[iCstyle]

Hi guys

I'm fighting with a problem since some weeks/months on my car:
When I'm crusing or off throttle, between 1500-2500 rpm, then giving it throttle or going WOT, I sometimes feel a single jerk. It's like it starts accelerating for half a second, then stops for split of a second, then accelerating like normal (though boost is not perfectly smooth).
- It doesn't do it everytime, sometimes softer, sometimes harder.
- When engine is cold it's doing it more.
- I don't really feel it on stock map
- When going for a stronger tune with more boost it's doing it more

I'm running MHD, no JB4. Stage 1 since about a year. I really started noticing it after going for a custom map by BuraQ. After the eleventh revision of the map without solving the issue, I thought something is just wrong with the map. So I went MHD Stage 2+ for testing, got back nice smooth acceleration, but then just today I felt the same jerk, pretty soft though... So I'm sure something is wrong with my car.

- 335i N54 DCT (yes we have this in Europe)
- 108'000 km (about 67k miles)
- Chargepipe, FMIC since yesterday
- NGK plugs gapped, changed about 10k miles ago
- Injectors changed about a year ago, Coils are still the first ones
- HPFP changed before I owned the car
- Holding boost of 18 psi without problems, running strong
- Never had a code thrown or misfire or something like that
- Resetted DME adaptions several times

Here are 2 logs:
http://datazap.me/u/icstyle/bq-v6
http://datazap.me/u/icstyle/mhd-stage-2

Any ideas what it could be? Boost selenoids, vac lines? Wastegates worn? Injectors going bad again? Plugs not being fine?

Would really appreciate any help...

[iCstyle]

Anyone? I just ordered 2 new boost solenoids and new vac lines, hope this solves it

[STR8-6IX]

Originally Posted by iCstyle

Hi guys

I'm fighting with a problem since some weeks/months on my car:
When I'm crusing or off throttle, between 1500-2500 rpm, then giving it throttle or going WOT, I sometimes feel a single jerk. It's like it starts accelerating for half a second, then stops for split of a second, then accelerating like normal (though boost is not perfectly smooth).
- It doesn't do it everytime, sometimes softer, sometimes harder.
- When engine is cold it's doing it more.
- I don't really feel it on stock map
- When going for a stronger tune with more boost it's doing it more

I'm running MHD, no JB4. Stage 1 since about a year. I really started noticing it after going for a custom map by BuraQ. After the eleventh revision of the map without solving the issue, I thought something is just wrong with the map. So I went MHD Stage 2+ for testing, got back nice smooth acceleration, but then just today I felt the same jerk, pretty soft though... So I'm sure something is wrong with my car.

- 335i N54 DCT (yes we have this in Europe)
- 108'000 km (about 67k miles)
- Chargepipe, FMIC since yesterday
- NGK plugs gapped, changed about 10k miles ago
- Injectors changed about a year ago, Coils are still the first ones
- HPFP changed before I owned the car
- Holding boost of 18 psi without problems, running strong
- Never had a code thrown or misfire or something like that
- Resetted DME adaptions several times

Here are 2 logs:
http://datazap.me/u/icstyle/bq-v6
http://datazap.me/u/icstyle/mhd-stage-2

Any ideas what it could be? Boost selenoids, vac lines? Wastegates worn? Injectors going bad again? Plugs not being fine?

Would really appreciate any help...

I am having a similar issue. is it more prone to happen at high RPM?

check your ignition coils and spark plugs. it could be literally one or two faulty units causing it.

[iCstyle]

No it's only when cruising at lower rpm. I can run it all day WOT to redline without any problems. Spark plugs are already new. Don't know if ignition coils can cause this at lower rpm?

[blown07]

Originally Posted by iCstyle

No it's only when cruising at lower rpm. I can run it all day WOT to redline without any problems. Spark plugs are already new. Don't know if ignition coils can cause this at lower rpm?

Well yes this is when the engine will see the highest load and the greatest possibility for a misfire...at low rpm then going wot without a downshift. The same thing will happen to my car if I go WOT and don't allow a down shift when in 4th or 5th. My guess is it's a single misfire that doesn't get picked up by the ecu. My coils are new but I'm due for a plug change. This thread has actually pointed me towards a misfire as opposed to a small tranny slip I was thinking was a possibility.

