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      08-26-2011, 04:44 AM   #1
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Drives: E92 335xi
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Diagnosing jerking/misfire above 3psi - injector DIY a possibility?

-2008 335xi
-catless DPs [installed 1,500mi ago]
-Procede V5 rev2a, 7-29 maps [autotune on] [installed 1,500mi ago]
-HPFP recall 1,500mi ago + at 30,000mi
-Injector recall at 30,000mi
-Techron fuel system treatment 1,500mi ago

I'm out of warranty, out of cash, and trying to diagnose a jerking/stuttering when at and above ~3psi boost. During start-up and conservative driving under 2psi boost, all is normal. Above that, the car jerks/misses 3-10 times within ~10sec of moderate acceleration (50% throttle). If I got WOT, power is greatly reduced (feels like ~180HP) and it runs like it's on 4 cylinders and the engine out of balance, missing (I think) badly. It will run like crap through the whole power band for 5min after a WOT run, which makes me suspect that a bad injector may be spraying fuel on a plug-- just a wild guess. No codes thrown, even with Procede removed. With Procede installed [CANclear off], the SES light flashes orange, but I get no codes when hooked up to my computer. I checked the spark plugs (~10kmi old), all are great except for a bit of fouling on #6. I removed & replaced the coils one at a time while idling , all caused stumbling, so they seem to be working. All contacts on the coils and plugs are clean, dialectic grease conservatively applied at the plug/coil connection + a very very small amount of anti-seize on plug threads (BMW tech said this is ok).
I did the intake valve cleaning DIY, VANOS cleaning DIY, and cleaned the 2 MAF sensors (gently, of course). The jerking/missing was not alleviated. I've read that leaks upstream of the wastegates can cause similar issues-- It's hard to diagnose that. Most all connections on the driver side were messed with during the intake valve cleaning and they are now firmly connected. I suppose a smoke test at a shop or charging the system with compressed air (air tool nipple threaded into pvc end cap at end of FMIC line) may reveal any leaks.

The issue remains despite all the cleaning, tune removed, plugs + coils checked, so I'm led to believe it's a fueling issue. It's very frustrating to not get a DME code. HPFP, injectors, or maybe O2 sensor? My previous HPFP and injector failures had both affected my start-up and idle, but start-up is fine right now.

Has anyone attempted to replace injectors on their own? I've read that replacements need to be calibrated somehow at the dealer. Is there any possibility this coding can be a DIY using software like NCS Expert? Would doing the swap, then driving 5mi to the dealer be possible?

What's the cost to have the dealer perform an injector pressure test? HPFP test as well?

I took it to the dealer for diagnostics. My SA was off today so I don't have the details, but the invoice mentions multiple misfire faults cylinders 1-6. O2 sensors reading out of spec. Recommend adjusting vehicle back to OEM (I have catless downpipes), coding and programming system prior to any further diagnosis. I just checked my O2 sensor wiring to make sure I didn't reinstall them wrong during the DP install. Both black wired sensors go to Bank 1 (front) and the grays to bank 2 (rear). I'm not sure where to go from here, I really dont want to remove the DP's; it's an XI so it was a real PITA.

Last edited by tahoerdr; 08-30-2011 at 02:09 AM.
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      08-26-2011, 11:51 AM   #2

Drives: 2006 330i
Join Date: Jun 2011
Location: Victoria, BC

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After sitting all night (hot soak) it starts perfectly fine in the morning?

I would wipe the anti-sieze off all plugs and the plug threads in the block, or at least plug 6 and the threads for plug 6 as it may be causing a grounding issue.
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