C5 X7 acceleration

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

User avatar
osx
Donor 2020
Posts: 633
Joined: 08 Jun 2013, 20:09
x 6

C5 X7 acceleration

Post by osx »

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?

User avatar
GiveMeABreak
Forum Admin Team
Posts: 22618
Joined: 15 Sep 2015, 19:38
x 2341

Re: C5 X7 acceleration

Post by GiveMeABreak »

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.

User avatar
osx
Donor 2020
Posts: 633
Joined: 08 Jun 2013, 20:09
x 6

Re: C5 X7 acceleration

Post by osx »

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)

User avatar
GiveMeABreak
Forum Admin Team
Posts: 22618
Joined: 15 Sep 2015, 19:38
x 2341

Re: C5 X7 acceleration

Post by GiveMeABreak »

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:
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:
  • Deactivation of processing of the accelerometry
  • Deactivation of the accelerometry strategies
  • Deactivation of the detection of loop difference on the fuel flow rate regulator
  • Deactivation of the injector flow rate correction strategy
Symptoms:
  • Jerking/stalling
  • Unwanted acceleration
  • Noise
  • Smoke from the exhaust
  • Lack of power
  • Starting problem
Suspect Areas:
  • Engine ECU (Software not up to date)
  • Poor fuel or polluted fuel (petrol, deposit, etc.)
  • Problem on the fuel low or high-speed circuit (hose, tank, diesel fuel filter, etc.)
  • Fuel injectors
  • Engine fuse box
  • Electrical harness
  • Connectors
  • High pressure fuel pump
  • Fuel high pressure sensor

User avatar
osx
Donor 2020
Posts: 633
Joined: 08 Jun 2013, 20:09
x 6

Re: C5 X7 acceleration

Post by osx »

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 -->

User avatar
GiveMeABreak
Forum Admin Team
Posts: 22618
Joined: 15 Sep 2015, 19:38
x 2341

Re: C5 X7 acceleration

Post by GiveMeABreak »

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?

User avatar
osx
Donor 2020
Posts: 633
Joined: 08 Jun 2013, 20:09
x 6

Re: C5 X7 acceleration

Post by osx »

Changed fuel filter in Aug and I run the engine at 4000rpm 5-10min every week.