Changed spark plugs to Iridium IX (Part#6441) and I can't believe the difference.
Back story: The car came with about a year old "tune-up" from previous owner which he purchased from FCP (Bosch coils and spark plugs)
https://www.fcpeuro.com/products/bmw...12138647689kt4 and gave me the original parts with receipts. Never really looked at it.
I've been battling cold start misfires and poor idle for months now and never even considered spark plugs just because of benefit of the doubt. I've tried everything possible to try and cure this misfire and poor idle and even had done the VSS and asked the mechanic to check if my plugs were good which he said they seemed ok besides the oil coating due to the leaking valve stem seals.
Well having tried everything possible, it was time to see if so called "new" plugs could be the culprit and decided to open the box the previous owner gave me.
And what do ya know?!! Looks like the PO only replaced 4 out of the 8 for whatever reason!!!
Pulled the plugs and laid them in order and all the plugs that were misfiring were original BMW Bosch and the rest the new Bosch (both same part#FR7KPP332).
So put it the new Iridium IX, cleared all DTC and fired it up for a test drive and wow. What a difference!!!
Throttle response is instant, now it pulls much harder than before and idle purrs like a kitten and getting city MPG of 12 much easier than before (used to be 9-10 unless really feathered it). Didn't experience the cold start misfire as it only happens in the mornings but we'll see.
