Bmw hesitations and slight misfires when accelerating


i have a 2008 bmw 535xi. for a long time the car has been hesitating and slightly misfiring when accelerating. i have switch spark plugs and tested coils so its not that. i also replaced o2 sensor bank 1 sensor 1, map sensor(was covered in oil), fuel pressure sensor. the car is throwing codes p0420, p0430, p0133, c0300, p0001, p0171. freeze frame from cylinder 1 misfire shows shrtft1 was at 22 % positive.
longft1 was at 1.6% positive.
shrtft2 was 0.8% positive
longft2 was 2.4% negative
rpm was at 1000.
the fuel trims seem to stay in similar way at idle aswell with either shrtft1 at around %20 positive and longft1 lower closer to 0 or the other way around.
could this be a vacuum leak or bad catalytic converter? maybe bad injectors? i dont know help me out. thank you

Always start at the lowest number DTC.


Have you got the vin number or know which engine you have?
There’s various things to check depending on if it’s direct injection or not.

its direct injection i believe its e60 engine

If you’re thinking air leak they are not unknown for split breather hoses around the cam cover at the back and the one under the manifold, smoke test is really the best test as it can be very small and still cause issues, if you unplug the rail sensor it will default to a pre set if this cures it when you drive it’s to do with the high pressure supply, from memory there was a recall on either the hp pump or the pressure/temperature sensor from the low pressure system, it was on part numbers nothing you can see on the DME readings.

I’m thinking you have two problems at the same time. The first is some sort of issue with the fuel rail pressure; the second is your cats are faulty and restricting the exhaust system. It’s quite possible the fuel rail pressure problem is related to the damaged cat. I concur w/comment above, first step is to figure out why the fuel system pressure is being flagged.

I pulled out the spark plugs to look at them 1-3 are black and 4-6 look good. I ordered a catalytic converter for bank 1 and will replace it

Suggest caution, as if fuel problem remains, new cat might get quickly damaged. However if fuel system tests ok, your idea seems sound.


first i will put the new catalytic converter in and will let you guys know if it fixes the issue

if problem remains after putting new catalytic converter i will try unplugging rail sensor.

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Sounds like an uneducated guess. Neither the P0420 or P0430 will cause the other codes (p0133, c0300, p0001, p0171).
Are you really sure of the C0300? Because that is a propeller (drive) code. And a whole new can of worms. I’m going with it’s really P0300.
But the other codes will lead to the conditions like you posted and the P0420 & P0430.
Your treating the symptom not the disease, and that generally gets expensive. You may end up needing catalytic converters, there are at least two, P0420 & P0430, but why replace things that expensive before you find the cause? You very well may ruin the new ones in your process of guessing at the problem.

And my guess is the problem will still be there. But it’s your money and time, throw them away at your discretion.


I replaced catalytic converter. Fuel problem still remains

For some reason ecu is flooding bank 1 with fuel. Ecu thinks bank 1 is running lean. But pulling out the spark plugs 1-3, you can see they are black.

Could be an oxygen sensor

I replaced o2 sensors. Problem still remained

I’m thinking this is a problem with cars computer. Maybe it’s messed up

The car has like 140000 miles on it

I’ve had an X3 that read lean on the O2 sensor and turned out to be the DME, it showed a live reading even withe the sensor disconnected

Code p0001 came up. But wouldn’t it effect the whole engine if it was something bad with the wiring to that fuel rail sensor?

Yes , would be both banks, if you can read out or reset the adaptions you should see the “additive compensation “ reading rise on the bank that’s lean . Pull both bank precat O2 sensors and they should even out both readings