Dog rough misfiring across the board

[na51hog]

Hi,

TLDR - sudden onset very rough misfiring across all cylinders - where to look?

My Z4 E89 35is (2011 - approx 80k) developed a misfire the day before yesterday on cylinder one (P301 misfire detected). It cleared after about half a mile and the car ran fine on the round trip. Then in the evening on a short trip out, one and two misfired - luckily it started very soon after I left the drive and I returned home in trails of glory... well actually, unburnt fuel.

So, (rashly as it turned out) to Euro Car Parts this morning at 8am for 2 spark plugs and 2 coil packs. I popped them in and... Z4 said no.

Ok, so now I am over the knee-jerk reaction, and am light a few quid to no avail, time to stop and think...

After the failed test on the drive, post spark plug and coil replacements, I noticed that errors on one and two had been joined by errors on three and six and the general code P300 Powertrain Random/Multiple misfires detected.

I am fairly confident that all the injectors didn't go bad simultaneously.

Running a Protool scan didn't pick up any additional errors over and above the misfires detected - nothing on the fuel pump and I can't see a value for oxygen sensors so I am not sure if they are reported via the ECU?

Do forum members have any suggestions about the cause of the misfiring? - what logical trail should I follow to bottom it out and will it lead inexorably to the Stealership?

Many thanks

Neil

[Reamesy]

If you can gain access to a laptop with ISTA D it will give you the fault codes and suggest a work plan to go through. This way you are trouble shooting not guessing which will be expensive.

[B21]

Given it seems multiple cylinders it’s either common electrical like cam sensor or possibly high pressure fuel pump..there are no direct diagnostics for the HPFP as it’s entirety mechanical…the HPFP rail pressure is the give away..

LPFP has limited diagnostics but no errors , doesn’t fail very often, if it does it’s the EKP usually..

HPFP failures quite common…

Otherwise you are into failing DME but decent code reader should see that

Protool would spot most major issues..

[na51hog]

If you can gain access to a laptop with ISTA D it will give you the fault codes and suggest a work plan to go through. This way you are trouble shooting not guessing which will be expensive.

Thanks - I will look to download and install

[na51hog]

Given it seems multiple cylinders it’s either common electrical like cam sensor or possibly high pressure fuel pump..there are no direct diagnostics for the HPFP as it’s entirety mechanical…the HPFP rail pressure is the give away..

LPFP has limited diagnostics but no errors , doesn’t fail very often, if it does it’s the EKP usually..

HPFP failures quite common…

Otherwise you are into failing DME but decent code reader should see that

Protool would spot most major issues..

Thanks for this. I take it you put a gauge on the fuel line at some junction and read off the HPFP pressure?

EKP?

Protool found nothing (apart from misfire) so hopefully, the DME is OK...

[B21]

Given it seems multiple cylinders it’s either common electrical like cam sensor or possibly high pressure fuel pump..there are no direct diagnostics for the HPFP as it’s entirety mechanical…the HPFP rail pressure is the give away..

LPFP has limited diagnostics but no errors , doesn’t fail very often, if it does it’s the EKP usually..

HPFP failures quite common…

Otherwise you are into failing DME but decent code reader should see that

Protool would spot most major issues..

Thanks for this. I take it you put a gauge on the fuel line at some junction and read off the HPFP pressure?

EKP?

Protool found nothing (apart from misfire) so hopefully, the DME is OK...

Protool can pick up the HPFP line pressure..there’s a pressure sensor in line ..

EKP…low pressure fuel pump controller..