C5 Mk1 Intermittent faults

[Monkeyfeet]

After some advice & opinions on an issue I'm having now and again on the (usually) trusty C5. Its a 2002 2.2hdi and when it runs well it, er, runs well.
But every now and again, more often lately it does the following:
Won't start first touch - starter seems to spin really fast, can just get it to catch with some throttle.
Throttle response gets a "bit on & off, can feel it lag / lose power / hesitates.
Instantaneous MPG figures drop from normal - ie yesterday around town at a steady thirty on the flat, read about 25mpg instead of over double that. When on the motorway on cruise control, say at 65mph the readings will drop from 50 ish down to 20ish then back up to normal, on the flat you can normally tell what it should be reading. (I know it varies from 20 to 99 uphill/ downhill but this is different to that.
Idle speed (ie at traffic lights) will hunt ( "sqaurewave" between normal speed and lower speed, sound kind of weird)
Doesn't sound like much, can live with most of it, but when it doesn't start it's a worry. Like on the ferry the other day...)
There's no warning lights.
Lexia gives three temporary faults. Injection :
P0402 Air circuit. Amount of air measured lower than the setting.
P0340 Crankshaft synchronising. Engine speed signal variation too sudden.
P???? Cat. converter upstream temperature signal (cat 1) s/cct to +ve or o/cct.
Prior to reading the faults I was thinking a temperature sensor (giving the bsi a duff reading causing it to mis-fuel?), maybe even fuel pressure sensor (causing bsi to, again increase / lower fuel when it shouldn't be)
Whatever it is, it's intermittent, all seemed ok on the driveway today whilst I was scrolling through Lexia.
So I'm thinking about whatever the most likely sensor is and change it? Alternative is to drive around with Lexia perm connected...
(Hopefully not fuel pressure as that's not available separately?)
Any thoughts please?

[GiveMeABreak]

If you can get all the codes and the missing one you put with P???, as any issues to do with air or fuelling may cause the engine ECU to put the car into reduced performance mode. That will restrict power and close some functions off until the issue is resolved.

No good guessing which sensors if any at this stage as a particular fault code can be a symptom of another code, which is why it is important to have them all. I can then have a look and see what they have in common or if any are related to a particular issue.

When you get the missing code, pop it back here along with your VIN.

[Monkeyfeet]

Hi Marc,
Ok will do, I'm annoyed at myself, I'd taken screenshots of the codes but had taken one of the screenshots twice - therefore no number to accompany the description of the third.
Re reduced modes - I didn't have cruise control at first, on the way back from the (a-
Cheers
Mark

[GiveMeABreak]

Yes, cruise control is one of the first things that will be disabled when there is any issue with air or fuelling (safety) and of course because the power is limited. Hopefully it will be something simple.

[Monkeyfeet]

Hi Marc,
Sorry had to be away from the PC for a while.
VIN is VF7**************[VIN obfuscated, can be read by forum staff].
I haven't been able to get the code for the third fault I'm afraid.
BTW the other day was only the first time that cruise control wouldn't work.
Thanks,
Mark

[GiveMeABreak]

The fault you have seems intermittent. When this happens the back up mode will therefore kick in and out for as long as the conditions for the fault are there, this is why your cruise control will work all the time until the fault appears again, when the engine management will deactivate it again.

Without the codes I can’t really help give you any pointers as it could have many different reasons for going into limp mode.

[Nigel w]

Hi don't know if it helps, I had a similar problem where it would lose power not to bad on the flat, but hit a hill and lost loads of power, turned out to be the MAF sensor caused loads of problems, when it happens again disconnect the wiring from the maf and see if it makes a difference if not it could be that, worth a try anyway

[sparksie]

In the absence of proper diagnostics, old school might help.
A total blockage in the airflow can cause fast cranking and, obviously, difficult starting.
One of your fault codes hints at something amiss with the air, even suggesting that the amount of air is less than requested, so before spending a fortune, it might be worth checking the air tract, all the way from the atmosphere right through to the inlet manifold.
Don't just check for obstructions, though.
The fast cranking may be a red herring, so the incorrect air mass may be caused by a split somewhere, allowing unmetered air into the engine, reducing the flow through the MAF, while actually increasing the air volume supplied.
I suspect this would need to be big enough to be obvious, to give the symptoms you have, but there are smoke kits available to find smaller leaks that may escape detection otherwise.

[Hell Razor5543]

When was the air filter last changed? Going on sparksie's first suggestion, a dirty air filter will reduce the airflow.

[Monkeyfeet]

Hi Gents,
Firstly, thanks for the replies.
The air filter is a K&N, I gave it a good wash last service, about 5k miles ago now. I've been thinking along similar lines, I'm intending to clean out the intake hoses and flush the inter-cooler with paraffin while I'm at it. When I changed the intercooler ( it had a couple of splits I couldn't repair) I noticed a lot of black oily residue in there. (Several years ago)
Before I sealed up the inlet butterfly valve housings there was always a drip onto the starter motor etc, so the engine must be pushing out some fumes out of it's breathers. Might be worth cleaning them through.
I used the car this morning, all was fine until I was nearly home, when i could feel it "pulse" and consumption read 18mpg - at 25mph on the flat.
So whatever it is, is definitely very intermittent.
Dry outside now so I'll take a look at the filter etc.
ps. All your help most appreciated!

[Monkeyfeet]

Didn't get chance to check out hoses & filters etc but did re-connect the Lexia. Even though it played up briefly earlier today ( ie idle hunting) no faults were recorded. So I'm guessing no sensor failures as such just maybe an incorrect reading?

[Monkeyfeet]

Been away working for a while, but back now to resume work on the C5.
I've tried to connect the Lexia to get some info on the C5. It gets as far as reading the cars VIN, asking for an RPO but then displays an warning message:
"The data passed from the portal is incorrect. Please check your configuration"
(screen shot available)

Now I'm sure I've altered nothing on the laptop on there doesn't seem to be much in the way of settings changes that can be made within Lexia office / Lexia itself.
Same comes up on the Xsara so it looks like it could be laptop or Lexia issues?
Any body seen this?
Otherwise I think my next step is Lexia re-installation.
Many thanks!

[Monkeyfeet]

Lexia restored!
I've read two faults, only one with an accompanying code.
1st one, from clim-regulee/ faults menu: "Fault Remote fault Intermittent fault Coolant temperature sensor incorrect value received" (no code given)
2nd one, form EDC15C2 / faults menu: "Temporary fault. Crankshaft - camshaft synchronising. Engine speed signal variation too sudden" Code on the second page for this is P0340. Recorded engine speed was 0rpm, vehicle speed 0 kph but coolant temperature was 57C, so still on the warm-up by the looks.
Whilst connected I took a look at BSI parameters. The car has been stood for a couple of days - Temperature outside air: 10C, coolant temperature: 7C and oil temperature 14C. Not sure if these differences are entirely relevant on a stopped engine but not sure why there's a 7C difference between the coolant and oil temperatures. (Outside air is about right at 10C and I'd expect a lump of metal to be lower that this considering the cooler weather we're now getting)
I've been over the hoses / tubing and have started checking through electrical connectors.
Is the P0340 code worth pursuing?