Quote:
Originally Posted by BadContrakt
2008 N54 AWD 140k miles
DCI
Catless DP
Stage 2 MHD tuned (stock intercooler)
On cold start in the mornings before work, my idle is funky. Car starts normally and does cold start high idle normally for ~7 seconds then the idle fluctuates uppppppp like 3-400 RPMs and thennnnn droppppps back downnnnnn to 800 then a few seconds more drops down again to standard idle of 650 and stumbles and rumbles and misfires.
Then I tap the gas a couple times and it all evens out.
This had NEVER happened until the MORNING AFTER I installed my catless DPs. Didn't touch plugs, coils, or fueling in any way shape or form. Plugs are standard non-iridium tipped Bosch with 10k miles on them and coils are standard OE Delphi with 10k miles on them. Injectors are probably factory. Most likely not index 12.
I thought maybe because I'm missing the downstream O2 sensors now, maybe the car is just acting funky because of the Service Engine Soon light. So I tuned MHD and coded out the O2 sensor light. Nope. Still misfiring on cold start.
I understand colder plugs and their function and I understand why they're necessary for higher boost applications but I don't understand why they'd be needed for a cold start idle. Do I miraculously have leaky injectors the day after installing DPs/tune and the misfire isn't related at all to the DPs or the tune? Just ridiculous. One thing after another.
PS:
BMS says "Note: these plugs are on national back order. Most still floating around the internet are counterfeit. We suggest the NGK 2-STEP plugs as an alternative for all tuned BMW applications."
I doubt with simple bolt ons I should be running 2 step colder plugs? Does anyone do this?
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If BMS says 2 step colder is fine then you should be good.
I run 97506s and they work great.