406 hesitation

saabsalltheway! · Post by **saabsalltheway!** » 21 Jul 2008, 15:40

hi i have a 406 2.0l 'p'reg
the problem with it is it hesitates at mid revs just seems flat with no power.lift off a bit and it seems to take off a little bit then flat again. its been to a couple of garages one a peugeot specilest and the couldnt find anything wrong so just changed the fuel filter
any help would be great
thanks paul

AndersDK · Post by **AndersDK** » 21 Jul 2008, 18:19

Sounds to me like a defective or garbled MAP sensor.

This sensor is reponsible for the ignition timing advance when the engine is commanded to accelerate.
If the ignition does not advance, the engine may even stall if you try accelerate.
The MAP sensor takes the place of the vacuum advance pod on earlier carburettor engines.

The MAP sensor is a pressure sensitive device, and can be partly blocked/garbled by heavy/sticky oil residues from the engine fumes venting.

It can of course simply fail any reason like any other mechanical component.

saabsalltheway! · Post by **saabsalltheway!** » 21 Jul 2008, 18:43

hi
is it easy to clean the map sensor and where abouts is it located on the engine
thanks for the reply
paul

Post by **CitroJim** » 21 Jul 2008, 18:48

Hi Paul, welcome to the forum! What's with all this Saab nonsense in your username

I'm not too familar with your engine but many have the MAP sensor mounted on the end of a length of thin pipe. This pipe often perishes and admits air, thus upsetting the operation of the MAP sensor. It can get blocked too.

You have the symptoms of a weak mixture. It is worth spending some time looking for air leaks around the inlet manifold beyond the throttle body and whilst you're looking around that area, give the throttle body and it's air passages a good clean up with some carb cleaner. You'd be surprised how much carbon and rubbish collects there.

Also give your idle control valve a clean-up as well.

Did any of the garages run diagnostics on your ECU? If so, did any faults show up?

Finally, if all this is negative, you need to look at your fuel rail pressure and the operation of the pressure regulator. Your fuel pump may be getting a bit weak and unable to deliver the necessary under accelleration.

saabsalltheway! · Post by **saabsalltheway!** » 21 Jul 2008, 20:05

thanks citrojim
as you probably guessed im a saab driver

i brought this car off a freind cheap and thougth i will do mot work and any other bits and sell it on so took it for mot and it passed

so now its just this slight engine problem i need to sort out. and now i'm in the hands of the peugeot gods.
so now i will start to look at map sensor and air leaks.
garages didnt do any diagnostics checks.
was thinking of taking inlet manifold off to clean every thing up is this a good idea or not.
thanks again paul

AndersDK · Post by **AndersDK** » 21 Jul 2008, 20:24

Your P 406 2L would be a multipoint 16valve ?
In that case the MAP sensor would be located down under the "banana" lump somewhere - according to servicebox.

You may register yourself on servicebox to get free parts & price info on your 406.
http://public.servicebox.peugeot.com/
If you register as indepedent mechanic/garage - you dont need any vat/tax numbers i.e. anyone can register this way.

saabsalltheway! · Post by **saabsalltheway!** » 23 Jul 2008, 01:09

hi everyone
yes found the map sensor under the manifold took it out and gave it loads of carb cleaner also took throttle boby off and cleaned that along with the idle control valve but not had time to take it for a run.
couldn't find any air leaks.
will keep you posted with what happens next.
thanksfor your help PAUL

Post by **CitroJim** » 23 Jul 2008, 08:04

Keep us informed Paul

If all that lot has not helped, It might be a good time to try a new lambda (oxygen) sensor although before doing that, It will be good to have a quick diagnostic session on the ECU.

saabsalltheway! · Post by **saabsalltheway!** » 23 Jul 2008, 09:41

thanks will keep you informed just wondering if there is some way i can diagnose it my self as i didnt want to take it to the dealer and i no its got a 21? pin socket not like the newer 16 pin obd sockets thanks again

saabsalltheway! · Post by **saabsalltheway!** » 24 Jul 2008, 15:58

Hi again
just to let you all no ive managed to take the car for a good run and it seemed to get better and better but its still not right so im thinking of taking map sensor out again and giving it another clean

thanks again for all your help 8) you are the peugeot gods
and with referance to my user name,ive seen pug205grd on the saab forum i use and i think he's also got a saab.
good luck and keep up the good work

PAUL