[SC300T]

I have a 30k mile CPO F10 with an N55 that is having a slight occasional studder under very light throttle. It also makes tip-in a little lazy. No difference cold or hot. Any ideas? I would think injectors would be a morning sickness type of thing. It goes well under heavy throttle, but power delivery is not always super consistent. I have another 60k mile N55 car that is smooth and steady and strong, so there is definitely something that isn't 100%.

There are no check engine lights, and I'd suspect that with only 30k on the car in 5 years that it sat a bit or was city driven. The car had frequent oil changes (I just bought it).

I was thinking of having the dealer do plugs and reset adaptations for octane, etc.

Should I have them looking for VANOS / Valvetronic issues or possibly a wonky coil?

Any ideas, Thanks.

[ssgm1x]

Originally Posted by scotthureau

I have a 30k mile CPO F10 with an N55 that is having a slight occasional studder under very light throttle. It also makes tip-in a little lazy. No difference cold or hot. Any ideas? I would think injectors would be a morning sickness type of thing. It goes well under heavy throttle, but power delivery is not always super consistent. I have another 60k mile N55 car that is smooth and steady and strong, so there is definitely something that isn't 100%.

There are no check engine lights, and I'd suspect that with only 30k on the car in 5 years that it sat a bit or was city driven. The car had frequent oil changes (I just bought it).

I was thinking of having the dealer do plugs and reset adaptations for octane, etc.

Should I have them looking for VANOS / Valvetronic issues or possibly a wonky coil?

Any ideas, Thanks.

Take to bmw dealer asap. I have same exact car same miles. Dealers know exactly what this is and know these cars inside and out. Could be something stupid or may just need an Engine Management Software Update like my car needed. Took 5 hours to do and car drives 100% better and shifts better too. So do urself a favor and make that BMW Appointment.

[5soko]

I would def do the plugs to start..

Always i would still scan the car using a BMW type scanner to see if there is any shadow codes stored for any faults.

[SC300T]

A brief update...

Tuned the car with MHD Stage 1, replaced the plugs with NGKs for the N20... The issue still exists, but feels a bit different. A combination of the E30 map and the new plugs it feels more awake just off idle. When letting the clutch out around idle the engine doesn't all on its face any more. Still getting that jittery slight judder or hesitation accelerating on light throttle around 1500-3000rpm.

I suppose I could change the coilpacks. Took it to the dealer and they were useless, they said that it drove great. There are no codes and with the flash, the logs actually look decent.

I'm leaning towards some mild VANOS or Valvetronic problem. I read a post awhile back about pulling the connector to the Valvetronic motor to test to see if it runs smoother. Has anyone done this? Has anyone pulled and cleaned the VANOS system with good results?

I know its not normal, because my other N55 doesn't do it - and the two cars were built in the same factory a month apart.

Any suggestions appreciated.

[ey2001]

hows your logs?

[SC300T]

hows your logs?

I just posted one on another thread this weekend. The logs seem to be excellent - the log I posted had zero timing pulls and was 14psi tapering to 9.5 up top with 12.x A/F Ratio. Basically everything is golden when you give it the beans.

That's why I'm leaning away from spark / coil and more torwards thinking there is a VANOS or Valvetronic issue. I suppose there are tests that can be run on the valvetronic motor and you can disassemble and clean the VANOS system.

I suppose a fuel injector could be a bit iffy and hiccupping at low throttle. I need to do some light throttle logs to see if anything shows up there. There is a hint of morning sickness (just a slight wobble at idle at startup that quickly goes away), but I've heard that lots of N55s do this and my other car N55, which runs perfect also does this.

I'm really at a loss. If it were an N54, I'd do walnut blasting.

[ssgm1x]

Originally Posted by SC300T

I have a 30k mile CPO F10 with an N55 that is having a slight occasional studder under very light throttle. It also makes tip-in a little lazy. No difference cold or hot. Any ideas? I would think injectors would be a morning sickness type of thing. It goes well under heavy throttle, but power delivery is not always super consistent. I have another 60k mile N55 car that is smooth and steady and strong, so there is definitely something that isn't 100%.

There are no check engine lights, and I'd suspect that with only 30k on the car in 5 years that it sat a bit or was city driven. The car had frequent oil changes (I just bought it).

I was thinking of having the dealer do plugs and reset adaptations for octane, etc.

Should I have them looking for VANOS / Valvetronic issues or possibly a wonky coil?

