Intermittent Throttle/Accelerator and Head Unit issue

[Andy Tate]

Hey fellow Z4 enthusiasts,

I'm experiencing a rather frustrating and intermittent issue with my 2003 3.0 E85 Z4, and I'm hoping someone here can provide some guidance or share similar experiences. The problem I'm facing is that both the car's head unit and accelerator pedal stop working intermittently, but then start working again after a few hours or days. I've tried the usual troubleshooting steps of turning the car off and on again, but it doesn't make any difference.

To investigate further, I decided to read the car with a scanner, and it provided me with the following 4 error codes:

2806 DME: Cruise control - time limit of data transmission reached.
27B5 DME: Inlet Camshaft - Activation.
MAF sensor issue (I'm already planning to replace this).
279C DME: Thermostat - Map Cooling Activation.
Based on my research and the symptoms I'm experiencing, I suspect the issue could be related to a faulty voltage regulator in the alternator. I've had a few other strange electronic issues in the past, and despite having a new battery that I recharge regularly, these problems persist. Therefore, I'm planning to order a new MAF, alternator, and potentially a throttle body and camshaft position sensor.

However, before I go ahead with these replacements, I wanted to reach out to this knowledgeable community to see if anyone has encountered a similar problem or has any additional suggestions for the list of parts to consider. I appreciate any input or insights you can provide.

One thing worth mentioning is that my Z4 is an automatic, and when I put it into gear, it moves backward and forward without any issues using idle revs. However, when I try to accelerate by flooring the pedal, there is no change in the RPM. This leads me to believe that the transmission itself is fine. It's also unusual that whenever the accelerator isn't working neither is the head unit and when the head unit is working the accelerator is fine.

I'm eager to get this issue resolved and continue enjoying my Z4 to the fullest. Thank you all in advance for your help!

Best regards,
Andy

 

[Andy Tate]

Hey everyone,

I wanted to provide an update on the issue I've been experiencing with my Z4. After some further investigation, I discovered a sensor under the engine cover that was unplugged. Upon plugging it back in, all the error codes I previously mentioned have been cleared, except for the MAF sensor issue.

Based on this finding, I believe that the unplugged sensor was the camshaft position sensor, which explains some of the symptoms I was encountering. Therefore, I no longer believe there is an issue with the throttle or camshaft.

Taking all of this into account, I have decided to proceed with purchasing a new MAF sensor and a new alternator. However, I have a question regarding the alternator replacement: Do I need to purchase new bearings separately, or do they come included with the new alternator?

I appreciate any advice or information you can provide regarding this matter.

Thank you for your support!

 

[enuff_zed]

and a new alternator. However, I have a question regarding the alternator replacement: Do I need to purchase new bearings separately, or do they come included with the new alternator?

I appreciate any advice or information you can provide regarding this matter.

I would consider simply changing the diode/brush pack on the rear of the alternator. It can be done in situ.
Check which alternator you have and you should be able to find the replacement pack for around £30 if memory serves me right.

 

[j3nks79]

Before buying replacement parts. Have you tested the alternator to see what voltage it’s putting out?
Also have you checked for split pipes around the intake?

 

[Andy Tate]

Before buying replacement parts. Have you tested the alternator to see what voltage it’s putting out?
Also have you checked for split pipes around the intake?

About 1-2 months ago, I had the split pipe fixed, and during that process, I noticed that the MAF (Mass Air Flow) sensor needed to be replaced because some brittle plastic parts snapped while removing the pipes. To prevent any potential issues with loose plastic entering the intake or throttle body, I decided to remove all the plastic myself. Regarding the alternator, I haven't tested it yet, but I'm experiencing the typical symptoms of a faulty regulator. Occasionally, my dashboard flickers, and I get random warning lights that usually go away when I turn the car on and off. However, this time, the warning lights persist. I recently tested the battery, and it showed an 80% charge, which is good since it was recently replaced and has full capacity.

and a new alternator. However, I have a question regarding the alternator replacement: Do I need to purchase new bearings separately, or do they come included with the new alternator?

I appreciate any advice or information you can provide regarding this matter.

I would consider simply changing the diode/brush pack on the rear of the alternator. It can be done in situ.
Check which alternator you have and you should be able to find the replacement pack for around £30 if memory serves me right.

I'm not entirely sure, but I believe the alternator in my car is the original equipment manufacturer (OEM) one. Given that my car is 20 years old, it might be worth considering replacing the entire alternator instead of just the voltage regulator. The approximate cost of an alternator is around £150. What do you think? Is it more practical to replace the whole unit rather than just the regulator?

 

[enuff_zed]

Before buying replacement parts. Have you tested the alternator to see what voltage it’s putting out?
Also have you checked for split pipes around the intake?

About 1-2 months ago, I had the split pipe fixed, and during that process, I noticed that the MAF (Mass Air Flow) sensor needed to be replaced because some brittle plastic parts snapped while removing the pipes. To prevent any potential issues with loose plastic entering the intake or throttle body, I decided to remove all the plastic myself. Regarding the alternator, I haven't tested it yet, but I'm experiencing the typical symptoms of a faulty regulator. Occasionally, my dashboard flickers, and I get random warning lights that usually go away when I turn the car on and off. However, this time, the warning lights persist. I recently tested the battery, and it showed an 80% charge, which is good since it was recently replaced and has full capacity.

and a new alternator. However, I have a question regarding the alternator replacement: Do I need to purchase new bearings separately, or do they come included with the new alternator?

I appreciate any advice or information you can provide regarding this matter.

I would consider simply changing the diode/brush pack on the rear of the alternator. It can be done in situ.
Check which alternator you have and you should be able to find the replacement pack for around £30 if memory serves me right.

I'm not entirely sure, but I believe the alternator in my car is the original equipment manufacturer (OEM) one. Given that my car is 20 years old, it might be worth considering replacing the entire alternator instead of just the voltage regulator. The approximate cost of an alternator is around £150. What do you think? Is it more practical to replace the whole unit rather than just the regulator?

Up to you really, but I fitted a new regulator pack on my wife's 2.5i on 103k and it sorted the problems.