So I was driving my m3 today for about an hour and then all of a sudden the car goes into "limp mode", however there were no lights on the dash at all it would just redline at 4k. There were no codes at all. I am kind of lost.
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For some background, the fuel system has no sensors connected to the ECM; if there is a fueling problem, there will be no DTC code stored in the ECM. My guess is that your 4000 rpm cutoff is either a fuel pump that has seen its useful service life diminish and is about to pack its bags, and/or it’s a fuel filter that can allow acceptable fuel pressure at low-ish rpms, but when asked to allow greater flow (due to greater rpm), it can’t because it’s partially clogged, hence fuel flow at higher rpms is restricted.
How I handle the fuel system on my own sled is that when the fuel pump nears 100,000 miles, I replace it without hesitating. This allows me to control the situation, meaning I can visit my mechanic on my schedule, and under my control, rather than the pump dictate to me when it’s 110 deg F outside, stuck on a highway shoulder and on the phone calling for a tow. At 30,000 miles, I replace the fuel filter as a matter of required maintenance. So, enough blathering from me. Do a bit of research, rent/borrow a fuel pressure gauge, and buy gloves that do not dissolve when gasoline makes contact with it! Oh yeah, be prepared to pay the “BMW tax” on parts! 😆 🤣 -
Thanks for he info, but it ended up being a o2 sensor that melted onto the headers, it blew the fuse in the 5 fuse box in the dme box.Comment
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