Boost, then no boost !

[RS2junkie]

Hi Guys,

Noticed the car is only giving mechanical boost, about 0.4 bar, it was fine up to about a week ago. I pulled to fault codes bit nothing. I changed the WGFV but no change.

Only other symptom is it is idling a little lower and sometimes cuts out when cold...

I tried resetting the ECU (removed the main fuse) but no change).

Its not consistent, sometimes its fine but then its not. I was expecting to find an error code but nothing.

I did notice the temperature gauge a bit erratic but not on the high side, could it be the MFT switch ?

IS there any clues as to how to track it down ???

Appreciate any advice..

Thanks

PAUL

[Error404]

I would suspect the MFTS switch, check that by unplugging it and see if you have boost back. Second on my list would be knock sensor(s).

[RS2junkie]

Alex,

Spot on... Disconnected the MFTS and the boost is back to normal... I assumed that because the temp gauge was still working that this meant the MFTS was OK, I guess not.

I am now on the search for a new one, I guess its dealer only.

Many thanks

Paul

[RichLV]

Behr MFTS's are good. I have one installed for some time already.

[Error404]

Behr was (is) the preferred option and was the OEM supplier -they all seem to read slightly inaccurately now.
If yours still works fine on the temp gauge, I would just disconnect the pin that tells the ECU the car is overheating.
You can do this most easily at the T8 connector on the firewall - the MFTS connector will usually crumble when you touch it if it's the original.
Your coil harness parts are in the post BTW Paul.

[theyagaraj]

Where would I find the mfts and what does mfts stand for,

[220bhp]

Multy function temperature sensor. big brass nut under the water rail.

[theyagaraj]

Thank you

[UrS4boy]

Where would I find the mfts and what does mfts stand for,

A little reading for you:

F76 Multifunction Temperature Switch R&R Info (with Cross Links to G62 Coolant Temp Sensor):

Click here----> http://forums.quattroworld.com/s4s6/msgs/22584.phtml

[RS2junkie]

Alex,

I have a new MFTS on order from the dealer, £120 +vat. The connector is sound but will give it a clean up when I fit the new switch...

Thanks for sorting out the coil connectors, that will test my patience.... Will let you know how I get on..

Paul

[Error404]

No problem, let me know if you need any help

[RS2junkie]

Alex,

Can you tell me more about the T8 terminal, where is it and how do I temporarily disconnect it.. ? I have a new MFTS but no time to get it fitted, so in the mean time this might be a good solution...

PS, I fitted the new coils to the coil cover today, just need to make up the terminals and then I will fit it..... The parts are perfect, by the way..... thanks..

Paul

[Error404]

Hiya Paul,

T8 connectors are the two large round ones with corrugated boots on the firewall bracket behind the ABS pump.




T8f/5 blue/white is the overtemp signal from the MFTS to the ECU (pulls to earth)
I just removed mine from the connector, heat-shrink over the terminal and tucked it back into the boot so its reversible if required in future.

[RS2junkie]

Alex,

Thanks, found the wire in the connector on the right of the two. Is it best to take out the male terminal (lower part) ? Is there a trick to removing the terminal ? there is a centre purple piece, do I remove that ? How ?


Paul

[Error404]

Hmm, think I took out the female terminal.
From memory the centre purple "spider" pops out a few mm and allows you to withdraw the terminal from the rear. I think I used a circular terminal removal tool to gently push it out from the front if that makes sense?

HTH