Mine's pinking under load. It revs freely but when accelerating on the road it pinks noticeably - the old bucketful of screws noise from up front.

I called the Citroen dealer who last serviced it not 1,000 miles ago and explained the situation. He said that he'd had a number of calls recently from other owners complaining about the exact same symptoms, and that as soon as I could I should probably change my garage and start using Super Unleaded.

Not the crappy Tesco fuel thing again I hope

I wondered if anyone else had encountered the same thing. In addition, the poor old girl won't idle properly when first started - it really feels like it's going to die when you select D or R and tap the throttle. Never used to do it.

Cheers! Phil.

A fault in your ignition system is one of the most likely causes of the engine pinking but
with all other variables untouched since you last had the car serviced I can't see many
immediate causes of this problem; it could be another dodgy batch of fuel if others are
encountering the exact same symptoms; I don't believe in coincidences.

Changing the fuel provider is certainly the easiest most immediate thing you can try unless
you're running on a full tank, Xm tanks can hold a fair whack!!

It calls for a dose of Redex then a trip to the garage to check out the plugs/leads/timing
/injectors. I can't see the engine would be suffering from bad carbon build up at the mileage
of your car and it would more likely be split air hoses etc.

Andrew

Aw sh*t, I just started using Tesco again to try and save pennies and because the queues seem to have dropped recently, maybe that is a mistake.

I used to always fill mine up to the brim on every trip to the garage, but more recently I've just been 1/2 filling it or less depending on the time of the month, plus I'm running 2 again now and don't wanna end up with too much cash in the form of fuel in one I'm not using.

Then again, back last year when there was a potential fuel shortage on, I DID have both of them full to the brim, almost a hundred per tankful back then.

I remember when there was a previous shortage back in 2000ish I was lucky, had just filled the prestige up and managed to last until the shortage was over without any queuing.

Have about 3/4 still left in the tank and when I think about it I've only been aware of the problem since filling up.

As you say the tank is blimmin huge - one of the things I love about the car - but I may start mixing in some new super unleaded on Monday.

It's an 'independent' station so in future shall only be using them for air and hand washes

This is strange. Firstly, I ve never heard of an XM that demands super grade fuel; my Turbo CT running plus 1 bar runs happily on regular grade and so does my V6. Secondly, doesn't your car have a knock detector that automatically retards the ignition if pinking occurs?

Has any other petrol XM owner ever suffered from pinking? I think I'd be looking elsewhere.

Derek

Not sure. Something's definitely up with it though

Hi all

I wouldn't be blaming the fuel for the exact reason Derek has mentioned, but try the higher octane stuff first just in case. Any engine with computer controlled ignition and fuel injection should be able to detect and prevent pinking and knocking, and an engine of this age should not have or be capable of creating carbon build up to the point where it would cause this problem.
Although having said this i always run mine on 97ron because it feels more responsive and smooth.
Not helpful, but there is a handy thread on here about water injection that may be of help

Hope its cheap,

D

Hi Phil, it's even more strange as your car is an auto. They will usually change down way before the conditions that might cause pinking.

It might be worthwhile having the ignition timing checked in case it's slipped.

As an aside, when I discovered that my V6 had a knock detector I worried that maybe I was degrading the performance by using 94 RON, particularly when towing our caravan. So before the next caravan run I filled up with "best", there was no detectable difference in performance an no improvement in fuel consumption. I now carry on using regular grade.

Derek

Strange how you noticed no difference Derek, i watched an episode of 5th gear once where they run an old fiesta, astra and a subaru inpreza and something else, basicaly two old bangers and two high performance cars and there was a marked improvement for the bangers and no difference at all for the more powerfull cars when run on 99ron as apposed to 95 strange that, must be the way the engine is setup?

D

Hi Dean, yes, when towing my V6 tends to run for long periods in auto 3rd gear unless I force it into 4th by switching to "snow" mode. I had hoped that by changing to super the expected performance increase would solve the problem - it didn't.

Derek

Thanks for the replies chaps.

I was listening to the noise intently this morning and I ended up convincing myself - as one often does in these situations - that it might not actually be pinking, particularly after everything that's been said here with regard to anti-knock. Could it be anything else? It's most noticeable when the engine is cold and is only evident when accelerating. You can bring the noise on by pushing your right foot down only very slightly and turn the noise off again by bringing your foot back up. It's been a long, long time since I've been in a car that pinked so I'm a bit lost.

Sounds a simple thing, but has it had new spark plugs recently? That can cause rough idle and a pinking noise.

Id lost track of when mine had been replaced, when i fitted some new NKG plugs the old ones looked quite tired. It went much better and ran much smoother after a good service and new plugs. It always gets serviced but i think id left the plugs in a little long.

The 16v engine is always a very smooth, quiet engine, i cant say ive had either problem with my Xm. Oh another thing you could try to help your idle problem, is clean the air intake, i use Forte intake cleaner, works a treat! I do it with all of our cars and always notice a difference in smoothness, performance and fuel economy afterwards.

On the tesco fuel thing, i heard of someone who, last week, filled up with diesel from his local Tesco, drove 10 minutes down the road and the car stopped. His garage towed the car in and investigated the problem. It turned out it wasnt diesel that he got from Tescos but a tank full of kerosene! WHich destroyed the fuel pump, hence the car stopping. So there is a rather large bill now, which Tesco will be receiving, and no doubt everyone else who used the same tank that day.

I never ever use supermarket fuel, its no cheaper (not round here anyway) to shell, which i always use. I did used to use Tesco fuel years ago in my old AX, (which pinked actually!) and i always found id get far more miles from Shell over tescos.

It was you telling me the engine was smooth and quiet Chris that prompted me to get it sorted. Turns out the pinking noise wasn't pinking at all, but was some sort of sprung-loaded metal vent/vale on the manifold that was rattling under acceleration. If someone could explain what the hell this actually does I'd be grateful

The poor idling was caused by the idle control stepper motor.

I have the old girl back and it's like a new car

Glad you have it sorted out Phil, the 16v seems like a great engine, mine is so smooth and quiet you would tink its a new car.

sprung-loaded metal vent/vale on the manifold? What do they mean by that? Not the throttle body?!