BMW Z3 Losing Power? MPG Drop Points to MAP Sensor Issue

I had nearly identical issues with my 2003 BMW Z4 last summer. The symptoms were spot on, poor acceleration, drinking fuel like crazy, and that dreaded check engine light. Turned out to be a major vacuum leak caused by cracked intake boots and worn gaskets. The rubber had deteriorated badly over time. The fix wasn't quick, my mechanic had to replace several components: intake boots, valve cover gasket, and the vacuum lines. It was pretty serious since the engine wasn't getting proper air-fuel mixture, which could've led to more expensive repairs if left unchecked. My advice? Get a proper vacuum leak test done. In my case, the manifold pressure sensor readings were off because of the vacuum leaks, not because of a faulty sensor. Don't just replace parts without confirming the real issue first. You'll want this fixed soon, mine got worse quickly and started affecting engine performance even more. Just keep in mind that old BMW rubber parts tend to crack and fail around this age.

Hey, thanks for sharing your experience! That's exactly what I needed to hear. I'm dealing with the same mess right now and it's driving me crazy. It's good to know I'm not alone with these issues. Just curious, do you remember roughly how much you ended up paying for all those repairs? Also, has everything been running smoothly since the fix, or have you noticed any other problems popping up? I want to make sure I budget properly for this and know what I might be getting into.

Hey there! Just wanted to update you on what happened after my last post. So I finally got it all sorted, turned out my situation was a bit different from what I initially thought. The mechanic found a significant vacuum leak that needed fixing, which set me back 235 €. But here's the good news, they also discovered and replaced the faulty manifold pressure sensor while they were at it, and honestly, it's made a world of difference! The car's running like a dream now, no more sluggish acceleration, fuel consumption is back to normal, and that annoying check engine light has finally gone off. It's been about six months since the repair, and I haven't had a single issue pop up. My Z4 feels like it's got its mojo back! Just a heads up though, if you're getting it checked out, make sure they do a thorough vacuum leak test. These old BMWs can be tricky, and sometimes what seems like one problem can be hiding another. Tell them to check everything while they're in there, it'll save you money in the long run. Trust me on this one!

Thanks a lot for the detailed follow-up! I actually took my Z3 to a different mechanic yesterday, and boy, what an eye-opener! They did a complete diagnostic check and found multiple issues. The vacuum leak was definitely there, just like you mentioned. They also spotted a worn-out oxygen sensor that needed replacing. The whole job cost me about 400 bucks, which wasn't as bad as I feared. Had to wait a few hours while they fixed everything, but it was worth it. The car's running much better now, that sluggish feeling is gone, and I can already tell it's using less fuel. Funny thing is, while I was at the shop, the mechanic showed me the old parts. Those rubber components were in terrible shape! Makes me wonder why my previous mechanic missed something so obvious. Really glad I asked for advice here and found a better shop. Guess sometimes you need a second opinion to get things right. Thanks again for pointing me in the right direction!