V6 feels down on power

mongoose100 · Post by **mongoose100** » 14 May 2011, 16:57

Normally these things go like a scorched cat but lately it feels like its got no power down low.

Where would the best places to start looking be?

Post by **CitroJim** » 14 May 2011, 17:57

Are you sure the gearbox has not got itself running on the 'doddery old git' map?

Mine does this and then changes gear at 1500 rpm

It feels as flat as a pancake!

Otherwise, a Lexia session and a good inspection of the inlet manifold and throttle body for air leaks.

mongoose100 · Post by **mongoose100** » 14 May 2011, 18:04

Ahh Jim, was secretly hoping you'd swing by!!!

Gearbox seems fine, normally treat it like a manual by shoving it in snow mode.

Engine sounds like its straining, put it against my old 406 V6 the other day and the pug happily pulled away without too much fuss

Doesn't sound like there are any leaks, lexia shows normal. Feels like its lacking a severe amount of torque down low.

Unsure of state of plugs, will be checking air filter later today too

Post by **CitroJim** » 14 May 2011, 19:11

Reason I suggested look for air leaks is that as the manifold has to come off for the plugs often this damages the inlet manifold gasket which should be replaced every time. As the engine has a MAP sensor, any air leaks really upset the mixture.

Is the coolant temperature sensor reporting the correct temperature? Ditto the inlet air temperature sensor?

Early V6s had a little air hose spigot on the back of the manifold blanked off by a rubber cap which sometimes perishes although this was deleted around 1998. Check too the bellows between the airbox and throttle body for splits.

It may be worth checking the fuel filter as fuel starvation may be happening if the filter is clogged. It hides by the side of the petrol tank.

On an allied theme it may be worth checking the fuel rail pressure at the test point on the end of the fuel rail. If the fuel pressure is low, either because the regulator or pump is weak, that would reduce its urge considerably.

One rare cause may be collapsed baffles in the backbox. It's not uncommon on elderly ones. A clue is if the exhaust sounds really 'fruity' and deep (i.e. very bassy).

If it lost a race to a Pug (presumably not a V6) then it is a tad sick!!!

Another possible cause may be a dying lambda sensor. Our way in the UK is to ask a garage to do an emissions check, the same as they do for our MOT (yearly roadworthyness) test - this will tell if the lambda value is within acceptable limits...

mongoose100 · Post by **mongoose100** » 14 May 2011, 19:28

Bellows between airbox and manifold have split!
The pug was a V6 - are these normally quicker? Might replace fuel filter today too.

Interesting note about the exhaust too, have noticed it sounds rather bassy compared to the 406 (thats all I have to go by over here, Xantia 6's are really rare!)

Sensors appear to be showing correct temps AFAIK.

Would spraying ether around inlet areas be a wise idea in assisting leak detection? The words "BOOM" & "BANG" spring to mind here

Post by **CitroJim** » 15 May 2011, 06:55

mongoose100 wrote: Would spraying ether around inlet areas be a wise idea in assisting leak detection? The words "BOOM" & "BANG" spring to mind here

I must admit I've never tried it but knowing what ether is, I'd not like to either...

The old trick was a spray of WD40 adn watch for bubbles but the problem is that most of the potential leak areas are not accessible...

I'd, as a matter of course, replace the inlet manifold gasket when you replace the plugs. here in the UK they are strangely cheap so it's no problem to replace it every time you disturb the manifold. I hope and trust they're just as cheap down your way...

mongoose100 · Post by **mongoose100** » 15 May 2011, 08:03

Ether, the main ingredient in cans of 'Engine Start' and similar.

After reading a few things on O2 sensors, I'm wondering if that will be up for replacement - car has had the cat chopped out by previous owner too, not sure if thats a good or bad thing?

Fuel consumption is around 9/100k on the open road, swear that is a tad too high. How does yours relate to that figure?

mongoose100 · Post by **mongoose100** » 15 May 2011, 08:09

CitroJim wrote:
mongoose100 wrote: Would spraying ether around inlet areas be a wise idea in assisting leak detection? The words "BOOM" & "BANG" spring to mind here
I must admit I've never tried it but knowing what ether is, I'd not like to either...

Sorry, read that wrong! Thought you said not knowing haha. Guess that'll teach me not to rush things

Post by **CitroJim** » 15 May 2011, 08:22

mongoose100 wrote: Fuel consumption is around 9/100k on the open road, swear that is a tad too high. How does yours relate to that figure?

Trouble is Regan, I can't work in those new-fangled metric figures

Good job my 'phone can

In the old-fashioned Imperial units, I reckon 28 or so miles to the gallon (mpg) is not a bad figure for mixed driving... Funny how us Poms are supposedly metric over here but still think in imperial units - or at least I do but then I'm old!!!!

I've just tried a converter app on my HTC 'phone and your 9 litres per 100Km works out to 31mpg or 10 L/100Km works out to 28mpg so on that basis, you're running pretty much par as far as fuel economy goes...

I've heard ether-based easy start can do terrible things to diesel engines

It can make them seem addicted to it...

mongoose100 · Post by **mongoose100** » 15 May 2011, 08:38

Yeah ether and diesels dont mix.

The way I understand it is that because of the violent explosion that ether causes in the cylinders, it blows all the carbon etc away. So then you're faced with a non starting diesel with even less compression than before! Hence the addiction that they sometimes/frequently get. Hate to think what shock the conrods go thru too

Good to know bout the fuel usage too, maybe the O2 sensor is fairly ok...

Fuel filter getting replaced next few days, hopeful that may wake things up a bit