I have started noticing recently that when I try to accelerate the car will initially hesitate or even slow down before accelerating. This happens with the cruise control too and a couple of times the cruise control disengaged while on the motorway. Feels like it kicks down a gear but its a manual gearbox. Idling is also rough - revs drop briefly.
Will run a diagnostic tomorrow. Could this be the EGR valve?
C5 X7 acceleration
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C5 X7 acceleration
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Re: C5 X7 acceleration
No point in guessing at this stage - any issue with the engine management can cause this - and disengagement of cruise is automatically done by the engine ECU when there is any hesitation.
Could be a sensor, electrovalve to the EGR, air or fuel issue, so pop the codes up when you've run the diagnostic.
Could be a sensor, electrovalve to the EGR, air or fuel issue, so pop the codes up when you've run the diagnostic.
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Marc
Marc
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Re: C5 X7 acceleration
Faults were under injection/ignition.
INJ : injection/ignition
State of the ECU: DCM34
Faults present : 3
P1671 : cruise control
Characterisation : information incoherent
Status : intermittent .
Location : distant .
Variables associated with the fault
Engine speed : 2240 rpm
battery voltage : 14.36 Volt(s)
ESP request status : No
gear ratio : ratio 6
measured fuel pressure : 1382 bars
accelerator pedal position : 33 %
accelerator pedal 1 voltage : 305 mVolts
accelerator pedal 2 voltage : 152 mVolts
P0088 : fuel pressure regulator control
Characterisation : rail pressure too high
Status : intermittent .
Location : local .
Variables associated with the fault
Engine speed : 2240 rpm
battery voltage : 14.36 Volt(s)
Engine status : Engine running
coolant temperature : 71 °C
fuel temperature : 25 °C
Gross measured fuel pressure : 1461 bars
measured fuel pressure : 1510 bars
HP pump flow regulator current : 833 mA
P1351 : Preheating relay circuit
Characterisation : relay controlled and spark plugs not supplied
Status : Permanent fault
Location : local .
Variables associated with the fault
Engine speed : 1120 rpm
battery voltage : 11.24 Volt(s)
Engine status : Engine running
coolant temperature : 8 °C
measured fuel pressure : 275 bars
accelerator pedal position : 0 %
supply voltage 1 : 4.99 Volt(s)
supply voltage 2 : 5.01 Volt(s)
INJ : injection/ignition
State of the ECU: DCM34
Faults present : 3
P1671 : cruise control
Characterisation : information incoherent
Status : intermittent .
Location : distant .
Variables associated with the fault
Engine speed : 2240 rpm
battery voltage : 14.36 Volt(s)
ESP request status : No
gear ratio : ratio 6
measured fuel pressure : 1382 bars
accelerator pedal position : 33 %
accelerator pedal 1 voltage : 305 mVolts
accelerator pedal 2 voltage : 152 mVolts
P0088 : fuel pressure regulator control
Characterisation : rail pressure too high
Status : intermittent .
Location : local .
Variables associated with the fault
Engine speed : 2240 rpm
battery voltage : 14.36 Volt(s)
Engine status : Engine running
coolant temperature : 71 °C
fuel temperature : 25 °C
Gross measured fuel pressure : 1461 bars
measured fuel pressure : 1510 bars
HP pump flow regulator current : 833 mA
P1351 : Preheating relay circuit
Characterisation : relay controlled and spark plugs not supplied
Status : Permanent fault
Location : local .
Variables associated with the fault
Engine speed : 1120 rpm
battery voltage : 11.24 Volt(s)
Engine status : Engine running
coolant temperature : 8 °C
measured fuel pressure : 275 bars
accelerator pedal position : 0 %
supply voltage 1 : 4.99 Volt(s)
supply voltage 2 : 5.01 Volt(s)
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- (Donor 2016)
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Re: C5 X7 acceleration
I would ignore the P1671 Cruise Control fault, as that is a likely consequence of the main fault that is P0088. Also ignore the P1351 - that is the standard Pre-Heating circuit that most HDis have most of the time.
So a few pointers for you to check - as per the fault descriptor:
So a few pointers for you to check - as per the fault descriptor:
Fault Code: Fault code P0088 Description of Fault: High pressure fuel regulation: The measured rail pressure is too high in relation to the set point. The ECU detects a difference of 180 bars to 250 bars for 3 to 6 seconds between the rail pressure set point and the measured rail pressure. Conditions for Fault to clear: Driving for 5 minutes with several full load accelerations for 10 seconds. Downgrade Modes whilst Fault is active:
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Marc
Marc
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Re: C5 X7 acceleration
From the suspected areas
Engine ECU (Software not up to date) --> probably not relevant
Poor fuel or polluted fuel (petrol, deposit, etc.) --> have been using a diesel additive for the last year
Problem on the fuel low or high-speed circuit (hose, tank, diesel fuel filter, etc.) --> air bubbles in the circuit?
Fuel injectors -->
Engine fuse box --> replaced this year
Electrical harness
Connectors
High pressure fuel pump -->
Fuel high pressure sensor -->
Engine ECU (Software not up to date) --> probably not relevant
Poor fuel or polluted fuel (petrol, deposit, etc.) --> have been using a diesel additive for the last year
Problem on the fuel low or high-speed circuit (hose, tank, diesel fuel filter, etc.) --> air bubbles in the circuit?
Fuel injectors -->
Engine fuse box --> replaced this year
Electrical harness
Connectors
High pressure fuel pump -->
Fuel high pressure sensor -->
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- (Donor 2016)
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Re: C5 X7 acceleration
So go for an Italian tune up with some heavy accelerations - as suggested to see if that will clear it up. It may be a bit of grot in the tank that has got in - when did you last have the fuel filter changed?
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Marc
Marc
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Re: C5 X7 acceleration
Changed fuel filter in Aug and I run the engine at 4000rpm 5-10min every week.
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