Engine trouble - "Tach Jump" causing power loss - ANY IDEAS?

[Night1]

Has anyone else experienced this or something similar?

About 2 weeks ago, my car started losing power under acceleration. Normally (no matter what gear I’m in) the car starts accelerating as soon as I push the gas pedal. Now, there is a slight delay between pushing the gas pedal and actual acceleration.

When you watch the tach under acceleration, instead of smoothly winding up, it jumps up for a second, and then comes back down to where it started the “jump” and finally begins to progressively climb. This “tach jump” happens during the delay in acceleration. After this short “tach jump” is over with, power finally comes on and pulls strong.

To further illustrate, instead of the tach progressing smoothly from 500 to 1000, 1500, 2000, 2500, 3000, etc., it goes more like 500, 1000, 3000 (“the jump”), 2500, 1000, 1500, 2000, 2500, 3000, etc.

There are no engine codes. My car has about 14,500 miles on it. The only mod is a Riss Racing air intake that was installed about 3 months ago. My car has a manual transmission. The car idles fine.

The friends I have discussed this problem with think it’s a transmission issue. My BMW service center is currently claiming that my transmission is fine and that the problem is due to my air intake. I have spoken to Daniel at Riss Racing and he says he is not aware of any similar issues with vehicles equipped with their intakes. I think that if my problem were due to the intake that it would've started right after the intake was installed.

Either way, my BMW center is requiring me to remove my intake and replace it with the stock one before they will continue their evaluation.

Any ideas? :iono:

[Dave]

i would def. put your stock intake back ... let the warranty figure it out

[coco_m3]

Remove intake, go in for service.

[Dangerlucas]

Put the stock intake back in to satisfy their request, but there is no way the RR intake would cause something like this. I'd guess that your clutch might be slipping.

[jeremyc74]

The only way the tach can jump on a car with a manual transmission is if the clutch is slipping. As long as the clutch is properly engaged the engine RPM is directly dependent on the speed the vehicle is travelling.

Is the car lurching around while this is going on?

I'd certainly take the intake off to prevent them from having anything to blame, but I really can't see any way it has anything to do with this.

What happens when you take the car out and do a long pull in 3rd or 4th gear from low RPM? If it's the clutch slipping you should be able to duplicate it like that.

[Night1]

Originally Posted by jeremyc74

The only way the tach can jump on a car with a manual transmission is if the clutch is slipping. As long as the clutch is properly engaged the engine RPM is directly dependent on the speed the vehicle is travelling.

Is the car lurching around while this is going on?

I'd certainly take the intake off to prevent them from having anything to blame, but I really can't see any way it has anything to do with this.

What happens when you take the car out and do a long pull in 3rd or 4th gear from low RPM? If it's the clutch slipping you should be able to duplicate it like that.

There is no lurching while this happens. The power smoothly comes on, fades away (during the "tach jump"), and then smoothly comes back in and begins acceleration. It feels like a slip. The power delivery is almost like severe turbo lag.

The problem is most apparent from the higher gears, such as 3rd and 4th. From low rpm in those gears, the tach still jumps as described.

[jeremyc74]

Originally Posted by Night1

There is no lurching while this happens. The power smoothly comes on, fades away (during the "tach jump"), and then smoothly comes back in and begins acceleration. It feels like a slip. The power delivery is almost like severe turbo lag.

The problem is most apparent from the higher gears, such as 3rd and 4th. From low rpm in those gears, the tach still jumps as described.

A disconnect between the tach and vehicle speed that's noticeable in the higher gears is almost certainly the clutch slipping. Take the tech for a ride and let him see it first hand.

One other question:

Does it do this all the time, or just after the car has been parked for a while? I'm wondering if you've got a leak from the slave cylinder that's getting on the clutch and allowing it to slip. It seems like I've heard of this happening before, but I'm not positive.

Let us know how it turns out. :w00t:

[ocinek]

The only possibilities are either your clutch is slipping, or tires are spinning.

[Night1]

Originally Posted by jeremyc74

A disconnect between the tach and vehicle speed that's noticeable in the higher gears is almost certainly the clutch slipping. Take the tech for a ride and let him see it first hand.

One other question:

Does it do this all the time, or just after the car has been parked for a while? I'm wondering if you've got a leak from the slave cylinder that's getting on the clutch and allowing it to slip. It seems like I've heard of this happening before, but I'm not positive.

Let us know how it turns out. :w00t:

I did take the head tech and another technician for a ride. This issue happens all the time, regardless of whether the car has been parked for a while. For instance, I drove the car for an hour before I dropped it off at service and I was still able to replicate the problem in front of the techs.

I agree that this is probably caused by the clutch slipping, that makes sense.

Originally Posted by ocinek

The only possibilities are either your clutch is slipping, or tires are spinning.

There is no tire spin at all (especially at higher speeds and gears) so it is probably the clutch.

Thank you all for your advice! :headbang: Now if I only I can convince BMW.......

[Chewyjr15]

a new clutch already, id say if bwm wont cover it which they should put in a spec clutch or somethign beefier.

[imdanomite]

i'd suspect a boost leak somewhere in the intake system. MAF on BMWs are known to be very sensitive and could also be a problem.

