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Old 01-30-2017, 08:48 PM   #1
bayos04
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"Pulsing" or "surging" in 3rd gear

I have been searching and I can't figure out what is causing my issue, but I may be searching for the wrong thing...

This sprung up a week ago. Under moderate acceleration, approx 60% to WOT, I get a pulsing, like when you are just learning to drive a stick and you dump the clutch without enough throttle and the car jumps, pauses, jumps, pauses. Not nearly that extreme, but same feeling (is that the clutch slipping?). This only happens in 3rd gear, over 2500 RPM right up to redline. Nothing in 1st or 2nd. I haven't been able to get out to a quiet highway to check 4th or 5th. Also it doesn't happen every time, just most of the time.

This seems similar, but not the same as, some VANOS issues I have found.

Is it the SAC starting to fail? Again, this doesn't seem right as it only happens in third.

Car is an 04 330 ZHP with 55k miles on it, obviously a 6 speed, no mods.

Thoughts?
Opinions?

Thanks
James



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Old 01-30-2017, 09:46 PM   #2
BaliDawg
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Can you make it happen when sitting still in neutral and just revving the engine?

Start by reading the trouble codes.

It sounds a bit like the infamous 2800 RPM stutter, except that clears up at 3000 RPMs.

How old is your fuel pump?
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Old 01-30-2017, 09:56 PM   #3
bayos04
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No hesitation at all in neutral, revs smoothly.

No trouble codes, but all I have is a generic OBDII scan tool. Not sure if that is good enough.

Fuel pump is original AFAIK, I have only owned the car for a year. But seeing as it is RPM and gear specific I'm doubtful that is the issue, but I have been wrong before....


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Old 01-30-2017, 10:11 PM   #4
BaliDawg
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Quote:
Originally Posted by bayos04 View Post
No hesitation at all in neutral, revs smoothly.

No trouble codes, but all I have is a generic OBDII scan tool. Not sure if that is good enough.

Fuel pump is original AFAIK, I have only owned the car for a year. But seeing as it is RPM and gear specific I'm doubtful that is the issue, but I have been wrong before....
Get an ELM327 wireless OBD adapter and OBD Fusion app for your iPad. These tools will show you a lot about your engine.

If the fuel pump really is original, it is long overdue for replacement.
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Old 01-30-2017, 11:46 PM   #5
topher339
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Check your fuel pump pressure. It doesn't sound too likely but it might be the problem. When mine started to soft fail I would get bucking and surging and the car felt like is was running on 100hp instead of 333. Anything above around 3k rpm would cause it. Never threw any codes either. Maybe yours is failing very, very softly. You should be getting around 72psi when the pump has been primed for start, if I remember correctly.

If you end up getting a new pump, I highly recommend getting a Walbro pump installed using a radium engineering kit. Smaller and stronger than OEM and supposedly longer lasting. (I'm assuming the intake pump is replaceable much like in the M3)

Last edited by topher339; 01-30-2017 at 11:48 PM. Reason: suggestion for new fuel pump model
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Old 01-31-2017, 12:53 AM   #6
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Quote:
Originally Posted by topher339 View Post
Check your fuel pump pressure. It doesn't sound too likely but it might be the problem. When mine started to soft fail I would get bucking and surging and the car felt like is was running on 100hp instead of 333. Anything above around 3k rpm would cause it. Never threw any codes either. Maybe yours is failing very, very softly. You should be getting around 72psi when the pump has been primed for start, if I remember correctly.

If you end up getting a new pump, I highly recommend getting a Walbro pump installed using a radium engineering kit. Smaller and stronger than OEM and supposedly longer lasting. (I'm assuming the intake pump is replaceable much like in the M3)
Non-M E46s, such as OP's 2004 330i ZHP, should see 50 PSI at the fuel rail. The fuel pump is different than your M3, and Siemens/VDO is the OEM.
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Old 01-31-2017, 01:09 AM   #7
topher339
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Originally Posted by BaliDawg View Post
Non-M E46s, such as OP's 2004 330i ZHP, should see 50 PSI at the fuel rail. The fuel pump is different than your M3, and Siemens/VDO is the OEM.
In that case, check for 50psi. Should be fairly easy since non-M has a fuel rail on the engine.
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Old 01-31-2017, 04:34 PM   #8
bayos04
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Update....
Fuel pressure is 50 psi across the board. At idle, at 3000 rpm, during an rpm sweep. Rock solid at 50.

