Sudden brief power loss

[ZEDonist UK]

Hi all,

Time to ask for help:

I have a 2000 3.0 Z3.

When driving, any speed and any throttle position the car suddenly loses power and almost immediately gets it back again. Its especially noticeable when you’re giving it beans.
It’s as though you quickly stab the breaks before immediately hitting the accelerator again.
The engine revs don’t appear to drop.

I have replaced the vacuum lines
Replaced intake boots and small tubes from F connector
DISA valve rebuilt and seal replaced
Throttle body removed and cleaned

I have an Autel scanner and it shows no fault codes.

The car idles fine.

I can’t hear or identify any air leaks.

Im sure the VANOS needs rebuilding as the car lacks power until higher revs - it’s a bit like turbo lag.

I’m not entirely sure what could cause this so not sure where to start. Hence asking for guidance.

Thanks all

 

[t-tony]

If it's a "fly by wire" throttle (which I think it should be on a 2000 model) it's possible an issue with the throttle pedal itself although you might expect a code to throw up. May be worth removing the pedal and applying contact cleaner on the electrical connections.

Tony.

 

[NZ00Z3]

Do any dash warning lights flash when the power drop happens? The traction control or ABS lights maybe?

Are any warning lights on all the time?

Two modules can control the throttle. The DME and the ABS. Hence the questions about the ABS and traction as I'm guessing that your Autel scanner does not have BMW software, so can't read the ABD trouble codes?

Oh, and you have to use the 20 pin port under the bonnet/hood if you want to read all the Cars modules. The OBD2 port only connects to the DME and EGS.

There are several options for scanners with BMW software:

• INPA on a windows laptop: https://www.bimmerforums.com/forum/...tions-Experiences-Discussions-Experimentation
• Foxwell NT530 with BMW software.
• Creator C110
• Creator C310+

If there are no trouble codes in the DME or ABS, then we are looking at engine diagnostics or other things like ignition switches.

 

[ZEDonist UK]

@NZ00Z3

No warning lights come on

No permanent warning lights

I am using the 20 pin port

I have purchased the BMW-service package from Autel so as far as I am aware I have pretty full access.

I can specifically choose to scan each module.
Interestingly I have the following codes. These codes didn’t show up when doing a global/auto scan (a function which works well on a 2014 Vauxhall).

Module:
“Engine-DME Motor Electronics MS43”
Faults:
“12 DME: Signal, camshaft sensor, exhaust”

“78 DME: Plausability, accelerator and brake pedals”

“27 DME: plausability, signal, brake light switch/brake-light test switch”

Module:
“ABS-DSC Stability Control MK60”
Fault:
“5E40 ABS-DSC: steering angle implausible”

Unable to scan modules:
“ABS-DSC MK20 automatic stability control”
and
“ABS-DSC Stability Control DSC3”


I have cleared all fault codes. It’s getting dark, it’s cold and wet so I’ve gone to hide inside again.
I’ll go for a spin tomorrow then re-scan and see what we’ve got.

 

[2bmws]

Does the lights come up on dash like it cuts out for a brief second then comes back to life, if so it's the crank sensor

 

[ZEDonist UK]

Nope
No warning lights of any description

 

[NZ00Z3]

OK the trouble codes make sense.

78 (hex), 120 (Dec), Plausibility Pedal Sensor or TPS. When the DME does not know where the throttle body position or the pedal position sensor is, it just cuts the power to limp mode. Usually the engine light comes on and you have to restart the engine to clear the limp mode.

27 (Hex), 39 (Dec) Brake Light Switch or Brake Light Test Switch. This means you need a new brake switch. Cruise control will not function. It will bring up the "Cog of Death" light on the dash if you have an auto transmission.

Clear the codes and se what comes back after the next power loss event.

For the ABS fault code, you may have to recalibrate the steering angle sensor. Once again, clear it and see if it comes back.