BMW Z3 Power Loss: Throttle Valve or Something Else?

Hey there! I had a similar issue with my 2000 BMW Z4 last summer. I have some experience working on cars, but this was something I needed professional help with. The symptoms you're describing sound exactly like what I experienced. My car also went into limp mode, had poor throttle response, and the check engine light was on. Turned out it was a faulty accelerator pedal module. The electronics inside were shot, which was causing all those problems. Took it to my regular workshop and they diagnosed it pretty quickly. They replaced the entire accelerator pedal module, cost me around 265 Euro including labor. Car's been running perfectly since then. What's your current mileage and have you had any other warning lights or error codes? That info would help determine if you're dealing with the same issue. Also, have you noticed if the problem is worse when the engine is cold or warm?

Thanks for sharing your experience! I'm sitting at 199451 KM and just had my service done last month. The issue actually seems worse when the engine is warm, which is different from what you described. I haven't pulled the error codes yet, but I'm planning to get that done tomorrow. The accelerator pedal module is definitely something I'll have them check out, the symptoms do sound pretty similar to my case. I used to do basic maintenance myself, but this seems like it might be beyond my comfort zone. Especially since it's acting up so unpredictably. Appreciate the tip about the repair costs too, helps to know what I might be looking at if it turns out to be the same issue!

Hey again! Thanks for the follow-up. Since you mentioned it's worse when the engine's warm, that actually makes me think we might be dealing with different issues here. In my case, the accelerator pedal module problems were pretty consistent regardless of engine temperature. Just remembered, before I got mine diagnosed properly, I tried cleaning the throttle body thinking that might help (totally wasted my time there!). In your case, with those symptoms getting worse with heat, I'd bet you're looking at an electronic throttle control issue rather than the pedal module I had. My mechanic actually showed me that these BMWs from our era have a pretty complex electronic throttle system. Have you noticed any unusual noises when you turn the key but before starting the engine? In these cars, you should hear the throttle body doing a self-check, kind of a whirring sound. If that's missing or sounds weird, it could point to your throttle body being the culprit after all. Just keep me posted on what those error codes show up. Really curious to know what's causing this in your case. These old Beemers can be tricky sometimes, but they're worth fixing right!

Thanks for that detailed insight! After reading what you've shared, I'm definitely leaning more towards it being the throttle body. You know what's interesting, now that you mention it, I've noticed that whirring sound has been different lately. It's more like a stuttering noise than the smooth whir it used to make. I finally got those error codes pulled today, got P1511 and P1512, which apparently are related to the throttle control system. That pretty much confirms what you were suggesting about the electronic throttle control being the likely culprit. Not what I was hoping for, but at least now I know what I'm dealing with. Looks like I'll be making that workshop appointment sooner rather than later. My car's definitely worth fixing right, she's been such a reliable ride up until now, and I'd like to keep her running smoothly for years to come. Really appreciate you taking the time to share your experience and knowledge. It's helped me narrow down the problem and know what to expect when I take it in!