off under there. I have some leftover line laying around so I could throw some new lines to the bottom of the canisters for giggles in the morning. I'll keep this updated if it does or does not help.

Interesting! Have you done all your vacuum lines? The hard lines under the cover can crack but you shouldn't have a leak if you heard the pressure release once you disconnected.
Solenoids is just a guess. They don't last forever and most people with over 100k miles have replaced them.
I think the only way I have seen exhaust leaks between the turbo and the downpipes is if the v band clamps break or the bolt backs out. The turbo gasket is breaded metal and is pretty durable. Good luck!

[Dave92N54]

Originally Posted by Bimmer_Bro

Interesting! Have you done all your vacuum lines? The hard lines under the cover can crack but you shouldn't have a leak if you heard the pressure release once you disconnected.
Solenoids is just a guess. They don't last forever and most people with over 100k miles have replaced them.
I think the only way I have seen exhaust leaks between the turbo and the downpipes is if the v band clamps break or the bolt backs out. The turbo gasket is breaded metal and is pretty durable. Good luck!

I have done all the lines, however I found some kind of 'warped' due to heat, shitty lines I guess. I replaced those ones with better line but I wouldn't be too surprised if the lines that go from the hard lines on top of the valve cover to the bottom of the canisters were warped as well. Been a little side tracked this morning, registering for summer classes and other things.

How many times did I just say 'line' or 'lines'

[BSM n54iS]

Originally Posted by Dave92N54

I have done all the lines, however I found some kind of 'warped' due to heat, shitty lines I guess. I replaced those ones with better line but I wouldn't be too surprised if the lines that go from the hard lines on top of the valve cover to the bottom of the canisters were warped as well. Been a little side tracked this morning, registering for summer classes and other things.

How many times did I just say 'line' or 'lines'

More important is how many have you done?

[Dave92N54]

Originally Posted by BdSM n54iS

More important is how many have you done?

I'm not sure what you mean? I've done all the vacuum lines...

It's pretty safe to say I have the line routing memorized though, in all honesty I think there's less than a handful of parts on these engines that I'm unfamiliar with at this point, I may have a problem N54 on my mind 24/7 LOL

[BSM n54iS]

Originally Posted by Dave92N54

I'm not sure what you mean? I've done all the vacuum lines...

It's pretty safe to say I have the line routing memorized though, in all honesty I think there's less than a handful of parts on these engines that I'm unfamiliar with at this point, I may have a problem N54 on my mind 24/7 LOL

jp dude. Ya this happens to me about once a year where I get obsessed chasing something down. Find it best to take one part at a time until problem is eliminated

Edit: Drugs are bad.

[mweisdorfer]

Originally Posted by Dave92N54

None. In fact, this may sound crazy but my car has never thrown a CEL. I have the typical downpipe shadow codes, and I made sure to check codes immediately after the surging, still nothing.

There is also quite an extensive maintenance list, i've done almost anything you can think of. If it matters, primary and secondary 02s literally have less than 1k on them. I'm sure i'll get all the typical "check over your work" responses but I can assure you the install went fine, and I gave the car a good womping after install to be sure. No 02 codes (other than the shadow codes) and no issues until today.

It seems to happen when manifold vacuum is pretty high, around -10.6-11psi. I've considered PCV but the low side valve is fairly new, i'd like to move to a catch can though so, an excuse to upgrade wouldn't be too bad

I personally like the BMS gaskets for the mid-pipe to down pipe connection. They seem to make a better seal.

As far as the turbo to downpipe connection, I'd advocate for OEM BMW turbo seals & OEM BMW V-bands. There are far too many posts in here and other forums where people using after mkt v-bands that don't fit correctly. The V-bands can be tricky and sometimes a b@tch to get on correctly. Having OEM bands is the only way to ensure a good seal.

It's always a great idea to put rear down pipe in first and very loosely put on the mid-pipe to downpipe connection first. I mean really loose (3-4 turns of the nut)

[Dave92N54]

Originally Posted by mweisdorfer

I personally like the BMS gaskets for the mid-pipe to down pipe connection. They seem to make a better seal.

As far as the turbo to downpipe connection, I'd advocate for OEM BMW turbo seals & OEM BMW V-bands. There are far too many posts in here and other forums where people using after mkt v-bands that don't fit correctly. The V-bands can be tricky and sometimes a b@tch to get on correctly. Having OEM bands is the only way to ensure a good seal.

It's always a great idea to put rear down pipe in first and very loosely put on the mid-pipe to downpipe connection first. I mean really loose (3-4 turns of the nut)

New OEM V Bands were used when I put my downpipes on 2 months ago

and that is exactly what I did when installing the downpipes

[Dave92N54]

well, did some more digging. The vacuum cap on my manifold nipple has disappeared! This has to be the cause! Time to go buy some nipple caps

Part of it is still there! It literally exploded! Nice job BMS, lol

[BSM n54iS]

Originally Posted by Dave92N54

well, did some more digging. The vacuum cap on my manifold nipple has disappeared! This has to be the cause! Time to go buy some nipple caps

Part of it is still there! It literally exploded! Nice job BMS, lol

You could always get some clamps for them too

[Dave92N54]

Originally Posted by BdSM n54iS

You could always get some clamps for them too

It had a ziptie on it lol