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Technical Information

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Misfiring at High Revs (59/15)

Change
Overview:

Revision

Date

Change

0

06/27/2018

•

First publication

1

04/20/2026

•

Action revised (replacement of camshafts and valve levers
instead of the entire engine)
Required parts added
Required tools added

•
•
Model Year:

As of 2014 up to 2016

Vehicle Type:

911 GT3 (991)

Concerns:

Engine malfunction (Misfiring at high revs)

Information:

•
•

Diagnostic path for fault finding in the event of the complaint “Engine malfunction”
Required repair measures

Diagnostic path for systematic fault finding
Action:
Information
The following diagnostic path relates to the topic “Engine malfunctions (particularly misfiring) at high revs
(approx. 7,000 rpm)” and is designed to help you to find possible fault causes quickly and effectively.
In particular, this involves identifying possible wear on the valve levers, which usually occurs at high engine
speeds.
If misfiring occurs even at considerably lower engine speeds or over the entire rev range, depending on the
fault memory entries stored in the DME control unit fault memory, the components that are usually affected
by this type of fault (spark plugs, ignition coils. injectors, etc.) must always be checked first in accordance
with the instructions provided under Guided Troubleshooting in the Porsche Tester.
The recommended procedure for systematic troubleshooting in “Engine malfunction (misfiring) at high
revs (approx. 7,000 rpm)” is described here in detail. For greater clarity, the detailed description includes a
condensed overview of the information in the form of a table.
Customer complaint:
•

Engine malfunctions occur during full-load acceleration at high revs (approx. 7,000 rpm).

•

The yellow warning message “Reduced power – Driving permitted – Consult a workshop” is displayed
on the multi-function display in the instrument cluster.

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The engine warning light (“Check Engine” symbol) also comes on in the instrument cluster.

•

Engine runs in limp-home mode.

•

The engine warning light and warning message disappear after switching off the ignition and then
switching it back on again (ignition reset). The engine runs normally again.

Fault verification:
If these symptoms are present, the fault must be verified using the procedure described below.
Information
If misfiring occurs even at considerably lower engine speeds or over the entire rev range, depending on the
fault memory entries stored in the DME control unit fault memory, the components that are usually affected
by this type of fault (spark plugs, ignition coils. injectors, etc.) must always be checked first in accordance
with the instructions provided under Guided Troubleshooting in the Porsche Tester.
•

Read out the fault memory using the Porsche Tester: In the DME control unit memory, the fault entry
P0300 – Misfire totals error is together with a fault entry P0301 ... P0306 (Misfire cylinder 1 ... 6) is
stored.

•

Create a Vehicle Analysis (VAL) using the Porsche Tester.

•

Test-drive the vehicle until the fault occurs: Full-load acceleration in 3rd gear (manual transmission)
over a rev range of 4,000 – 8,500 rpm.

•

Reproduce the fault: The fault can be reproduced again – always in the same rev range (+/- 300 rpm) –
as described above.

Actions:
1

2

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The fault cannot be reproduced:
•

There is a high probability that the malfunction is not caused by wear on a valve lever. Another
component must be checked in order to determine the cause.

•

If necessary, talk to your contact person for technical enquiries at your importer’s office in order to
decide what to do next.

The fault can be reproduced:
2.1

Swap the ignition coil and spark plug from the problem cylinder with the ignition coil and spark
plug from a cylinder that is working perfectly.
For procedure, see: ⇒ Workshop Manual '282020 Removing and installing ignition coils' and ⇒
Workshop Manual '287020 Removing and installing spark plugs'.

2.2

Test-drive the vehicle and try to reproduce the fault again under the conditions specified above.

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Then read out the fault memory of the DME control unit using the Porsche Tester and check
whether the same fault memory entry is stored again, i.e., whether, after swapping the ignition
coil and spark plug, the cylinder that was previously the problem is now working perfectly and
the fault occurs instead on the cylinder into which you installed the ignition coil and spark plug
from the cylinder that was originally the problem.
•

If YES (the same fault is stored again): Remove the ignition coil from the cylinder that is
now the problem and install it again in the cylinder that was originally the problem. Leave
the spark plug in the cylinder that is now the problem. Then test-drive the vehicle again
and reproduce the fault again in order to clearly identify the component that is causing the
fault.

•

If NO (the cylinder that was originally the problem is still the problem): Remove the
cylinder head cover on the problem cylinder bank and check the camshafts and valve levers
for visible signs of wear. For procedure, see section ⇒ Technical Information '287020
Checking camshafts and valve levers for wear'.

Summary:

Customer complaint
•

Engine malfunctions occur during full-load acceleration at high revs (approx. 7,000 rpm).

•

The yellow warning message “Reduced power – Driving permitted – Consult a workshop” is displayed
on the multi-function display in the instrument cluster.

•

The engine warning light (“Check Engine” symbol) also comes on in the instrument cluster.

•

Engine runs in limp-home mode.

•

The engine warning light and warning message disappear after switching off the ignition and then
switching it back on again (ignition reset). The engine runs normally again.
Fault verification

•

Read out the fault memory using the Porsche Tester: In the DME control unit memory, the fault entry
P0300 – Misfire totals error is together with a fault entry P0301 ... P0306 (Misfire cylinder 1 ... 6) is
stored.

