Boost stops at 1.4bar - N75?

[hunker7]

Just did the output test...test. N75 clicked as it should

Should i try putting the old one back, and see if that works?

[UrS4boy]

But it's not N75 at fault then? It's something else causing N75 not to work?

Please stop asking us to speculate what the issue is until you have shown us that the ECU is connected to and is controlling/talking to the N75 by completing the output tests. Until then you are just asking us to waste our time.

Sorry but that is how I see it.

[hunker7]

Will do tomorrow

But it's not N75 at fault then? It's something else causing N75 not to work?

[igor136]

http://www.youtube.com/watch?v=SNwqbyQZzfY

[UrS4boy]

20VT Output Test Procedures

I have not done that yet.

Man, you have to do this:

SJM Autotechnik: Output Tests - 1992-96 S4/S6 with AAN 5 cylinder 20V Turbo Engine

http://www.sjmautotechnik.com/trouble_shooting/ecuf20v.html#outs4

There is an ECU "output test" mode that will cycle the engine electrical solenoids on and off to verify they are working correctly. You are able to test the 5 Fuel Injectors Idle Stabilizer Valve (ISV) Carbon Canister Solenoid Valve Waste Gate Solenoid (waste gate frequency valve) .



To activate the Output Tests, you must first connect the Jumper Wire across the Fault Code Connectors as shown in the above diagram and THEN turn on the ignition to initiate the output tests. (DON'T START THE ENGINE). After the ignition is turned on, remove the jumper wire after at least 4 seconds.
• FUEL INJECTOR TESTS: After you have removed the jumper wire, you can place your fingers down on fuel injector #1 and then open and close the throttle with your other hand. You should hear and feel #1 Injector click 5 times and then be quiet, place your fingers on Injector #2 and again open and close the throttle, Injector #2 should click 5 times, place your fingers on Injector #4 and open and close the throttle, Injector #4 should click 5 times, repeat for Injectors #5, then Injector #3
• After doing the last injector test on #3 the Output test will switch to testing the IDLE STABILIZER VALVE (ISV). You should hear this Idle Stabilizer Valve clunk open and closed..
• Connect the jumper wire again for 4 seconds to go to the next output test:
• The blue Carbon Canister valve behind the idle stabilizer valve (behind throttle area) will be cycled on and off. You may want to place your hand around the carbon canister valve to feel it operate.
• Connect the jumper wire again for 4 seconds
• The Waste Gate Solenoid on the intake boot near the turbo inlet will be cycled on and off. This valve operation is pretty loud, so you should be able to hear it operate.
• Connect the jumper wire again for 4 seconds.
• ;End of Output Test Procedure, fault code memory has been cleared.
• NOTE: To repeat the Output tests, the ignition should be turned off for at least 20 seconds. If Output tests are repeated, the INJECTORS will NOT be cycled again, unless the engine is started and run briefly.

DO IT!!!

[hunker7]

Have you done the ECU device stimulation check yet to establish that your ECU is talking to the N75?

http://www.sjmautotechnik.com/trouble_shooting/ecuf20v.html#outs4

The engine harness earthing (ground) point(s) are on the C4 AAN intake manifold (2 locations near the rear). The engine is then grounded to the chassis via strap from the engine to the chassis leg, in the area under the C4 AAN turbo.

Other ground/earthing points are in the right and left side kick panels.

I have not done that yet.

Thanks for the earth point info

[UrS4boy]

Does anyone know the earthing point around the car?
Thanks

Have you done the ECU device stimulation check yet to establish that your ECU is talking to the N75?

http://www.sjmautotechnik.com/trouble_shooting/ecuf20v.html#outs4

The engine harness earthing (ground) point(s) are on the C4 AAN intake manifold (2 locations near the rear). The engine is then grounded to the chassis via strap from the engine to the chassis leg, in the area under the C4 AAN turbo.

Other ground/earthing points are in the right and left side kick panels.

[hunker7]

oh, how disappointing.

there's no chance of leaking around the hoses at the n75, wastegate etc??

Checked all the hoses around N75, replaced jubilee clips, same for moisture trap

MFTS or knock sensors?

If it was knock sensors, wouldn't engine run a bit rough when idling?


Does anyone know the earthing point around the car?

Thanks

[rynaqui]

MFTS does not impact boost on an AAN, unlike a 3B or ABY.

Learn something new every day, thanks Dave

[UrS4boy]

MFTS or knock sensors?

MFTS does not impact boost on an AAN, unlike a 3B or ABY.

[rynaqui]

MFTS or knock sensors?

[geneandbolly]

oh, how disappointing.

there's no chance of leaking around the hoses at the n75, wastegate etc??

[Error404]

It won't be the MAP or ECU I am sure.

[220bhp]

Knock sensor will cut boost ,and not always throw a code

[hunker7]

Not surprisingly N75 wasnt at fault. As usual, no easy fix for me. I've checked all the hoses i could, changed n75 so it's either map or ecu...Probably whichever is the most expensive one.