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Discussion Starter #1
I have a 2002 320i with a mechanical/technical problem that has yet to be properly diagnosed (despite significant effort). Symptoms are as follows:

- While driving with RPM between approximately 1500 and 2500 the tachometer will bounce up and down between approximately 1200 and 2000 RPM. This usually happens when the car is traveling at a constant rate of speed and has to slightly increase RPM to maintain that speed (e.g. when climbing a small hill). Also seems to happen when the car should upshift into a higher gear.

- While at highway speed when I push my foot on the accelerator the RPMs will go up slightly but will then dip dramatically. Once the dip happens the car will sometimes gradually gain RPM and speed and return to a normal driving dynamic; other times the RPM jumping as noted in my first point will occur until I either ease off on the gas, or floor the pedal and push the RPMs much higher.

- While accelerating at highway speeds the RPMs are inconsistent - the tachometer wavers and moves up and down. This is especially noticeable when climbing steep hills and maintaining speeds of 100+ km/h.

- When accelerating from a complete stop I can sometimes here a rattle or pinging sound coming from under the hood. I have been told that this pinging is actually the fuel injector trying to send fuel to the engine but that it is not in sync for some reason. I am wondering if this may be a sign of what is causing my other symptoms.

To me it seems like the problem has less to do with shifting gears, and more to do with what happens when the car is in a particular gear. This seems to occur most frequently when the car is in 5th. The problem also occurs much less frequently when I have the car in sport mode, and less frequently still when I manually shift gears.


Any advise guidance would be greatly appreciated.

Thanks!
 

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I am having the same problem. The revs go down and I get a vibration. Did you find the problem? Weird no one responded? Isn't this what the forum is for?
 

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Shazam I have a 320i aswell and when the rpms dip I hear a loud rub then it goes up dips again and rubs. It may possibly be the torque converter which is a expensive fix.
 

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I saw on Youtube a video of the same problem and they found it was the knock sensor. I had a misfire code on 2 cylinders maybe thats why? also read it could be the MAF sensor.
 

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Discussion Starter #5
Thanks for the responses. About 2 months ago drove over a big rough patch in some road construction (at night; not marked; very annoying), blew my two passenger side tires which activated my airbag sensor deploying my two side airbags. Insurance company wrote the car off and now have an 05 325i sans rev issues (touch wood :)

To address a couple of the above comments -

I had the misfire problem as well. With my car the misfire issue made it drive worse but fixing it just better isolated the rev jumping issue. I replaced all spark plugs and coils twice during the time I had the rev jumping issue. I averaged about 60000kms/year with this car - the problem started at about 110 000 kms and persisted through to 270 000.

Torque converter was one of the possibilities I had narrowed down to as well.

I had this specific problem diagnosed in BMW service departments both in California and British Columbia. They both said issue was computer programming so had the car's computers reprogrammed - did not help anything. After this step failed, I had the Canadian BMW service centre spend a few hours trying other random fixes - again no help at all. The problem persisted for about 150 000 kms and did not ever affect the car's ability to drive; no error codes ever showed. I had various other mechanics look at it and I found that the one's who did not understand BMW's always said the transmission was failing. I never thought this was true because to me the car never had issues changing gears, the issue was what happened within a given gear.

Other things I replaced trying to narrow down/fix the rev jumping issue- belts, water pump, battery (could have been problem with lack of power)

Other possibilities that I narrowed down to - Oxygen Sensor, Exhaust Sensors, fuel pump (possibly just needing cleaning).

Hope this helps. Please post if anyone finds out what the real problem is - I'm still really curious.
 

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Hi, im new here and im having the exact same problems. My 2004 325i is doing the same, it is in for its 100k service at the moment
and they also believe it may be a transmision problem...
 

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I have also just had the tramsmission fluid changed during the major service, i will let u know
if it helped my reving issues.
 

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i am also having the same prob with my 01 325ci but it is not as dramatic as the one in the video if any one has a solution it would be much appreciated. im going to try changing the fuel filter to see if it has any effect.
 