[iCstyle]

Just wanted to report back, new Boost solenoids and new vac lines completely fixed the problem. It feels actually like driving a new engine

[MysticRob]

Originally Posted by iCstyle

Just wanted to report back, new Boost solenoids and new vac lines completely fixed the problem. It feels actually like driving a new engine

Glad you got it figured out, and thank you for the update. My eventual fix for the same thing was injectors.

I can't read logs yet (no idea what to look for) but am curious how Stage 2+ is working for you. I know the MHD doc says high flow DPs are recommended.

I need to log on my current Stage 1+FMIC tune and if everything looks good maybe try Stage 2+ and relog...

I live in a highly populated area and don't road or course race, using the power for short bursts only.

[iCstyle]

Unfortunately I felt the jerk again today, whereas it was only very light...

How was the problem on your car, can you describe it? I changed all my injectors about 1 year ago to index 09, I don't hope they are the reason again?

I really like Stage 2+, it's more smooth than Stage 1(+). The power it makes is really awesome. I don't have DPs, though I have an upgraded FMIC.

[MysticRob]

Originally Posted by iCstyle

Unfortunately I felt the jerk again today, whereas it was only very light...

How was the problem on your car, can you describe it? I changed all my injectors about 1 year ago to index 09, I don't hope they are the reason again?

I really like Stage 2+, it's more smooth than Stage 1(+). The power it makes is really awesome. I don't have DPs, though I have an upgraded FMIC.

Newest index 12s came out ~2013. Why index 9? Were your 9s used, or new and never installed before a year ago? I ask because anytime I find a part being redesigned multiple times that's the first thing I suspect, and I wouldn't trust used (and redesigned) parts at all.

My issue was mainly very noticeable stumbling when cold at all RPMs, but even when warmed up I still noticed some stumbling, though greatly reduced, at lower speeds and RPMs. Everything helped a bit, and added up to better driveability once I did each of them, but it was the new index 12 injectors that finally cured all ills.

And the transmission not shifting smoothly at those lower speeds made it even worse for me. Again, 134k miles and never changed according to dealership or carfax records. And the plastic drain plug was stripped out on the BMW-labeled transmission pan, so if the fluid was ever changed the pan sure wasn't. LOL
The tranny would hold onto a lower gear much longer than it I knew it should've, and when combined with a harder than anticipated shift into the next gear, it caused a jerky, peaky, driving feeling. As soon as I changed the fluid and pan filter that was no longer a problem. Shifts at lower speeds are almost imperceptible now, and occur at much lower RPMs for light throttle application, exactly how I knew these transmissions should shift (driven many lower mileage 335i's before I bought this one).

I'll add that the peaky driving feeling was still present, though greatly reduced, with the linear throttle mapping enabled in the MHD tune prior to the transmission fluid change. Now that everything is perfect I still have linear mapping enabled because of the increased boost and power, which otherwise causes whiplash when the power comes on so early -- something like 80% of power is applied at 40% throttle in the stock throttle mapping, so that jerky, light-speed feeling gets exacerbated with the added power.

[MysticRob]

Originally Posted by MysticRob

Glad you got it figured out, and thank you for the update. My eventual fix for the same thing was injectors.

I can't read logs yet (no idea what to look for) but am curious how Stage 2+ is working for you. I know the MHD doc says high flow DPs are recommended.

I need to log on my current Stage 1+FMIC tune and if everything looks good maybe try Stage 2+ and relog...

I live in a highly populated area and don't road or course race, using the power for short bursts only.

Well, when all else fails RTFM. I looked thru the MHD flasher manual again and it specifically said:
We advise against using Step up MAP on cars without the recommended parts if using for track days and sustained aggressive driving.
So it sounds like I can run Stage 2+FMIC and just do my typically short full-throttle runs without any problems, assuming my Stage 1+ logs look good. For just $49 more, why not?

[Stroker1]

I had a similar issue with my 07 manual. When i aggressively opened throttle there was a momentary stumble after which it ran fine. My primary lambda sensors were original at over 100k miles so i decided to replace them. as o2 sensors age response time increases. Solved the issue for me.. all around drivability is much better as well.

