#1: P0300 Random / Multiple cylinder misfires Author: bukko, Location: SomersetPosted: Fri Dec 20, 2013 9:21 am ---- Hi all,
another fault with my missus's CC.
Is this a common fault? Seems to me like it could be anything.
I have reset the MIL but it reappears again after a week or so.
Thanks
#2: Re: P0300 Random / Multiple cylinder misfires Author: Mr-Tigger, Location: EssexPosted: Fri Dec 20, 2013 9:55 am ---- massively common,i sufferedd with this one for months. Do you have a OBD tool yourself with live data? mine eventually turned out to be the map sensor. easiest test is it should read 1bar/1000kpa when the engine is not running,mine was hitting 0.9 so was causing to overfuel and mis.
it goes on lol. have you changed anything recently?
#3: Re: P0300 Random / Multiple cylinder misfires Author: Mr-Tigger, Location: EssexPosted: Fri Dec 20, 2013 9:56 am ---- PS: when you reset the MIL with this sort of sisue you should also do a full ecu cycle/reset before running the car as it tends to be set by on-going values from the ecu and will fire straight back up if you havent reset the learning parameters again
#4: Re: P0300 Random / Multiple cylinder misfires Author: bukko, Location: SomersetPosted: Fri Dec 20, 2013 10:44 am ---- Thanks for the reply.
Not sure if my OBD reader has live data, although I have 2 so one probably does. I'll give it a go.
Haven't changed anything recently although it did have a service and MOT before we bought it a few months ago, so I would hope it wouldn't be the fuel filter or plugs, but you never know with these "services".
I didn't do the full ecu cycle/reset - how do I do that?
Having said that though, the MIL doesn't relight immediately; it always takes a while before it reappears.
#5: Re: P0300 Random / Multiple cylinder misfires Author: Mr-Tigger, Location: EssexPosted: Fri Dec 20, 2013 2:13 pm ---- if it is maf/lambda related this can happen as the MIL is triggered by a high LTFT (long term fuel trim) which slowly builds up as the car progressively overfuels and compensates for this.
To reset have the drivers window down a bit,all electricals turned off,remove key and wait for odometer/MFD to turn off,doscpnnect battery and wait (this bit is open to discussion) but i say 15 minutes. reconnect battery and then turn on sidelights and wait a minute. you'll hear a bong as soon as u do it. then reset ya clocks etc and take the car for a slow stead drive keeping around 2000rpm where possible for ten minutes for the parameters to reset.
if you cans ee live data,before you do the ecu reset look at a few things when the engine is running:
STFT (short term fuel trim)
LTFT (long term fuel trim)
and also look at MAP sensor pressure when engine is not running
by no means am i a mechanic but had fair share of dealings with this sod of a problem lol
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