Benelli TNT 25 Maintenance Manual page 165

Too low idle speed:
Fault Phenomenon—Instable Idle Speed with Deceleration and Flameout
a) One way valve clearance
b) Check whether idle speed bypass hole and throttle body are too dirty
Fault Phenomenon—Insufficient Power of Deceleration
a) Check whether the parameters are normal at idle speed and high idle speed;
b) Check fuel quantity in the fuel tank and fuel filter;
c) Check whether exhaust system is blocked, for example: whether three-way catalytic converter is blocked by burning
oil or damage;
d) Check fuel line pressure and nozzle;
e) Check whether fault lamp is on, and whether normal ignition can be conducted for only one cylinder
Fault Phenomenon—Slight Burning Phenomenon
Check whether the spark plug gap meets specification of 0.6-0.7mm
Fault Phenomenon—Fault lamp is on, but trouble code is inconsistent with fault
It may be caused due to instable connection of system grounding wire, reconnect the grounding wire, disconnect the power
wire of battery for 3 minutes and then connect it and start engine.
Fault Phenomenon—Extremely High Fuel Consumption
a) Check whether the oxygen sensors of two cylinders are assembled in place; if it is in the loose state, the oxygen sensor
may incorrectly judge that the combustion in the cylinder is thin, and then increase fuel, which may result in unusually
high fuel consumption.
b) After confirming that the engine mechanical parts and oxygen sensor are in normal conditions, run the engine to
observe the oxygen sensor reading. If the reading is always greater than 500 mV at normal water temperature, check
whether there is leakage in fuel injector.
Notes

The vast majority of EFI parts cannot be repaired; after the confirmation of damaged parts, generally replacement is
taken.

When starting the engine, do not operate any mechanism (including the throttle, do not pull the throttle for start) on the
engine.

If engine fault lamp becomes on during the engine operation, cause must be checked and eliminated as soon as
possible.

Do not use leaded gasoline, because lead may damage the oxygen sensor and three-way catalytic converter.

If fuel consumption is abnormal, the problem should be resolved as soon as possible, because some of the substances
in the fuel may damage the oxygen sensor and three-way catalytic converter.

Valve clearance should not be too small, if the exhaust valve is not shut off tightly, exhaust temperature may become
too high and thus shorten the life of three-way catalytic converter.

At the temperature of below 10°C, if the vehicle and engine run at low speed for a long time, the exhaust pipe may
have carbon deposits and become black, which is a normal phenomenon. It will be eliminated after a period of
high-speed operation, or appropriate means should be taken to keep the engine coolant temperature within the specified
temperature range.
 Check fuel quantity in fuel tank, fuel filter, fuel line pressure and nozzle
 One way valve clearance and confirm whether it is too small
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