FAQ
TL;DR: BMW E46 316Ti N42 rough running usually traces to timing/VANOS. 3–4 timing locks are required; "Timing locks have been installed all 3/4?" Verify oil pressure, chain guides, sensors, and fuel pressure before replacing parts. [Elektroda, drdrug, post #17059094]
Why it matters: This FAQ helps E46 316Ti N42 owners fix rough running, misfires, fuel smell, and VANOS/timing faults after a collision or service.
Quick Facts
- Car/engine: 2003 BMW E46 316Ti Compact, N42B18; symptoms included rough running, fuel smell, misfire cyl 4, flashing MIL. [Elektroda, Michal2145, post #17022972]
- Logged DTCs: 2731 (inlet adjustment), 27BB (exhaust control), 28D7 (alternator comm), 27ED (ASC/DSC messages). [Elektroda, Michal2145, post #17032038]
- Chain and VANOS depend on oil; "The chain works in oil." Low pressure reduces VANOS action and tension. [Elektroda, zaxdamian, post #17037124]
- VANOS electrovalves can be rubbed by the chain during throttle, causing intake backfire and poor running. [Elektroda, Michal2145, post #17048683]
- Known N42 issue: replace tensioner and guide skids to prevent chain jump and timing drift. [Elektroda, marszałekkom, #17058714]
What symptoms did the E46 316Ti N42 show in this case?
Reported symptoms: gasoline smell from exhaust, rough running, and flashing MIL. Misfire on cylinder 4 persisted after coil replacement and swaps. Camshaft-related DTCs logged, plus alternator communication error. No ABS communication was observed after the collision. [Elektroda, Michal2145, post #17022972]
Which fault codes point to timing/VANOS issues on the N42?
Codes 2731 and 27BB indicate inlet and exhaust cam adjustment faults. These appeared alongside 28D7 alternator communication and 27ED ASC/DSC messages. They point to VANOS control or timing chain alignment issues. [Elektroda, Michal2145, post #17032038]
Should the N42 timing chain be oil‑lubricated, and what happens with low oil pressure?
Yes. "The chain works in oil." Low oil pressure prevents VANOS from adjusting and leaves the chain slack. Verify pressure before chasing electrical faults. [Elektroda, zaxdamian, post #17037124]
Can the VANOS solenoids be physically damaged by the timing chain?
Yes. Both VANOS electrovalves showed rubbing from the chain under throttle. Physical damage here explains intake backfire after revs. Replace damaged solenoids and correct the underlying chain guide issue. [Elektroda, Michal2145, post #17048683]
How do I correctly verify and set timing on the N42 after a collision?
Use the full locking toolkit to verify timing, then confirm fueling. 1. Lock the flywheel at TDC. 2. Install cam locks: rear cam blocks and front disc alignment. 3. After all locks are set, measure fuel pressure. [Elektroda, drdrug, post #17059094]
Why does my N42 smell of gasoline and backfire into the intake?
Flooding is indicated by gasoline smell. Check injection times and the lambda sensors. Connect the external temperature sensor, because it affects the fuel dose. [Elektroda, zaxdamian, post #17024681]
Does a broken lambda (oxygen) sensor cause rough running here?
Yes. One oxygen sensor was reported broken in this case. Replace it and re-evaluate behavior before deeper diagnostics. Injection times were reported within normal range during troubleshooting. [Elektroda, Michal2145, post #17024700]
How should I diagnose a persistent misfire on cylinder 4 on the N42?
Coil replacement and swapping did not move the misfire. Next, check the cylinder 4 injector and its wiring. Compression was measured at 12 bar on all cylinders, suggesting good sealing. [Elektroda, Michal2145, post #17022972]
What does alternator communication error 28D7 have to do with no ABS comm?
Error 28D7 (alternator communication) appeared with 27ED messages to ASC/DSC. After a collision, inspect power, grounds, and network lines. Repair electrical issues before blaming modules. [Elektroda, Michal2145, post #17032038]
Is there a known tensioner/guide issue on the N42 that causes chain jump?
Yes. This N42 is known for weak tensioner and guide skids. Replace them to stop chain jumping and restore timing stability. [Elektroda, marszałekkom, #17058714]
What VANOS solenoid part number is relevant for this case?
The discussed VANOS solenoid carried PN 11 36 7 560 462. The owner noted light wear on one unit after removal. [Elektroda, Michal2145, post #17032038]
Was the original poster’s problem solved, and what was the outcome?
No. The author did not solve it and no longer owns the car. [Elektroda, Michal2145, post #17156645]
If compression is about 12 bar across cylinders, where should I look next?
With about 12 bar on all cylinders, mechanical sealing looks acceptable. Focus on VANOS control, timing alignment, and fuel and spark inputs. Re-verify timing with locks and confirm injector control and sensor signals. [Elektroda, Michal2145, post #17022972]
How do I spot a damaged or shallow timing wheel on the N42?
Mechanic feedback pointed to a shallow left timing wheel. If you see misalignment despite locks, replace the left wheel. This edge case can mislead timing checks. [Elektroda, mechanio, post #17046948]