•

Create a Vehicle Analysis (VAL) using the Porsche Tester.

•

Test-drive the vehicle until the fault occurs: Full-load acceleration in 3rd gear (manual transmission)
over a rev range of 4,000 – 8,500 rpm

•

Reproduce the fault: The fault can be reproduced again – always in the same rev range (+/- 300
rpm) – as described above.

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Fault can be reproduced

Fault cannot be reproduced

•

Swap the ignition coil and spark plug from
the problem cylinder with the ignition coil
and spark plug from a cylinder that is working
perfectly.

•

There is a high probability that the malfunction
is not caused by wear on a valve lever. Another
component must be checked in order to
determine the cause.

•

Test-drive the vehicle and try to reproduce
the fault again under the conditions specified
above.

•

If necessary, talk to your contact person for
technical enquiries at your importer’s office in
order to decide what to do next.

•

Check whether the same fault memory entry is
stored again.

•

If YES: Remove the ignition coil from the
cylinder that is now the problem and install
it again in the cylinder that was originally the
problem. Leave the spark plug in the cylinder
that is now the problem. Then test-drive the
vehicle again and reproduce the fault again in
order to clearly identify the component that is
causing the fault.

•

If NO: Remove the cylinder head cover on
the problem cylinder bank and check the
camshafts and valve levers for visible signs of
wear. For procedure, see section ⇒ Technical
Information '287020 Checking camshafts and
valve levers for wear'.

Checking camshafts and valve levers for wear
Work Procedure: 1
2

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Remove the cylinder head cover on the affected cylinder bank.

⇒ Workshop Manual '158219 Removing and installing cylinder head cover'
Check camshafts and valve levers for visible signs of wear.

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The following problems indicate a worn valve lever:

3

•

Rough surface on the cams of the cylinder in
question. If there is a significant amount of wear,
the contour of the tip of the cam will be “square”
and will show significant tempering colors
(blue/brown discoloration of the material caused
by high temperatures).

•

The valve lever shows significant signs of linear
Þ Wear on
wear on the contact surface to cam ⇒
Wear on valve lever
valve lever -Arrow- at the edge of hydraulic valve
Þ Wear on valve lever -Magnifier-. The black coating is worn
clearance compensating element ⇒
down and the silver base material can be seen.

If there are visible signs of wear on the camshafts and/or valve levers:
Create photo documentation and replace all camshafts and all valve levers.
3.1

Þ Wear on valve
Take photos of the damaged areas on the camshaft and associated valve levers ⇒
lever -Arrow-. Make sure that the photos clearly show the installation position of the valve levers
in question.
Also indicate the installation position of the
valve levers in question (e.g., cylinder 6 –
intake) or identify the components by labelling
them ⇒ Marking valve levers.

3.2

Document the photos together with the
Vehicle Analysis Log and the engine number of
the vehicle in the related PQIS job.

3.3

Replace camshafts and associated valve levers
and then re-program the DME control unit.
For procedure, see: ⇒ Technical Information
'158219 Repair measures'.

Marking valve levers

Repair measures
Work Procedure: 1

Replace camshafts and associated valve levers.
For procedure, see: ⇒ Workshop Manual '150520B7 Removing and installing camshafts (includes
setting timing)'

2

After replacing the affected camshaft and the associated valve levers, re-program the DME control
unit with the Porsche Tester and installed Porsche Tester test software 15.700 (or higher): DME control
unit> ⇒ ‘Programming’ menu >> ‘Automatic programming’ function.

3

Change engine oil and oil filter. ⇒ Workshop Manual '170155A6 Engine oil and oil filter change'

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After completing the work, carry out a test drive until the engine reaches operating temperature.
Information
To confirm the successful repair, during the test drive, specifically drive in the rev ranges in which the
original complaint occurred.

5

Parts
Information.:

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After carrying out the test drive, use the Porsche Tester to create a Vehicle Analysis Log (VAL) and
Þ ‘Data management’>‘VAL data return’ using the Porsche Tester to send it to
select the function ⇒
Porsche AG.

Required parts for checking wear on the camshafts and valve levers:
Part No.

Designation
– Location

99907344301

⇒ Screw with washer assembly, M12 x 1.5 x 40
– Diagonal strut screw connection

2 pieces

99907286901

⇒ Hexagon-head bolt, M12 x 1.5 x 45
– Diagonal strut screw connection

2 pieces

99908412309

⇒ Hexagon nut, M10
– Screw connection securing anti-roll bar to
connecting link

2 pieces

90007606402

⇒ Hexagon nut, M8
– Screw connection securing anti-roll bar to body

4 pieces

99907286801

⇒ Hexagon-head bolt, M12 x 1.5 x 80
– Screw connection securing rear-axle cross
member

2 pieces

99907285901

⇒ Hexagon nut M12 x 1.5
– Screw connection securing rear-axle cross
member

2 pieces

99908444501

⇒ Hexagon nut, M10
– Screw connection securing rear-axle cross
member

4 pieces

99907605301

⇒ Hexagon-head bolt, M12 x 1.5 x 58
– Transmission carrier screw connection

2 pieces

99908600902

⇒ Hexagon nut, M12
– Transmission mount screw connection

1 piece

N 90848405

⇒ Hexagon nut M12 x 1.5
– Engine carrier screw connection