Rough and oscillating idling - Code P1633 and P1632

[mMark]

Hi all,

In one week from now I am planning to take the Z4 (3.0 M54 from 2003) on vacation. However, recently it started showing some issues that I have not been able to resolve yet, so I really could use your help

When I started the Z4 recently it didn't run well: a very rough idle with oscillating revving, very similar to what a fellow forum member experienced:
viewtopic.php?p=1736706&hilit=p1633#p1736706
And with a nice video that he uploaded:
https://thevisioneers.io/z4/

This is the exact same issue that I am experiencing. Reading the error codes both P1633 Throtthe Valve Adaption; Limp Home Position and P1675 came up. Searching the forum, it looked like I have a faulty throttle body so I removed it for inspection. Shaking the throttle body by hand, I heard a soft rattling noise on the inside, which would be a broking plastic gear according to Scooba_Steve in this topic. So I ordered a new throttle body (Meat & Doria 89256).

However, after replacing the throttle body the issue is still there
I am still getting the rough oscillating idle between 900 and 1200 rpm and pushing the pedal hardly does anything: it will stall and then move up to around 1300 rpm but still running quite rough. It is now showing code P1632 and P0102 with the yellow DSC, EML, engine and brake light on. I will spend some time later to search the internet.

What I have done so far:
- replace throttle body for a new Meat & Doria
- reset the throttle body (10/15 second on/off procedure and also by disconnecting the battery for 20 minutes)
- checked intake: no sign of ruptures etc
- disconnected Mass Air Flow (MAF) sensor
- cleaned the idle control valve

Any suggestions on what could be the issue here?
I was also looking for the Throttle Position Sensor, but so far couldn't find any information on where they are located? (in the gaspedal assembly and under the bonnet..?)

[enuff_zed]

Any mention of the DME?
Sounds similar to when mine died

[mMark]

Any mention of the DME?
Sounds similar to when mine died

Can you tell a bit more about the DME? I know it's the computer unit in the box underneath the bonnet, but can it be swapped easily with another unit..? What were the symptoms that you were experiencing? And what car do you have?

[Jack London]

Have you been having any electrical issues?
I had oscillating idle of various forms at different times. Similar error lights but no codes. With me it was my voltage regulator but the electrical issues were also there. Cutting out of music dimming of lights resetting hardware etc.

[mMark]

Just connected INPA to the car and read the error memory:
2786 Throttlebody potentiometer 1 - signal or value above the threshold
2787 Throttlebody potentiometer 2 - signal or value below the threshold
2796 Throttlebody: Adaptation values incorrect
Also some MAF / air inlet temperature errors (2783 and 278C), but that might also be related to the MAF sensor that I unplugged a few times.

[mMark]

Have you been having any electrical issues?
I had oscillating idle of various forms at different times. Similar error lights but no codes. With me it was my voltage regulator but the electrical issues were also there. Cutting out of music dimming of lights resetting hardware etc.

No, I haven't experienced any electrical issues. That all still works normally.

[smorris_12]

From memory you can use INPA to read the throttle pedal values. I'd do that to check it's not a failure of the pedal itself to start with.

[mMark]

From memory you can use INPA to read the throttle pedal values. I'd do that to check it's not a failure of the pedal itself to start with.

Great suggestion, thanks! I just plugged the computer to the car again and the pedal seems to work normally: the Fahrpedalwert (accelerator pedal value) nicely goes from 0% to close to 100% when pressing the accelerator pedal. Also the voltage of Pedalwertgeber 1 and 2 is increasing when the accelerator pedal is pressed. So unfortunately, the pedal sensors don't seem to be the issue...

I have reset the error codes in INPA and now only 2796 Throttle Valve Adaption failure comes up. It might be that one of the previous errors was related to the throttle body being disconnected during one of my test runs: this shows the exact same behavior as a connected throttle body.

Any other suggestions?

