(Fixed )2004 BMW Z4 E85 Cold Start Problem

2004 BMW Z4 E85 Cold Start Problem, what is the reason? how to solved? BMW ICOM interface under 199Euro can be very helpful.


Car model and year:

04 BMW 4 E85 with 23,800 miles bought used in 07 with 15K miles.
No service other than oil changes.



when car is cold and upon start after about 20 seconds engine has major skip and may continue to run for another 15 to 20 seconds and then will often cut off. After 2 or 3 more cycles of starting , running engine for 10 to 15 seconds the engine will then continue to run fine and then throughout the day no starting problems will be experienced.


Occasionally in one of those +/- 5 starting cycles engine will start and run but with very rough idle ( pressing gas pedal does not change RPMs) requiring that I perform a manual throttle reset that will often result in the next start as normal with no unwanted engine shut offs.


Suggestion 1:

  1. Have you checked the battery voltage? It’s very unusual to have an ECU, coding or even a mechanical issue at this mileage but if the battery is low all vehicle settings, memories and ECUs will go hay wire.

Result: I checked battery voltage this morning. 12.23 cold.

Ran battery charger for about an hour and charger indicated full charge but showed only 12.7.

Used another vehicle to jump and with jump vehicle running Z4 battery still showing 12.7.

Upon start same results of requiring throttle reset and 4 restarts until it ran without shutting off.


Suggestion 2:

If the battery/alternator power supply are sufficient, I would check the electrical throttle valve next. You can read more on this here:


and here:


Note that even the gas pedal position plays a role in initial calculations so make sure nothing is stuck there.


You most likely have the DME problem in this case as you have DME specific codes. All the lights and other problems including the throttle should resolve once the DME software is reflashed (excluding the seat belt tensioner which will require part purchase either new or from eBay). To update the DME software you will need to install Winkfp the flashing software which is part of the BMW standard tools. You will also need a connection to the car. The guy in the other forum that reflashed his own DME used the D-can cable that he purchased online and connected his laptop to his OBD port. The software and cable can be both acquired from BMW geeks here:

https://www.bimmergeeks.net/downloads  and here https://www.bimmergeeks.net/cables

Although he was successful in his task DMEs are notorious for requiring long time to update, flash or code which creates a higher risk of error occurring due to disconnection, low battery voltage and other causes. When errors occur during firmware installation there is a big risk of the DME becoming non responsive and you lose the ability for further trials to reupload the software or use the DME again (aka turning into a brick).
Therefore it has been advised that during DME software procedures the following must be met:
1- The vehicle must be connected to a charger of specific parameters and quality to provide a Continous (non pulsatile) charge with equals to or more than 90 amps during the entire procedure
2- The communication to the vehicle has to be done using a BMW ICOM device as used by the dealer. These are now sold online for about $200 range.

Some people elect to take the risk and attempt the more affordable route. Many succeed but some get in trouble.

After you install Winkfp you have to update the program with the Z4 most current software. This can be easily done using bmw coding tool and sp Daten files. All available through the link above.
Winkfp and ECU programming require some learning but there are many material on YouTube and BMW forums (e.g bmwcoding) that explain how to and help with software installation and computer settings.

If you find this process overwhelming you can always get the software updated at the dealer. Your indie probably has it too as he owns several BMWs. Otherwise BMWgeeks and other coders offer remote coding. On the BMWcoding website there are ads for local coding services by state as well. Good luck!


Finally solved:

Since my last post where I began to pursue

1) reprogramming of the DME by local tech or

2) purchase of the service from DME repair companies.


As I researched I selected Module Experts in Jacksonville FL.

With a lower price of $240 to repair and reprogram (I thought) I sent my DME to them. Also, based on verbal discussion of my trouble codes and including their web site indicating they could reprogram DMEs for BMW and Mercedes, etc. I contracted with them .Additionally, they did not require the EWS.


Shortly after they received my DME I received a call and the sales person indicating I had a short in the DME requiring replacement. Ouch! So after I agreed to another $688 they returned a re manufactured DME. After install of re man DME it performed just like my original DME. I experienced the same cold start symptoms, similar check sum, ram check, failures, and throttle error codes, etc.


I later determined they reloaded the same code from my original DME to the re manufactured supplied unit. At first the sales person was resistant to issue a credit for the re man DME claiming my original DME with the short remained the reason for my cold start problem. But after discussion with the senior tech where he stated “ we do not reprogram DMEs” and discussion with a manger, Darrel, he agreed to a refund after I returned the re man DME. In hindsight a poor decision on my part that resulted in $240 loss and continued Z4 down time.


After review of my problem with RPM and ECU doctors I selected RPM Motorsports, Canada to do the work on my original DME.


I received and installed the reprogrammed DME on Tuesday 3/26 and installed the EWS and DME.


Upon first crank same presentation of cold start issues. Did a manual throttle rest and with second crank it started OK (YEA!), although it seemed to run rough. Ran a code check and saw a host of new codes, but none of the RAM check failures and throttle codes.


New codes presented:

2786 Throttle valve potentionmeter 1

2787 Throttle valve potentionmeter 2

2807 Pedal position sensor

27Bd Exhaust Camshaft activation

2797 Idle speed control valve open

2796 Idle speed control valve closed

27C4 Main relay


Cleared codes.


Started ok but Z4 was presenting what seemed like misfire.

Read codes this time:


None of the above but just:

27AA Fuel Injector Cylinder 2


2746 Misfire Cylinder 2


Added some Fuel injector cleaner and ran for 10 miles or so but misfire remained.


So thinking now I have a bad injector on Cyl 2 from possibly the car sitting too long.


Also, I have restarted on multiple successive mornings with outside temp of high 20s and low 30 s and it started OK. After clearing codes and reread I saw again:


27AA Fuel Injector Cylinder 2


2746 Misfire Cylinder 2


So the saga seems to be coming to a close with cost of $530 and the reprogramming of the DME by a company (RPM ) with the expertise to fix it!


Source: https://www.bimmerforums.com/forum/showthread.php?2388104-2004-Z4-E85-Cold-Start-Problem


Edit by Laurance



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