No boost after engine/turbo upgrade

[gmac78]

Another thing that happened tonight when i had the V stream chips fitted.... twice when i was giving the car some WOT action higher in the rev range, not exactly sure at what revs as wasn't paying attention but this fault code came in.

00281 Vehicle Speed Sensor G68
03-00 No signal

Now then, after the second time this fault code came in i fitted the TS tuning chips. With these chips when i reached higher revs on WOT the boost cut appeared and rev counter flicked to zero however no fault code was stored when i got back to base.

I'm wondering if this fault code was the reason for the boost cut but for some reason wasn't stored in the memory? Where as with the V stream chips fitted there was no boost cut throwing you forward but a code generated?

Getting quite tired now so time for bed . What i've written here probably doesn't make much sense but will have another read of it tomorrow.

Thanks

[Error404]

You sure your boost gauge is accurate? Sounds like fuel cut.

[gmac78]

Yeh my boost gauge is pretty accurate, i checked it against the midyvac gauge and it was spot in. The midyvac is pretty much brand new.

[twoqu]

http://www.s2forum.com/forum/showpost.php?p=525345&postcount=9

In fact read all this thread as it contains an interesting nugget that a fuel cut leaves a fault code!

http://www.s2forum.com/forum/showthread.php?t=47932&highlight=fuel+cut

Otherwise its an electrical problem.

[twoqu]

Unfortunately all these nuggets are hidden in various places. Here are the maf values you should expect if you are going to eliminate the fuel cut theory.

http://www.s2forum.com/forum/showpost.php?p=813848&postcount=20

[S2central.net]

The ECU does have a Bosch / compatible 300kPa MAP sensor ?

[gmac78]

Twoqu, some interesting reading there, cheers for that.

S2central, it's a motorola 300kPa MAP sensor i have which was new, unused in the wee box when i bought it.

Been out quading today so only got an hour or so to have a wee play with the car. Basically all i did today was clean the MAF pins, the MAF itself was bought new a few years back and has done very little since so the pins were in pretty good condition. The connector pins were removed and clean with 600 grit emery paper so should have a good contact surface now.

Starting the car in the garage and revving it to around 6k induces the RPM gauge flicker to zero along with a misfire. This only happens with the TS Tuning chips? I did another boost leak check and did find a small weep around 1.8 bar but was minimal really and doubt it would cause much of an issue. Sorted that anyway so should be nice and air tight again.

One thing i did find was a broken wire to the MFTS, not sure how long this has been like this. I did have the connector of a few days ago so could have happened then as i've never noticed it before. Anyhow, i disconnected the MFTS and revved the car to see if the RPM flicker and backfire would cease, was clutching at straws really with this hope and as such it made no difference. Still, should this not throw a fault code? It's a black wire with a blue stripe. Not too easy to see in the picture but look closely and you will see it.

Cheers

[UrS4boy]

F76 Multifunction Temperature Switch R&R Info

One thing i did find was a broken wire to the MFTS, not sure how long this has been like this. I did have the connector of a few days ago so could have happened then as i've never noticed it before. Anyhow, i disconnected the MFTS and revved the car to see if the RPM flicker and backfire would cease, was clutching at straws really with this hope and as such it made no difference. Still, should this not throw a fault code? It's a black wire with a blue stripe. Not too easy to see in the picture but look closely and you will see it.

Here is a generic review of the MFTS wiring for a 3B S2, AAN and ABY S2 (and ADU RS2):



S12 does a bunch of things:




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

http://forums.quattroworld.com/s4s6/msgs/22584.phtml

[gmac78]

Urs4boy- quick reply my friend!!! I wonder what the implications of this sensor not been powered are?

[UrS4boy]

Urs4boy- quick reply my friend!!! I wonder what the implications of this sensor not been powered are?

From the F76 info link that I provided above, there is this potential implication:

" On the ABY/ADU, the MFTS is also connected to the ECU via pin 46 of the T55 ECU connector. Using this pin as a high temp alarm (> 119 C) - the ECU cuts off active boost control as a safety measure."

Not sure if no signal = fail safe = no active boost but it certainly would make potential sense.

[twoqu]

No temp guage or overheat protection for the engine.
To eliminate the MFTS from a faulty overheat signal reducing boost to mechanical spring level, we usually remove the connector from the MFTS. So that implies that an unpowered one would have the same effect.

[gmac78]

Ah right ok, oh well i can eliminate that for my current problems. I'll get it sorted anyway at the first opportunity.

[twoqu]

Double check the WGFV. The bottom should go to the turbo, the long leg into the MAF hose and the short leg to the wastegate.

[gmac78]

Heading on the drink lads so any replies i will get back to tomorrow. Thanks for all the help so far, we'll get to the bottom of the problem yet.

[UrS4boy]

Double check the WGFV. The bottom should go to the turbo, the long leg into the MAF hose and the short leg to the wastegate.

Agree, like this:



As per clicking on the N75 WGFV label in this live Engine Bay Device map:

http://members.shaw.ca/ajmills/UrS%20Engine%20Bay%20Device%20Map.html