[iCstyle]

MysticRob :

I have to admit the injectors were used. I had the problem with an injector stuck open and needed fast replacement because I'm DD my car. A friend of mine who works at BMW dealership had a set of 09's with 30k miles from a 1M. They changed them but the issue was something else, so I could have them really cheap. I thought why not, problem was fixed. I'm driving with them since about 20k miles now.

As of your description I'm 99% sure it is injectors. Today it was colder, and I felt the jerks/stumbling more again. I also feel that peaky driving, even though I'm running linear throttle since MHD was released. I won't change them out right now though since the car otherwise runs just perfect.

I would just try out Stage 2+, 49$ is nothing... Log/monitor it and look at IAT, AFR and timing corrections. If they're all good I wouldn't worry to drive it daily.

[STR8-6IX]

Originally Posted by MysticRob

Glad you got it figured out, and thank you for the update. My eventual fix for the same thing was injectors.

I can't read logs yet (no idea what to look for) but am curious how Stage 2+ is working for you. I know the MHD doc says high flow DPs are recommended.

I need to log on my current Stage 1+FMIC tune and if everything looks good maybe try Stage 2+ and relog...

I live in a highly populated area and don't road or course race, using the power for short bursts only.

Originally Posted by iCstyle

Unfortunately I felt the jerk again today, whereas it was only very light...

How was the problem on your car, can you describe it? I changed all my injectors about 1 year ago to index 09, I don't hope they are the reason again?

I really like Stage 2+, it's more smooth than Stage 1(+). The power it makes is really awesome. I don't have DPs, though I have an upgraded FMIC.

I am experiencing the same issue at low rpms, and the problem is getting worse. it seems OK once the engine is warm, and I can redline no problem.

I am suspecting that this is either injectors or ignition coils. what do you guys think? should I get it scanned and just replace the part right away or should i try running fuel system/injector cleaner and see if this solves my problem? (if it is injectors)

also, I get a drivetrain malfunction due to this problem. for some reason it occurs when upshifting aggressively (past 4000RPM) and staying on the throttle in between shifts. it is more prone to happen in the lower gears off the line, and when the engine or ambient temps are cold. if i ease off the throttle in between shifts, the problem does not really occur. I am also getting some low rpm stuttering.

[MysticRob]

Originally Posted by STR8-6IX

I am experiencing the same issue at low rpms, and the problem is getting worse. it seems OK once the engine is warm, and I can redline no problem.

I am suspecting that this is either injectors or ignition coils. what do you guys think? should I get it scanned and just replace the part right away or should i try running fuel system/injector cleaner and see if this solves my problem? (if it is injectors)

also, I get a drivetrain malfunction due to this problem. for some reason it occurs when upshifting aggressively (past 4000RPM) and staying on the throttle in between shifts. it is more prone to happen in the lower gears off the line, and when the engine or ambient temps are cold. if i ease off the throttle in between shifts, the problem does not really occur. I am also getting some low rpm stuttering.

If you haven't seen this thread, it's invaluable: http://www.e90post.com/forums/showthread.php?t=631829

Take an inventory of what parts are still installed and go from there. How many miles on the engine and current parts? How many miles on replacement parts, if any? What index are the injectors?

In my case it was normally mild misfiring when cold and in lower RPMs, though the blown injector on #4 was the death blow, as the engine wouldn't even idle correctly after that. The ultimate solution was new index 12 injectors, but doing the plugs (~25k since last change), coils (likely all original), and walnut blasting (no record of it being done in BMW system) all helped incrementally. Little things added up in my case till the ultimate failure.

I changed the vacuum lines and checked the boost solenoids just for peace of mind, and found a couple slow leaking lines due to age and brittleness. Don't think it affected performance yet though, as the leaks were slow and boost looked normal on logs.

If you don't have a handheld tuner get the MHD android app and buy the flasher and monitor modules so you can log and check for codes. Between that and the typical issues, you should be able to narrow it down. Sucks that so many things can cause the same problems like misfires, and that it could be just one big thing, or a few small things altogether. Lots of variables to deal with for sure. With 134k miles, I had a good hunch it was likely a bunch of stuff adding up, but with lower mileage it could be just one or two things.

