LI01.30-P-075439

M139 Engine: Poor Performance Due to Broken Valve Spring(s)
Topic number
LI01.30-P-075439
Version
1
Function group
01.30 - Cylinder head
Date
10/17/22
Validity
All vehicles equipped with M139 engine
Reason for change
Complaint
Customer may complain of a CEL on in the instrument cluster, rough running, trouble starting, issues with ECO stop/
start or a combination thereof.
Cause
One or more broken valve springs in the cylinder head.
Remedy
Work through the guided tests for any relevant fault codes.
For misfire related fault codes this will include:
•
Inspecting the injector performance data for abnormalities
•
Using a smoke machine to inspect for air leaks
•
Performing a compression and leakage test
Depending on the severity of the failure, a broken valve springs may be able to be found in a compression/leakage
test. If not it may also show up on a PICO running compression test.
To verify the best method is to remove the cylinder head cover and inspect the valve springs directly
If a broken valve spring is found:
•
•
•
Inspect the valve, rocker, retainer, and keepers on that assembly for damage.
Inspect the camshaft and camshaft lobe that operates that valve
Inspect the piston face via borescope for piston/valve contact
Also perform a leak test once the valve is able to be fully seated to ensure no damage to the valve or seat has occurred.
If no damage to the piston or valve seat has occurred, replaced the damaged components and release the vehicle.
If valve seat or piston damage has occurred please open a PTSS case, upload the results of all tests, and outline
what work has been conducted thus far.
17.10.2022 22:08:05
© Copyright Mercedes-Benz AG
HENRAND
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Symptoms
Power generation > Engine management > Indicator lamp > Engine diagnosis > lit
Control unit/fault code
Control unit
Fault text
N3/10 - Motor electronics 'MRG1AMGR4' for combustion P030100 - Combustion misfiring of cylinder 1 has been
engine 'M139' (ME) (MRG1AMGR4)
detected. _
P030200 - Combustion misfiring of cylinder 2 has been
detected. _
P030300 - Combustion misfiring of cylinder 3 has been
detected. _
P030400 - Combustion misfiring of cylinder 4 has been
detected. _
Operation numbers/damage codes
Op. no.
Operation text
17.10.2022 22:08:05
© Copyright Mercedes-Benz AG
Time
HENRAND
Damage
code
Note
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