[smorris_12]

Three thoughts:

* Possibly a DOA replacement. It does happen

* Damaged wiring or connector (only really feasible if other work was carried out first.)

* Have you googled for other people's experiences of this error code in case it's an obscure and unrelated cause?

After that, since nuff_zee () pointed at the DME, I'd be onto that like a BOGOF deal at a brothel.

[enuff_zed]

Sorry for the slow reply. Abroad with crap signal.
The DME is easy to pull. Then do the usual Realoem check to find a compatible one.
It will need the VIN put in and the link to the EWS switching off.
Bigwinn is the guru

[mMark]

Thanks all for the responses and support, much appreciated!

I just ordered a second hand DME with key; according to Ruud van Vuuren (BMW Z3/Z4 dealer in Reeuwijk, NL, very friendly and helpful guy!) you can swap this easily if you have the ring antenna and the key of the "new" one. The one I bought is also for an E85 with M54 3.0 with manual transmission. Should I check numbers for compatibility or should this be ok?
That unit should arrive coming week. What exactly should I do with the VIN number? Is that done via INPA? And switching off the link to the EWS, does that mean you don't need to put the antenna+key of the "new" DME somewhere?

I am travelling to the UK next week for work so basically only have next weekend to fix the car. Hence, just ordered an extra throttle body just in case the new one is DOA (I can return the extra one anyways). Hopefully it will be up and running on time for my vacation!

[enuff_zed]

Thanks all for the responses and support, much appreciated!

I just ordered a second hand DME with key; according to Ruud van Vuuren (BMW Z3/Z4 dealer in Reeuwijk, NL, very friendly and helpful guy!) you can swap this easily if you have the ring antenna and the key of the "new" one. The one I bought is also for an E85 with M54 3.0 with manual transmission. Should I check numbers for compatibility or should this be ok?
That unit should arrive coming week. What exactly should I do with the VIN number? Is that done via INPA? And switching off the link to the EWS, does that mean you don't need to put the antenna+key of the "new" DME somewhere?

I am travelling to the UK next week for work so basically only have next weekend to fix the car. Hence, just ordered an extra throttle body just in case the new one is DOA (I can return the extra one anyways). Hopefully it will be up and running on time for my vacation!

Ah didn’t realise you weren’t UK.
I think even with another key you still need to get the DME and EWS talking. I’ve seen people change the whole lot with all the keys so I guess it may be possible??
Only way I’ve seen it done is as I described.
You need to put the new VIN into the DME. But then the car will turn over but not start as the DME checks with the EWS that all is good. The EWS still won’t like the new DME.
Simplest answer is to tell the DME not to ask for permission from the EWS.
Having trouble referencing Bigwinn from my phone.
Suggest you send him a PM

[mMark]

Thanks for the clarification! I have reached out to Bigwinn

Searching the forum I came across your topic, enuff_zed, where you described the issues that you were experiencing. Clearing the error memory with the engine running triggered me: I gave that a try and it worked for me as well! Also longer than 10 seconds: I drove around the parking lot and all seemed to function normally, apart from all the yellow dash lights. Throttle respons was also good. Turning the engine off and restarting it resulted in the rough idling again. I hope this confirms that the DME is the culprit.

[enuff_zed]

Thanks for the clarification! I have reached out to Bigwinn

Searching the forum I came across your topic, enuff_zed, where you described the issues that you were experiencing. Clearing the error memory with the engine running triggered me: I gave that a try and it worked for me as well! Also longer than 10 seconds: I drove around the parking lot and all seemed to function normally, apart from all the yellow dash lights. Throttle respons was also good. Turning the engine off and restarting it resulted in the rough idling again. I hope this confirms that the DME is the culprit.

Sounds like it. Hopefully Stuart can help further as I’m struggling with random signals until I get back off holiday

[mMark]

I am in contact with Stuart now, thanks!

I also have some question related to the DME / ECU swap specifically, so I decided to start a new topic on this. Link = below. Any feedback is more than welcome:
viewtopic.php?t=144012