[STR8-6IX]

Originally Posted by MysticRob

If you haven't seen this thread, it's invaluable: http://www.e90post.com/forums/showthread.php?t=631829

Take an inventory of what parts are still installed and go from there. How many miles on the engine and current parts? How many miles on replacement parts, if any? What index are the injectors?

In my case it was normally mild misfiring when cold and in lower RPMs, though the blown injector on #4 was the death blow, as the engine wouldn't even idle correctly after that. The ultimate solution was new index 12 injectors, but doing the plugs (~25k since last change), coils (likely all original), and walnut blasting (no record of it being done in BMW system) all helped incrementally. Little things added up in my case till the ultimate failure.

I changed the vacuum lines and checked the boost solenoids just for peace of mind, and found a couple slow leaking lines due to age and brittleness. Don't think it affected performance yet though, as the leaks were slow and boost looked normal on logs.

If you don't have a handheld tuner get the MHD android app and buy the flasher and monitor modules so you can log and check for codes. Between that and the typical issues, you should be able to narrow it down. Sucks that so many things can cause the same problems like misfires, and that it could be just one big thing, or a few small things altogether. Lots of variables to deal with for sure. With 134k miles, I had a good hunch it was likely a bunch of stuff adding up, but with lower mileage it could be just one or two things.

ive got just under 120k (KM) on the motor, no replacement parts. I need to find a mechanic shop that can scan for stored codes to figure this out. do you think it is a coil pack or injector, or is impossible to tell without scanning first?

[MysticRob]

Originally Posted by STR8-6IX

ive got just under 120k (KM) on the motor, no replacement parts. I need to find a mechanic shop that can scan for stored codes to figure this out. do you think it is a coil pack or injector, or is impossible to tell without scanning first?

Well that's the thing, those individual parts can cause problems, and those problems can be bad enough to throw a code (or may not, but you'll still feel it). The problem is the code is merely a symptom of something that can be monitored, and it won't actually point specifically to a given part. Misfires can occur singularly from bad plugs, coils, or injectors, or from a mix of any/all of those 3.

Are you tuned at all? Any aftermarket parts?
My Dad was a mechanic so I learned my way around engines early, but there's a wealth of info on these cars now, and you can download service manuals to figure most things out on your own. I simply don't trust most shops or dealerships to do the job correctly when I know I can do most things myself with a manual AND I actually care about the car and people driving it!

I doubt you have the original plugs at the equivalent of 75k miles. If so, that would definitely be a problem since BMW recommends changing plugs at 45k miles, obviously less if you're tuned. At that mileage coils can definitely be an issue if original. Same with injectors. Same with the intake valve build-up, though again how good or bad any build-up is (like misfires) is merely a symptom of many other variables causing it (sustained high RPMs, bad PCV system, leaky turbo seals, etc).

[STR8-6IX]

Originally Posted by MysticRob

Well that's the thing, those individual parts can cause problems, and those problems can be bad enough to throw a code (or may not, but you'll still feel it). The problem is the code is merely a symptom of something that can be monitored, and it won't actually point specifically to a given part. Misfires can occur singularly from bad plugs, coils, or injectors, or from a mix of any/all of those 3.

Are you tuned at all? Any aftermarket parts?
My Dad was a mechanic so I learned my way around engines early, but there's a wealth of info on these cars now, and you can download service manuals to figure most things out on your own. I simply don't trust most shops or dealerships to do the job correctly when I know I can do most things myself with a manual AND I actually care about the car and people driving it!

I doubt you have the original plugs at the equivalent of 75k miles. If so, that would definitely be a problem since BMW recommends changing plugs at 45k miles, obviously less if you're tuned. At that mileage coils can definitely be an issue if original. Same with injectors.

would changing injectors/ignition coils/spark plugs improve performance or efficiency? I am almost certain that all of those parts or original, will need to change soon. I am stock.

[MysticRob]

Originally Posted by STR8-6IX

would changing injectors/ignition coils/spark plugs improve performance or efficiency? I am almost certain that all of those parts or original, will need to change soon. I am stock.

