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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Diagnose my issue: N52 Fluctuating Power



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      04-24-2010, 05:46 PM   #1
e90ben
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Diagnose my issue: N52 Fluctuating Power**FIX FOUND**

Just picked up a CPO 330i, and have been happy with it so for minus this one issue.

The cars seems to have issues cruising around town or hwy in 3,4,5,6 gear at around 2000-3000 rpm.
The best way for me to describe the issue is, the car thinks that I'm pressing and removing my foot from the accelerator in 1/4 throttle increments.

Almost seems like its surging....power on, power off.

The crazy thing is, if I WOT there is absolutely no surging

Any thoughts or suggestions about the issue?

Software?
Vanos?

-------------------------------------------------------------------------------

COLES NOTES

Decided to update the original post

Havent had time to take it to the dealer, so I still have the issue.


I've been able to put a few more miles and here are the coles notes of the symptoms and its Ive replaced.

Replaced:
Valvetronic motor- No fix
Air Filter- No Fix
Charcoal Filter- No Fix
Fuel Injector Cleaner- No Fix

Symptoms:

Light throttle pressure to maintain with speed with traffic- slight stutter
1/2 throttle- feels like a misfire
WOT- Nothing


Fix: Found out that the previous owner had a BMS PBX installed in it. The issues was a faulty Pedal Position. Sensor.

Last edited by e90ben; 06-10-2010 at 09:00 AM.
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      04-24-2010, 07:52 PM   #2
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I'm not sure what you mean by the 1/4 throttle increments but the mpg gauge in my 330 sometimes goes down to 12mpg then back to 50+mpg when feathering the throttle at low speeds....like when coming to and starting from a stop. Our cars have adaptive throttles which means they learn the way the drivers drive and will adjust settings appropriately. You can reset the "memory" by inserting your key fob into the slot and turning on the ACC power. 2 clicks, no foot on brake. Hold the accelerator pedal down for 25-30 seconds. You may or may not hear a noise coming from the vehicle. People say it is the transmission resetting itself but I think people just hear things coincidentally. The transmission is not a computer it is controlled by one. Turn the car back off. Take out and reinsert your key fob, start it up as normal and drive it around. See if this helps. GL.
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      04-24-2010, 08:26 PM   #3
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Trip to the dealer. My MPG gauge does the same. Sometimes when I'm at idle my motor almost stalls, been doing that since new....

Put in some fuel injector cleaner, drive around, if that doesn't help take it to the dealer
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      04-24-2010, 08:30 PM   #4
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Quote:
Originally Posted by Aonarch View Post
Trip to the dealer. My MPG gauge does the same. Sometimes when I'm at idle my motor almost stalls, been doing that since new....

Put in some fuel injector cleaner, drive around, if that doesn't help take it to the dealer
Wait so fuel is actually being delivered when the gauge freaks out? I don't get how you're almost stalling. Also what fuel injector cleaner do you use? I just hit 52k and I think fuel injector cleaner would be a good idea.
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      04-24-2010, 08:40 PM   #5
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Quote:
Originally Posted by ********* View Post
I'm not sure what you mean by the 1/4 throttle increments but the mpg gauge in my 330 sometimes goes down to 12mpg then back to 50+mpg when feathering the throttle at low speeds....like when coming to and starting from a stop. Our cars have adaptive throttles which means they learn the way the drivers drive and will adjust settings appropriately. You can reset the "memory" by inserting your key fob into the slot and turning on the ACC power. 2 clicks, no foot on brake. Hold the accelerator pedal down for 25-30 seconds. You may or may not hear a noise coming from the vehicle. People say it is the transmission resetting itself but I think people just hear things coincidentally. The transmission is not a computer it is controlled by one. Turn the car back off. Take out and reinsert your key fob, start it up as normal and drive it around. See if this helps. GL.
Thanks for the information. Ill give it a shot and see.

What I mean by 1/4 throttle increments is it seems like someone is slightly tapping on an off the gas pedal....but my foot is not moving...


I went to the dealer to book a appointment and the SA thinks is a bad ignition coil

What are the symptoms of a bad fuel pump? or bad MAF?

I might unplug the MAF and see what happens. If I do that does the car run in closed loop?
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      04-24-2010, 09:47 PM   #6
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Quote:
Originally Posted by e90ben View Post
Thanks for the information. Ill give it a shot and see.

What I mean by 1/4 throttle increments is it seems like someone is slightly tapping on an off the gas pedal....but my foot is not moving...


I went to the dealer to book a appointment and the SA thinks is a bad ignition coil

What are the symptoms of a bad fuel pump? or bad MAF?

I might unplug the MAF and see what happens. If I do that does the car run in closed loop?
Since your car has 52k on it you might as well do these following things: clean your MAF with MAF cleaner and use fuel injector cleaner (Chevron/ STP/ any major brand will work).

It is vital to use fuel injector cleaner every 5k or so, BMW actually recommends it and sells their own stuff. It helps clean the VANOS, which could be an issue in your case.
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      04-24-2010, 10:10 PM   #7
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Interesting. I'm having the same issue in my 325i (330i conversion) but I'm attributing that to my aftermarket software. Mine kicks in at about 3500 rpm and will take about 2 seconds to get full throttle when I actually hit the gas.
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      04-24-2010, 10:37 PM   #8
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Quote:
Originally Posted by e90ben View Post
Thanks for the information. Ill give it a shot and see.

What I mean by 1/4 throttle increments is it seems like someone is slightly tapping on an off the gas pedal....but my foot is not moving...