[Reach]

Are these symptoms entirely outside of what happens with an HPFP failing? I am not familiar, just asking / throwing out another possibility.

[Noize]

If its a manual, that's definitely a slipping clutch. It will happen where torque rises abruptly, so the 3000rpm makes sense.

[imdanomite]

the HPP would throw a engine malfunction message. or a excessive crank symptom

[Night1]

Originally Posted by imdanomite

i'd suspect a boost leak somewhere in the intake system. MAF on BMWs are known to be very sensitive and could also be a problem.

I will suggest this possibility to them

Originally Posted by Noize

If its a manual, that's definitely a slipping clutch. It will happen where torque rises abruptly, so the 3000rpm makes sense.

The majority agrees so far....

Originally Posted by imdanomite

the HPP would throw a engine malfunction message. or a excessive crank symptom

You're probably right, and there have been no codes as of yet.

You know, the unfortunate thing is I have a whole trunk full of Riss Racing products that I was about to install and a Vishnu tune planned but this engine malfunction has really pissed all over those plans. I'm beginning to not even excited about modding my car any more. They had better get this fixed while I still have the bug!!

[Chewyjr15]

like others have said you wanna mod be ready to pay for repair bills should they arise. A clutch though is usually replaced whenever doing a high hp engine build. Have you abused it? Is this you first manual? Any hard launches?

[AussieRacer]

Apart from watching the tacho move, do you actually hear the engine rev higher and then drop?

All this talk of clutch slip cause the tacho needle moves, doesn't mean anything unless the engine is actually matching what the tacho is saying.

I've seen people rev the crap out of a car wondering why they can't get it to rev more the 5000rpm, only to discover there was a problem with the tacho/sensor, not the engine.

[123D-M]

This sounds exactly like the problem I have been having. Clutch slips immediately after an up-change. Car hesitates or sometimes jerks a bit while the clutch is struggling to grip, then it goes as normal.

FYI. I've already had my clutch and gearbox replaced as when BMW opened it up they discovered that oil was leaking into the clutch. This was causing the slip when you change gear and it eventually caused my clutch to be completely fried. Unfortunately for me, even after having everything replaced it has started doing it again so it is going back to the dealer after xmas.

Anyway, the point is, that slip after a gearchange is almost certainly caused by oil in the clutch. PM me if you want further details. I'm 99% sure that the clutch mechanism would be the same between a 123d and a 135i.

[Night1]

Originally Posted by Chewyjr15

like others have said you wanna mod be ready to pay for repair bills should they arise. A clutch though is usually replaced whenever doing a high hp engine build. Have you abused it? Is this you first manual? Any hard launches?

Spirited driving but no abuse. I've been driving manuals for 13 years.

Originally Posted by AussieRacer

Apart from watching the tacho move, do you actually hear the engine rev higher and then drop?

All this talk of clutch slip cause the tacho needle moves, doesn't mean anything unless the engine is actually matching what the tacho is saying.

I've seen people rev the crap out of a car wondering why they can't get it to rev more the 5000rpm, only to discover there was a problem with the tacho/sensor, not the engine.

You can hear the engine rev along with the tach.

Originally Posted by 123D-M

This sounds exactly like the problem I have been having. Clutch slips immediately after an up-change. Car hesitates or sometimes jerks a bit while the clutch is struggling to grip, then it goes as normal.

FYI. I've already had my clutch and gearbox replaced as when BMW opened it up they discovered that oil was leaking into the clutch. This was causing the slip when you change gear and it eventually caused my clutch to be completely fried. Unfortunately for me, even after having everything replaced it has started doing it again so it is going back to the dealer after xmas.

Anyway, the point is, that slip after a gearchange is almost certainly caused by oil in the clutch. PM me if you want further details. I'm 99% sure that the clutch mechanism would be the same between a 123d and a 135i.

Very interesting. I just sent you a PM and I'm going to mention this possibility to the tech today.

[BlackjackMulligan]

When you took the tech out to experience the problem, did he make any suggestions as to what he thought it was?

[Night1]

Originally Posted by BlackjackMulligan

When you took the tech out to experience the problem, did he make any suggestions as to what he thought it was?

No, I asked both techs several times during the drive what they thought and they said they didn't know but would check it out.

Honestly, I think it's their policy not to guess or think aloud before they've had a chance to evaluate it.

OR (worse case scenario) maybe they just don't know what they're doing! :eyebulge:

[123D-M]

Originally Posted by Night1

No, I asked both techs several times during the drive what they thought and they said they didn't know but would check it out.

Honestly, I think it's their policy not to guess or think aloud before they've had a chance to evaluate it.

OR (worse case scenario) maybe they just don't know what they're doing! :eyebulge:

Sigh. I know they must hate customers that self-diagnose their problems like us but still, sometimes I get annoyed that the techs don't listen carefully when you describe the problem. The worst thing is when they give it back and say there is nothing wrong with it.

I've had quite a lot of problems with my car so I kept a diary of every single little thing that went wrong. Then I had it well documented and could tell them exactly how many times things had happened. My iDrive computer was replaced because something went wrong with the bluetooth and they were unable to reprogram it.