I updated my original post that you quoted above a bit (included intake valve issues, etc), but yes, replacing some or all of those parts could definitely help IF those specific parts are causing the issues. No way to tell if they would though. There's just no way of knowing without actually doing the work and seeing if the problem still exists or has been resolved. And whether they cause problems is determined by a lot of variables.

Example: Maybe those parts at 75k miles just aren't that bad if it's Grandma's highway car droning along at 1800RPM @ 55MPH. More a problem if it's beat on constantly on local roads or raced.

Check for codes to hopefully narrow down which cylinder the problem is on. Swap coils between cylinders and see if the problem follows the coil. Maybe it's just one coil. Maybe it's just one plug, etc, but they're so cheap might as well do them all. Code check is best way to narrow down which cylinder the issue may be in. If money isn't a concern and you're absolutely certain you're still on the original plugs and coils, maybe swap them all out and see if the problem still exists. Those are the cheapest parts and easiest to change out.

If issues remain, look into walnut blasting the intake valves. Again, cheaper than the last typical issue, which is the injectors. I did plugs, coils, injectors, and walnut blasted the intake valves myself after searching for the best parts deals for less than $1200 all in, including new intake and throttle body gaskets after the walnut blasting (I had the air compressor already). Having a shop or dealership do all that would've been cost prohibitive to owning the car IMHO, likely north of $4k or more (honestly don't know since I do it all myself).

[STR8-6IX]

Originally Posted by MysticRob

I updated my original post that you quoted above a bit (included intake valve issues, etc), but yes, replacing some or all of those parts could definitely help IF those specific parts are causing the issues. No way to tell if they would though. There's just no way of knowing without actually doing the work and seeing if the problem still exists or has been resolved. And whether they cause problems is determined by a lot of variables.

Example: Maybe those parts at 75k miles just aren't that bad if it's Grandma's highway car droning along at 1800RPM @ 55MPH. More a problem if it's beat on constantly on local roads or raced.

Check for codes to hopefully narrow down which cylinder the problem is on. Swap coils between cylinders and see if the problem follows the coil. Maybe it's just one coil. Maybe it's just one plug, etc, but they're so cheap might as well do them all. Code check is best way to narrow down which cylinder the issue may be in. If money isn't a concern and you're absolutely certain you're still on the original plugs and coils, maybe swap them all out and see if the problem still exists. Those are the cheapest parts and easiest to change out.

If issues remain, look into walnut blasting the intake valves. Again, cheaper than the last typical issue, which is the injectors. I did plugs, coils, injectors, and walnut blasted the intake valves myself after searching for the best parts deals for less than $1200 all in, including new intake and throttle body gaskets after the walnut blasting (I had the air compressor already). Having a shop or dealership do all that would've been cost prohibitive to owning the car IMHO, likely north of $4k or more (honestly don't know since I do it all myself).

I have a port injected, naturally aspirated n52. walnut blasting is more for direct injected motors. as for the plugs/injectors, I will get that scanned this week and hopefully figure it out. I can tell that the coils are original, they look old, are covered in a good amount of dust and they are all the same so I know none have been replaced down the road.

thanks for the help!

[MysticRob]

Originally Posted by STR8-6IX

I have a port injected, naturally aspirated n52. walnut blasting is more for direct injected motors. as for the plugs/injectors, I will get that scanned this week and hopefully figure it out. I can tell that the coils are original, they look old, are covered in a good amount of dust and they are all the same so I know none have been replaced down the road.

thanks for the help!

LOL, I never even looked at your vehicle type, just assumed since you're in the N54 forum. Yeah, so disregard that then!
I take it you bought it used. And since you own an N52 I have no idea what the plug change interval is for it.

[STR8-6IX]

Originally Posted by MysticRob

LOL, I never even looked at your vehicle type, just assumed since you're in the N54 forum. Yeah, so disregard that then!
I take it you bought it used. And since you own an N52 I have no idea what the plug change interval is for it.

its every 60k (miles) I did buy it used so i am not sure if the plugs have been changed, but i bought the car at 37k (miles) so i highly doubt it.