406oc.co.uk

Hi guys
After correcting a lot of small issues on one of the best cars I've ever had. 2004 406 hdi estate.
There is however still one thing that I dont get. I have read tons of pages on the topic. Pretty much all of them had a different solution. So now I'm asking you guys.
When the engine is cold. It hardly takes the gas at all.
When the temp. reaches 70 C everything is back to normal.
All filters are new, oil is new. Additives used regulary.
Any ideas?



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You always will get less power and use more fuel on a cold engine but the power loss is not normally all that noticable. The only thing I can suggest is a faulty MAF sensor as that measures the volume and temperature of the incoming air, try disconnecting the plug and see if it makes any difference.

Peter

Thx for the answer Peter.
Have disconnected the MAF. It runs much better, not perfect but better. But it is only an issue when engine is cold, not when temp is over 70.
Can the MAF sensor go partially bad?


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Yes.
Inside the MAF is 3 different points for 3 different types of information.
Air temperature, air mix, and air speed (I think)
If the MAF is disconnected then the ECU uses default information already stored.

Thx will order a new one right away.


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It may not be your problem, but if the car improves when it's unplugged then no harm done I guess.
MAFs are expensive, keep your eye our for special offer weekend deals from GSF or Eurocarparts....

barbaren wrote:Thx will order a new one right away.


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What I'd do would be to buy some MAF cleaner, and apply that.

If that doesn't work, I'd buy on a well known auction site, a good second hand
genuine ( Siemens, as I recall) MAF. Steer clear of the cheap brand new ones.
From China.

trufflehunt wrote:

barbaren wrote:Thx will order a new one right away.


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What I'd do would be to buy some MAF cleaner, and apply that.

If that doesn't work, I'd buy on a well known auction site, a good second hand
genuine ( Siemens, as I recall) MAF. Steer clear of the cheap brand new ones.
From China.

I'll second this, don't even consider the cheap eBay MAF's, they are utter shite and will feed the ECU very inaccurate data - sometimes it will perform worse with the cheap MAF connected than with none at all! May also be worth verifying that the coolant temperature sensor is functioning correctly, it is one of the engines primary sensors and if it's duff may be telling the ECU that the engine is warm when it's not, thus injecting more/less fuel than is actually required.

fattail95 wrote:

trufflehunt wrote:

barbaren wrote:Thx will order a new one right away.


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What I'd do would be to buy some MAF cleaner, and apply that.

If that doesn't work, I'd buy on a well known auction site, a good second hand
genuine ( Siemens, as I recall) MAF. Steer clear of the cheap brand new ones.
From China.

I'll second this, don't even consider the cheap eBay MAF's, they are utter shite and will feed the ECU very inaccurate data - sometimes it will perform worse with the cheap MAF connected than with none at all! May also be worth verifying that the coolant temperature sensor is functioning correctly, it is one of the engines primary sensors and if it's duff may be telling the ECU that the engine is warm when it's not, thus injecting more/less fuel than is actually required.

I dont think that maf cleaner will do much good in my case, since it is only when outside temp. is low, but will give it a go. New original sensor ordered, pretty costly but what the heck. Know all about the cheap sh*t from China, had A Mondeo begore this one, and tried some of the cheap parts from China. I guess learning is a lifelong process.
By the way coolant sensor brand new also.
But thx for all the input.


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I have used a second hand one quite successfully, as they don't very often fail the chances are that any car that's being broken will have a good one.

I used carburetor cleaner to clean mine but be careful not to touch the internals as they are very fragile.

Peter

PeterN wrote:I have used a second hand one quite successfully, as they don't very often fail the chances are that any car that's being broken will have a good one.

I used carburetor cleaner to clean mine but be careful not to touch the internals as they are very fragile.

Peter

just looked at mine and it is most certainly faulty, one of the 2 thin wires is totally eroded. Disintegrated totally from the spray from the brakecleaner can.


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Yep, you need a replacement.

Peter

Just my two penith worth, maf's should be considered as a consumable item,
By the time they've had 100k of air sucked through them there past there best,
Allways if you can afford it use a new genuine one, a second hand one maybe an improvement but
New is allways best, depends what you want from your car

dirtydirtydiesel wrote:Just my two penith worth, maf's should be considered as a consumable item,
By the time they've had 100k of air sucked through them there past there best,
Allways if you can afford it use a new genuine one, a second hand one maybe an improvement but
New is allways best, depends what you want from your car

agree


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Changed maf silky smooooth even when cold.
Thx for the help guys


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