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My cars still having revving dramas, it's when I'm trying to hold a constant speed, 50, 70, 90, or 110km/h. It fluctuates approx 400rpm in any transmission mode! When the speed is under 60km/h and the revs drop, I
also get what seems like a vibration!

I'm getting my transmission flushed out tomorrow, there hooking it up to a machine which cleans it out. Hopefully it may sort out my revving dramas!

Sorry I do have a video I took on my iPhone but I'm not sure how to upload it!!
 

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Hi all, better late than never!!
I had my transmission serviced today, they hooked it up to the machine which thoroughly flushes & cleans out ALL the old fluid.

As I drove it home there was NO fluctuating revs, none at all!! It certainly changed gears smoother & took off from a standing start a lot smoother also!!

I should mention that I did not get any service record with the vehicle when I bought it. In saying that it seems that there are a few other BMW owners with this problem!

Hope this helps out!

Dan
 

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No One Wants to Touch

Got a question Dan- Did this problem only occur under a load (while driving)?
Can't seem to make it happen on the rack.
Took my 2004 325i to 3 reputable mechanic shops. All 3 had different ideas about the problem. The delema is that there isn't any fail light coming on so no one knows where to look. One place said it was a drive train problem. Another said it was a fuel pump (150000 mile extended factory warrantee) problem. The third place said it seems that it's somewhere before my transmission. either a computer problem, fuel, air, circuit, sensor, other problem. They ALL didn't want to just guess and start replacing random parts. Seems like the car is hunting between gears. Hear a rumbling from right rear at slow speed like the car is shifting too soon between gears. Very noticable when steady pressure on the gas pedal at almost any speed. VERY noticeable on long grades or hills. RPM dips 500 then goes back 500. I may try having the trans fluid replaced just for laughs. hahaha NOT
 

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By the way, the quote from two places to replace the fuel pump was $6,500 because you have to replace the whole fuel tank! Fuel pump is located inside the tank and is inaccessible.
BMW knows this is a problem and instead of doing a factory recall, they extended the fuel pump warrantee to 150,000 miles or 10 years.
Shame on BMW!
 

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They didn't extend the warranty they came with that from new. The fuel pump issue does suck. I got rid of the M56 I had before it went.
 

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Under load at speed sounds like a fuel pump problem to me, since the engine needs more fuel under those conditions.
Have the dealer replace the tank/pump, before your warranty runs out.
 

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Xxx

Iszlszx - Isn't the fuel pump dumb? I mean doesn't it work harder or or less by getting signals from a computer or carburator telling it to give the amount of fuel???
I'm passed warrantee or obviously I would have taken it to a dealer :(
 

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Got a question Dan- Did this problem only occur under a load (while driving)?
Can't seem to make it happen on the rack.
Took my 2004 325i to 3 reputable mechanic shops. All 3 had different ideas about the problem. The delema is that there isn't any fail light coming on so no one knows where to look. One place said it was a drive train problem. Another said it was a fuel pump (150000 mile extended factory warrantee) problem. The third place said it seems that it's somewhere before my transmission. either a computer problem, fuel, air, circuit, sensor, other problem. They ALL didn't want to just guess and start replacing random parts. Seems like the car is hunting between gears. Hear a rumbling from right rear at slow speed like the car is shifting too soon between gears. Very noticable when steady pressure on the gas pedal at almost any speed. VERY noticeable on long grades or hills. RPM dips 500 then goes back 500. I may try having the trans fluid replaced just for laughs. hahaha NOT
Mine does the same, rpms drop under slow steady acceleration. on flat terrain the little torque the 325 makes is enough to accelerate from there. There is also a humming/deep noise developing the lower the rpms go. Not sure if that's just the exhaust sound with the load at low rpm or coming from the drivetrain.
Keeping a steady speed uphill 40-50mph it will sometimes do that rpm dip you guys are reporting, loud vibration and slight hydraulic whine/scrape included. Only for a split sec though.

Bet it's trans related, converter is my guess.

If I drive it in manual mode in 5th the issue happens way less often, guess the programming allows more converter slip to begin with? Have you guys tried that?
I'm taking mine to a trans shop this week. Hope it's not too bad but I guess this one's gonna be expensive...
 
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