2013 X5 35i Random misfire problems. P0300
 

Hello everyone

OK so the car had a little hesitation in the morning so I decided to change the plugs thinking maybe it will stop the hesitation. It ran perfectly after the first start up it was just a little hesitation in the morning just a little bit. So I purchased new plugs from FCP euro and installed them. The car started miss firing on cylinder 6. Then I would reset the codes and the car would start miss firing on different cylinders. Then I decided to put the old plug back so I can see if it will fix the problem. The car at this point was not drivable. I tried switching coils back-and-forth and that did not fix the problem. Then I put the new ones back in and at least at this point the car is drivable when I drive it very slow on the very little load. Now I have a random misfires under load. If I go past quarter throttle the car will start misfiring randomly. Code is P0300. The hesitation in the morning seems to be gone. If anyone had a problem like this please help I don’t you can I don’t know what to do at this point. Thank you!

Just a thought on the random side of these misfires, since it moves around like that I’d be thinking fuel is the issue. Since the N55 is in so many BMW models maybe search for the code and N55 for more depth of field on diagnostics, fingers crossed for ya, let us know how it goes

Did you buy EXACT OE or OEM plugs?

Or some kind of 'upgrade'???

I bought bosch plugs no upgrades. They were gapped to 0.8mm 0.030 inch

dont think bosch is the OEM. NGK is.


What part number did you use?


Also, how many miles? Any notable history of issues or repairs??

Yes I’m leading towards fuel issues because I checked everything on the spark. Another thing that I’m thinking of is a faulty O2 sensor giving bad readings making the computer cut the fuel. We’ll see. Thank you for the reply!

I think you can look at fuel pressure in the Protools gauges

Where can i find protools gauges I’m not sure what that is sorry 😀

Bosch is the oem I’m pretty sure because they are the same plugs that came out of the car with same gap. Same numbers on them and everything. Not sure if they were replaced before. 81k miles on the car. There was definitely sign of work around that area but i don’t know what they were doing.

Consider googling the words 'protocols gauges'. Might be faster than posting 'what's protools' and awaiting a reply.

The ONLY code you've ever had on this car is P0300. Correct?

Do you have a BMW specific code reader? Consider buying one.

When did you buy this car? Did it have this issue? Maybe prior owner was chasing the issue, replaced plugs- but then sold?

Ard is right on target, Bimmergeeks Protools is an android based app that reads specific codes and allows you to monitor and log live data. Sorry for the confusion I must have been thinking of another post where the poster had the Protools app.

Can you pull your AFR readings???? Something like a Foxwell520 should read that.


If your fuel trims are whacked out, could be telling you fueling is a problem- too lean or rich, can cause misfires that move around.


(A DME detects a misfire by looking at the EXPECTED acceleration of the crankshaft and the MEASURED acceleration- when it sees a mismatch it says 'misfire'. As these are small variations and you get a slew of oscillations and readings with each revolution, sometimes a miss on one cyl shows up as a neghboring cyl. (Newer DMEs are better these days.) But in a car that has a lot of misses, you can see this apparentl 'moving around'.)


How many miles? Original O2s? Any other notable history??

Ok so i took the car to a mechanic and he says the fuel pressure is arond 70psi but then it goes to -70. Is it possible for the fuel pressure sensor be bad? Is it possible for the fuel pressure to go negative? I dont think it is correct me if im wrong

what did the mechanic say, in terms of why there is a -70 psi reading?