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BMW 520i rough idle after injector replacement

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ENGINE

BMW 520i rough idle after injector replacement

GP

GaragePro DXB Verified workshop · Dubai

Vehicle Information

Make and model BMW 520i

Year 2021

Engine 2.0L Turbo

Mileage 83,400 km

Problem Description

The vehicle arrived with a misfire on cylinder two. All four injectors were replaced and coded using ISTA. The misfire fault has disappeared, but the engine now shakes heavily at idle.

The vehicle drives normally once the engine speed rises above approximately 1,400 RPM. No warning lights are currently displayed.

Fault Codes

P0171 118001

Work Already Completed

Injectors replaced and coded, spark plugs checked, ignition coils swapped between cylinders, adaptations reset and smoke test completed. No obvious external vacuum leak was found.

12 Mechanic Replies

AK

Ahmed Khan BMW Master Technician · 1 hour ago

Check the crankcase ventilation diaphragm inside the valve cover. On this engine it can leak internally without showing clearly during a standard smoke test. Monitor crankcase pressure and temporarily block the breather line to see whether the idle improves.

MS

Mohammed Saleh Independent Diagnostic Specialist · 47 min ago

Compare the injector correction values and short-term fuel trims at idle and at 2,000 RPM. If the fuel trim drops significantly above idle, you are almost certainly dealing with unmetered air.

JD

James Diagnostics Automotive Electrical Expert · 28 min ago

Confirm the injector calibration numbers were entered against the correct cylinders. I have seen the engine run without codes when two injector compensation values were accidentally reversed.

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Ahmed Khan suggested checking the crankcase ventilation diaphragm.

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Rehan Ahmad

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Dubai, United Arab Emirates

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ENGINE ELECTRICAL DIAGNOSTICS BMW

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BMW 520i rough idle after injector replacement

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BMW 520i rough idle after injector replacement

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BMW 520i rough idle after injector replacement

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Rehan Ahmad

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