I went to the dealer to book a appointment and the SA thinks is a bad ignition coil

What are the symptoms of a bad fuel pump? or bad MAF?

I might unplug the MAF and see what happens. If I do that does the car run in closed loop?
Ahh you know what I've been noticing this too. Except this only happens when I'm in Step and let go of the throttle when in high rpms and try to lightly tap the throttle. It feels like it's "choking" but it's just that in higher rpms the throttle is more sensitive. I think resetting the throttle will help a bit. It could be a bad ignition coil and this maybe be something I might have to look into too.
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      04-25-2010, 08:20 AM   #9
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Just a thought...since timing is controlled electronically maybe you have a dying ignition coil?? My rpm's used stutter at idle like that until one day one of my cylinders was flat out misfiring. Turned out to be igntion coil. Ordered from tishcer changed it out in 30 min. All good
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      04-25-2010, 03:11 PM   #10
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Quote:
Originally Posted by hotnikks View Post
Just a thought...since timing is controlled electronically maybe you have a dying ignition coil?? My rpm's used stutter at idle like that until one day one of my cylinders was flat out misfiring. Turned out to be igntion coil. Ordered from tishcer changed it out in 30 min. All good

See thats the thing, at idle or WOT the symptom is not there. I would assume that if it is a bad coil/Sparkplug it would be more pronounced at WOT..


I did try the Throttle Body Alignment, and I thought it had fixed the issue as there was absolutely not surging. However after getting on the throttle for a few quick stoplight to stoplight runs, it came back.


Cars booked for an appointment on thursday, so if anyone can point me in a direction to talk about with the SA it would be much appreciated
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      04-30-2010, 12:10 PM   #11
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Quote:
Originally Posted by e90pilot View Post
Interesting. I'm having the same issue in my 325i (330i conversion) but I'm attributing that to my aftermarket software. Mine kicks in at about 3500 rpm and will take about 2 seconds to get full throttle when I actually hit the gas.
I was just reading your post and that's exactly what mine is doing, except I'm stock.

Cars at the dealer now getting looked at. Wish the DAMN SA would return my calls or give me a courtesy call back telling me whats going on
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      04-30-2010, 03:56 PM   #12
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Update:

Finally got a call back from the SA. He told me that they think that the Valvetronic motor is dead/faulty.

He also told me that this may or may not be covered under CPO?

Anyone know if this is the case? Ive looked over my CPO certificate and it makes no mention of Valvetronic motor, but does mention Valvetronic Sensor. I assume that it would be covered under the parts of the Cylinder head?
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      05-05-2010, 01:40 PM   #13
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Update:

So the issue appears to have been resolved with the Valvetronic Motor replacement.

Drove the car around 20 kms, and there are not hesitations or surges of power. As I put more miles on the car ill report back

You guys experiencing this, might want to take your car in for service before warranty is up...as CPO doesn't cover the motor
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      05-06-2010, 06:49 PM   #14
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Update:

This AM, when driving the car around the car began to hesitate and developed slight buck when applying slight throttle. It subsided a bit the harder and longer I drove the car.

Thinking I would get under the hood and peek around, I then decided to throw in a K&N filter.

When I removed the stock filter is was in 1/2 decent condition with the bottom of the Airbox littered with stones/leaves.....etc.

Went out for a short test drive and there is no hesitation or bucking!!

I will continue to update this thread(Even though I'm the only one reading this) with any new updates
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      05-06-2010, 06:56 PM   #15
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Why dosen't CPO cover that? I thought CPO covered the entire drivetrain for 100k
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      05-06-2010, 07:13 PM   #16
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Quote:
Originally Posted by index1489 View Post
Why dosen't CPO cover that? I thought CPO covered the entire drivetrain for 100k
Its not one of the parts that is listed on the "CPO" document

BMW NA confirmed this as well

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      05-06-2010, 07:24 PM   #17
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have you checked the intake hose from the airfilter housing to the throttle body? the round hose with the clamps.
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      05-06-2010, 10:26 PM   #18
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Quote:
Originally Posted by mike3000fl View Post
have you checked the intake hose from the airfilter housing to the throttle body? the round hose with the clamps.
I didnt, when I reinstalled the K&N I made sure that it Popped back in on the top and bottom

Maybe that was it..
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      05-13-2010, 03:01 PM   #19
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Update:

Issue has been resolved.

Looks like it takes some time for the car to adapt and reset the Short Term Fuel trims and the Long Term Fuel Trims.
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      05-14-2010, 04:45 PM   #20
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I can't believe this isn't covered under the warranty. Link to BMWNA service bulletin anyone??
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      05-15-2010, 12:29 PM   #21
e90ben
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Update:

Went for a drive on the highway today and discovered a couple of things.

While on the highway, the stuttering/misfiring came back with a vengeance.

Here are the symptoms:

Light peddle pressure, enough to keep pace with traffic produced the stuttering

Medium peddle pressure, produced stuttering through the rev range.

WOT produced less stuttering but the car seemed down 20 hp or so.

Now the strange thing is, if I set the cruise control it all stops....


So, Im thinking its now the TPS or Pedal position sensor.

Does anyone know if either of these cause a code to be thrown?
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      05-15-2010, 03:32 PM   #22
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With a TPS, you'll get a code usually when it sends a null value to the ECU when it's not supposed to. If it's sending data, it's really hard for a computer to figure out if the data is bad. Programmers usually put limits to data parameters so once they exceed set values the computer assumes it's an error. If the data remains within the set values the car will not report any problems even though the might exist.
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