Any ideas, Thanks.

Originally Posted by SC300T

I have a 30k mile CPO F10 with an N55 that is having a slight occasional studder under very light throttle. It also makes tip-in a little lazy. No difference cold or hot. Any ideas? I would think injectors would be a morning sickness type of thing. It goes well under heavy throttle, but power delivery is not always super consistent. I have another 60k mile N55 car that is smooth and steady and strong, so there is definitely something that isn't 100%.

There are no check engine lights, and I'd suspect that with only 30k on the car in 5 years that it sat a bit or was city driven. The car had frequent oil changes (I just bought it).

I was thinking of having the dealer do plugs and reset adaptations for octane, etc.

Should I have them looking for VANOS / Valvetronic issues or possibly a wonky coil?

Any ideas, Thanks.

I have similar issue now. I did fmic/ Plugs .025 gap/Coils/new battery and afterwards I got a rough idle with slight lag at tip in. Pressure tested with no leaks. Currently troubleshooting it and it's driving me crazy. Will be replacing plugs and coils again with stock gap this time. Also gonna clean MAP sensor. Will report back !!!!

[SC300T]

I have similar issue now. I did fmic/ Plugs .025 gap/Coils/new battery and afterwards I got a rough idle with slight lag at tip in. Pressure tested with no leaks. Currently troubleshooting it and it's driving me crazy. Will be replacing plugs and coils again with stock gap this time. Also gonna clean MAP sensor. Will report back !!!!

When I replaced the plugs with NGK 5992s gapped to .020 it improved the idle response - You would see this on a 6MT when letting out the clutch slowly at idle, the engine has far better response and oomph to pull the car out of idle and accelerate, and letting the clutch out drags the engine down less. They did not affect the notchy response in the 2k range where it feels like there are little surges and flat spots in the response.

I'm thinking I may want to pull the electrical connector to the Valvetronic motor to put the car back in "throttle body" mode to see if that clears it up. My thought is that a failing valvetronic motor could be the culprit. I hear there is a thorough test they can do on the valvetronic motor, that fully excercies it and tests its response.

[wcr3d]

Yes there are tests.
Mine wasn't rough just low power at low rpm.
It finally through CEL and I took it in.
They had it for days running the standard protocols.
My SA was keeping me informed, which I greatly appreciate.
It was all pointing to valvetronic, so first they replaced the harness.
Then the servo motor, then stripping it down totally.
Finally said the cam on the eccentric shaft ( I think it's called) slipping.
I would hate to say the actual cost but would guess at 5k+,
This paid for the cost of CPO and my out of pocket was $50.
Anyway it was the fix to my problem.

[thakid22]

Originally Posted by SC300T

I have a 30k mile CPO F10 with an N55 that is having a slight occasional studder under very light throttle. It also makes tip-in a little lazy. No difference cold or hot. Any ideas? I would think injectors would be a morning sickness type of thing. It goes well under heavy throttle, but power delivery is not always super consistent. I have another 60k mile N55 car that is smooth and steady and strong, so there is definitely something that isn't 100%.

There are no check engine lights, and I'd suspect that with only 30k on the car in 5 years that it sat a bit or was city driven. The car had frequent oil changes (I just bought it).

I was thinking of having the dealer do plugs and reset adaptations for octane, etc.

Should I have them looking for VANOS / Valvetronic issues or possibly a wonky coil?

Any ideas, Thanks.

Before you get too deep into chasing this issue, try running a couple bottles of Techron Complete Fuel System Treatment through the gas tank. In my experience (N52, N54, N55) even slightly dirty injectors can cause issues at idle, just off idle, and with throttle response/tip-in. Techron is pretty good at curing this... until it gets dirty again.

About injectors causing morning sickness... They will, when they are leaky. However, when the issue is clogging or deposits, you will have symptoms morning, noon, and/or night.

[SC300T]

Before you get too deep into chasing this issue, try running a couple bottles of Techron Complete Fuel System Treatment through the gas tank.

I'll do that this weekend... Thanks for the suggestion!

[thakid22]

Originally Posted by SC300T

I'll do that this weekend... Thanks for the suggestion!

Let us know how it works.
I throw a bottle into an almost empty gas tank (3 gallons or so).
Then I drive that little bit of gas/ Techron out and fill up the tank while adding another bottle to the full tank... Gets the injectors nice and clean. Quite quickly too.