Coupe still wont boost above 0.4bar

[quattrodude]

also i have reset the ecu.

*i have checked for earthing fault
*replaced the sender
*checked the sender wiring
*reset the ecu and had it tested to find no fault.
*checked the timming
*checked and tested boost control valve
*bypassed the boost control valve and regained full boost so no leak is to blame.
*checked for vac leaks on return pipe to ECU

and still no better off than i was to start with!

im running out of ideas fast but need 2 sort it as its doing my box in and i need my power back

[S2central.net]

[QUOTE=quattrodude;343523]
*bypassed the boost control valve and regained full boost so no leak is to blame.
QUOTE]

SOmething not right theere - when you bypass the WGFV then boost reverts to mechanicl control in the WG - 0.4bar with factory spring. Are you sure all your plumbing is right ?

[quattrodude]

yea piping all defo in the right place as when i disconnect the thermo sender the car boosts as normal

but as for the sender itself theres not much info as to how it works and what should be going in and what should be coming out of it.

the only info i could find was the idea that a voltage is put into the sender and 2 sep. voltages come out and 1 output goes to the temp gauge in the dials and also feeds the ECU a supply and the other output feeds the auto check system to flash fault.

now from what i read up on, any voltage above 2V is normal conditions for the ECU but when the temp is above 113'c the voltage drops below 2V and shuts the boost down to factory limits on the waste gate.

And in theroy the other output also drops below 2V and throws a fault up on the dash auto check for temp alarm.

but without any other info on that sender im seeking in the dark as to if it is right or not.

The thing that gets me is when i plug the sender into the harness when fitted into the water manifold on the head i only get 0.700V when cold at both outputs when in affect the ECU is only doing its job and protecting the engine (or so it thinks)

However when i remove the sender from the manifold and just connect it up free standing im geting 7-8V on both outputs witch will allow the car to boost as normal but as soon as its earthed out when fitted i loose my voltage, and its the 3rd sender iv tryed with no success.

So why is earthing it out causing me to loose 8V when the sender works on voltage output and not earthing resistance??? (or does it work on resistance and the info i have got off the net a load of bol**x?)

it would be so much easyer just to put a boost controller on it and overide the ECU but the protection system on the ECU is there for a reason and therfore telling me there is a problem, Its just a shame it cant tell me where it is.

Does any1 have a gen. audi S2 workshop manual that can tell me how this sender works and what normal readings should be and then at least i could work out if the sender is working and move on instead of questioning if it even works.

[AndyP]

Workshop manuals are here:-

http://www.s2-audi.co.uk/work_shop.htm

[Jamo]

yea piping all defo in the right place as when i disconnect the thermo sender the car boosts as normal

but as for the sender itself theres not much info as to how it works and what should be going in and what should be coming out of it.

the only info i could find was the idea that a voltage is put into the sender and 2 sep. voltages come out and 1 output goes to the temp gauge in the dials and also feeds the ECU a supply and the other output feeds the auto check system to flash fault.

now from what i read up on, any voltage above 2V is normal conditions for the ECU but when the temp is above 113'c the voltage drops below 2V and shuts the boost down to factory limits on the waste gate.

And in theroy the other output also drops below 2V and throws a fault up on the dash auto check for temp alarm.

but without any other info on that sender im seeking in the dark as to if it is right or not.

The thing that gets me is when i plug the sender into the harness when fitted into the water manifold on the head i only get 0.700V when cold at both outputs when in affect the ECU is only doing its job and protecting the engine (or so it thinks)

However when i remove the sender from the manifold and just connect it up free standing im geting 7-8V on both outputs witch will allow the car to boost as normal but as soon as its earthed out when fitted i loose my voltage, and its the 3rd sender iv tryed with no success.

So why is earthing it out causing me to loose 8V when the sender works on voltage output and not earthing resistance??? (or does it work on resistance and the info i have got off the net a load of bol**x?)

it would be so much easyer just to put a boost controller on it and overide the ECU but the protection system on the ECU is there for a reason and therfore telling me there is a problem, Its just a shame it cant tell me where it is.

Does any1 have a gen. audi S2 workshop manual that can tell me how this sender works and what normal readings should be and then at least i could work out if the sender is working and move on instead of questioning if it even works.

Are you talking about the MFTS sensor in the coolant rail? http://www.s2forum.com/forum/showthread.php?t=24254

[4WheelDrifter]

I think you need a new MFTS.

[S2central.net]

@quattrodude - Relax. There is nothing that cannot be fixed with a methodical approach...

I asked you about WGFV 'plumbing' in reference to the series of air pipes to that device, then you come back rambling about what sounds like the MFTS (F76).

Visit the technical pages on www.s2central.net and follow the info there on the Motronic system... There are other threads on this forum which cover this subject also - they will verify what voltage you should see at the 'R' pin at normal water temps... It should be over 2V from memory - if it falls below that then the ECU thinks water temp is too high and turns off boost control - no drama.

www.s2central.net has all the schematics you need to follow up as well... Check there is no x-wired connections in T8e (or is it T8f) as I discovered that if the alarm pin into the trip computer for high temp is tied to the R-Pin then the ECU gets fooled into thinking there is a problem. BTDT as they say when exploring this one before.

[quattrodude]

i have checked the WGFV and it works fine and is piped up correctly for sure and the sender/senser i am refering to is the MFTS that is located in the coolant rail under the inlet manifold.

i understand the sender works on voltage and above 2v is good to go but the prob i have is reguardless to if the engine is hot or cold the MFTS is only giving me 0.700V at any time witch in turn is stopping it boosting.

my prob is why its only giving me 0.700V and its the 3rd sender iv tryed when it should be well above 2V.

[newsh]

On the bulkhead, near the Throttle body there's a couple of connectors in the loom to the engine, if you have moisture or corrosion in one of these it can affect the sensor voltages, have a look, clean and use some silicon dielectric grease to keep the corrosion at bay.

[S2central.net]

That'll be the two multipin cylinder connectors T8e and T8f - indeed I've seen a few with water ingress... One of those links the MFTS to the ECU - use the schematics on S2central.net for more details.

[quattrodude]

yea from memory its pins 3 and 5 and they are dry as a bone i thort just that an so traced the cables back to the multipin connectors from the sender plug.

is it poss i could have a faulty ECU and the something on the board is dragging the voltage down from the sender?