I managed to get out on a quite highway today. It took multiple 1st to 4th runs for it to show up, even in 3rd and when it did it also showed in 4th, same RPM range.

I realized the only time this really shows up is on my drive home where I am in stop and go traffic for 10 to 15 minutes then 10 minutes of almost freeway where I open it up and can "play" a bit. So it only happens when the car is hot and I have been shifting a lot.

Clutches overheating??? Still doesn't explain why 1st and 2nd are solid.

Thoughts?

Veepeak scanner tool is on the way. Should be here Friday....


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Old 01-31-2017, 06:00 PM   #9
topher339
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Odd. You could check the throttle positions sensors. I wouldn't think they are the problem but they can cause pulsing and hesitation when they go bad. Usually, it's in every gear, though. Often the EML comes on, too. I'm not sure how the non-M throttle system compares to an M car.

From my understanding of it, clutch slip wouldn't really cause surging as much as poor acceleration and having to shift sooner than usual. If your clutch is overheating, you should be able to smell it. Could be wrong, though.

Last edited by topher339; 01-31-2017 at 06:01 PM.
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Old 01-31-2017, 08:14 PM   #10
bayos04
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I agree topher, thus my confusion. It just doesn't add up.

Good call on the throttle position sensor. I will test that as soon as I figure out how....


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Old 01-31-2017, 08:29 PM   #11
topher339
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This thread does a pretty good job of explaining how to test the TPS. - http://www.e46fanatics.com/forum/sho...d.php?t=620400 - Granted, it's for an M car but the idea should be the same.

But, again, it usually throws codes and limp mode. Really not sure what else it could be. Bimmers can be so very temperamental.
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Old 01-31-2017, 08:44 PM   #12
bayos04
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Cool thanks

Once I have done that and done a scan with the veepeak (once it is in) I'm thinking a battery disconnect is in order. Just reset everything. Computers are wonderful things... man my 67 camaro is so much nicer to diagnose.


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Old 01-31-2017, 09:01 PM   #13
topher339
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"my 67 camaro is so much nicer to diagnose"

Ha. I was just thinking the same of my 67 Cougar. Fully mechanical vehicles are fantastic.
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Old 01-31-2017, 09:45 PM   #14
bayos04
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Cougar, nice car and fairly rare, I really like those years.

There is something really nice about being able to diagnose any electrical problem with a multi meter.


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Old 01-31-2017, 10:13 PM   #15
topher339
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Love the pre-71 models. Although, I was actually looking for a Camaro at the time... Simplicity is king with classic cars.
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Old 02-01-2017, 08:11 PM   #16
bayos04
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New discovery... played a bit more on the drive home today. I discovered that it only happens from approx 60% to 95% throttle. If I floor it the problem isn't there.

TPS still seems the most likely cause (I haven't had time to test yet) but then why doesn't it happen in 2nd or first??? Starting to think this is a computer issue... color me baffled.


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Old 02-01-2017, 08:22 PM   #17
topher339
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Very odd. Have you tried a hard reset yet (completely disconnect battery and touch the leads together to drain all power)? If it is indeed a computer problem, that just may clear it up.

And if the TPS tests as good, I really don't know what else to check.

Last edited by topher339; 02-01-2017 at 08:23 PM.
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Old 02-01-2017, 08:28 PM   #18
bayos04
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I want to wait till the veepeak shows up and I can do a full scan. Although if it isn't throwing a CEL I don't know what it could tell me. I'm not familiar with these type of scan tools and what they can do beyond a generic scan tool.


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Old 02-01-2017, 08:28 PM   #19
bayos04
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Ya if that isn't it I am out of ideas too.


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Old 02-01-2017, 09:41 PM   #20
topher339
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Apparently, there can sometimes be codes that don't cause a CEL or won't show up during a generic scan. These "hidden" codes require a BMW scanner (or so I recently read, a fancy scanner might do). I was suggested this one by another user just the other day - http://www.ebay.com/itm/1-4-0-Progra...081734&vxp=mtr . Plan to get one soonish. I hear they can be rather difficult to get started (and sometimes are virus infested) but work very well once it's up and running. Allows a lot of programming options, too (lights flash on lock, turning off auto door locking when in drive, etc.). Most of the issues stem from the fact that it's designed for Windows XP. Should be plenty of forums on how to use it.
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