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#1
09-28-2025, 04:45 AM
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2003 E320 W211 high rpm misfires and low power
Hello everyone, I own a 2003 W211 E320 M112.949 vehicle. When I drive my car and exceed 4-5k rpm, the car goes into protection mode and cuts off the ignition of some of the cylinders (p0304, p0301, p0305 p,0300). I replaced 12 spark plugs, replaced the oxygen sensor, replaced most of the ignition cables, replaced the coils, I suspected a clogged catalytic converter, so I bought and installed new catalytic converters, but the problem persists. When I discussed this issue with ChatGPT, it mentioned a faulty crankshaft position sensor or weak alternator or battery. I'm seeking help from those who have experienced a similar issue and managed to resolve it. Thank you.(i checked the fuel system there is no problem)
after catalytic converter and spark plug replacement and tried without airfilter I revved it up to 5-6k rpm about 10 times and only got a misfire error once, but at high revs, it feels like something is holding the car back, the power decreases, and it shifts gears late, meaning the car has more power at low and mid-range revs. 
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#3
09-29-2025, 01:06 PM
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my experience with crank sensors and those m112/113 motors is that they work or they don't. no weird running problems. stalls when hot, cools off, start again or just plain won't start.
expensive dartboard-cats and all. IF it needed cats and IF the old ones broke apart, it MAY be clogging the exhaust.
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#4
09-29-2025, 01:12 PM
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other things came to mind. had 1 m112 that ran bad, forget the details-been 15 yrs ago.
low fuel pressure from bad regulator on the fuel filter or clogged filter. numerous vacuum leaks near the mass meter and the mass meter was running lean. in those days, mass meters were dropping like flies and got done alot. the other things i, nor anyone else in the shop, had to do to get those running right. smoke test and fuel pressure test it.
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#5
09-30-2025, 07:47 PM
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Sounds like an air mass meter to me.
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#6
10-01-2025, 04:37 AM
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My car has 330k miles on it. I replaced the crankshaft position sensor, and there's some improvement at idle. At high RPMs, the car feels weak and shifts gears slowly. I'm no longer getting a misfire error in gasoline mode; it only happens on LPG. I measured the fuel pressure, and it's normal. I did a smoke test and didn't notice anything. Could a faulty EGR valve make a 224hp car feel like it's only 150hp? still it feels like something is holding the car back at high rpm
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