06/09/2026
BMW 430i F36 B48 2019 46k
This BMW was brought to us from another bmw specialist after a recommendation to try us.
Drivetrain warning light was on and was running horribly. Multiple misfire faults stored, already had spark plugs, coils and wiring loom with no change.
We set to work to identify the fault, after a quick going over of previous work. We quickly determined and we had low fuel pressure on the high circuit. So we decided a compression test was best to rule out mechanical faults. Just 25psi on cylinder 4. All other cylinders were fine.
Next up was cylinder leakage testing to find out where the compression may be going. This was determined that the compression was escaping into the crankcase. Opened the oil filter to find sparkles, not good. Endoscope down the bore showed no issue.
Customer authorised strip down to investigate further, we removed the engine and pulled the oil pan. Piston remains and piston rings found to prove the diagnosis. The injector on cylinder 4 had failed causing LSPI and damaged the piston lands. So now we just needed to find out if anything else has been damaged by the piston.
Pulled the cylinder head and removed the affected piston, amazingly the piston further crumbled to pieces on removal, however didnโt mark the bores at all!
New set of bmw pistons were used with new rings, new big end bearings and bolts, new oil
filter housing, coolant fl**ge, vanos solenoids (common failure points)
New head gasket and bolts, four new revised injectors installed, new gaskets throughout of course.
Engine reinstalled and battery charger connected. Air con recharge, vacuum fill both coolant circuits which held pressure perfectly.
Ista was then set up, to carry out the most important part, getting oil pressure to correct levels before starting the engine, as you can see, it takes over 12 seconds of cranking before getting oil pressure, imagine firing up a rebuild without doing this!
Hard adaptions reset carried out and secondary bleed routine carried out on the cooling system, ZF8 oil topped up at the correct temperature and she was ready.
100 miles covered post repair and zero fault codes, no leaks, car runs perfectly. 17 mpg to 47 mpg, very happy with this job and a first time fix.
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