BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i) - 128i Engine (N52), Exhaust and Drivetrain Modifications https://www.1addicts.com/forums/ Technical talk specifically related to the naturally aspirated engine, exhaust and drivetrain in the 128i en Sun, 16 Aug 2026 08:55:20 GMT vBulletin 60 https://www.1addicts.com/forums/images/misc/rss.jpg BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i) - 128i Engine (N52), Exhaust and Drivetrain Modifications https://www.1addicts.com/forums/ Difficult Misfire- Not the usual suspects. Desperately need your help with this puzzle! https://www.1addicts.com/forums/showthread.php?t=2251244&goto=newpost Wed, 05 Aug 2026 01:32:11 GMT Whats up family, I'm hoping for some help with next diag steps with a stubborn misfire on my N51. I've been chasing this for a few months and am running out of patience and skill to deal with it.

- 2009 128i
- N51
- Headers
- 22rpd tune
- 101k miles

Most of the car has been gone through maintenance wise. There isnt much left that hasnt been touched, inspeted, or replaced in my two years of ownership.

Symptoms:
- Began as intermittent cylinder 1 misfire (29CD). Car drove fine a week or so at a time. Misfire comes on randomly at idle and low RPM. Starts up fine, tends to start misfiring after driving a bit and then slowing to a stop it will start. The car has also died, just once, at a redlight a few months ago.

- A month later, the misfire persists but mkre stubbornly. Turning the car off, clearing codes, and then back on no longer stops the misfire like it once did. Starting back up its immediately misfiring even after sitting 6-8 hours. Then a day later, it will start right up smoothly. I cant find a pattern aside from low rpm. (Valvetronic related?)

- After doing some diagnosis with no success over a month, symptoms have worsened. I now get both 29CD (Cylinder 1 misfire) and 29CE (Cylinder 2 misfire).

Fuel trims:
- Bank 1 STFT has been as high as +15% at idle and has spiked to around +27% during deceleration from 3000rpm.
- Bank 2 also goes positive but usually stays around +10%.

I do not believe i have a vacuum leak. I have smoked intake, manifold, PCV, valve cover, brake booster hose etc. Basically everything. Only found a small leak at downstream O2 sensor on bank 1 header. I think these trims are due to a timing issue.

Things I've replaced/swapped:
- New properly gapped spark plugs
- Ignition coils (swapped between cylinders)
- Fuel injectors (swapped between cylinders)
- Valve cover (replaced twice to completely rule out integrated PCV system)
- Valvetronic position sensor (VVT sensor)
- Eccentric shaft sensor
- Vanos solenoids are OEM
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]]> 128i Engine (N52), Exhaust and Drivetrain Modifications acidstrawbz https://www.1addicts.com/forums/showthread.php?t=2251244 Supersprint Res Delete Pics https://www.1addicts.com/forums/showthread.php?t=2250650&goto=newpost Thu, 30 Jul 2026 16:01:37 GMT Anyone with a 128i and a Supersprint res delete have pictures of the underside and where it ends near the axel/diff? Trying to figure out if I can piece together a hodgepodge of exhaust components and would be good to know if i need an extender Anyone with a 128i and a Supersprint res delete have pictures of the underside and where it ends near the axel/diff? Trying to figure out if I can piece together a hodgepodge of exhaust components and would be good to know if i need an extender ]]> 128i Engine (N52), Exhaust and Drivetrain Modifications thicc3 https://www.1addicts.com/forums/showthread.php?t=2250650